Musculoskeletal Injury in Professional Dancers: Prevalence and Associated Factors. An International Cross-sectional Study

by

Craig Loren Jacobs

A thesis submitted in conformity with the requirements for the degree of Master of Science

Graduate Department of Institute of Medical Science University of Toronto

© Copyright by Craig Loren Jacobs 2010

Musculoskeletal Injury in Professional Dancers:

Prevalence and Associated Factors.

An International Cross-sectional Study

Craig Loren Jacobs

Master of Science

Institute of Medical Science University of Toronto

2010

Abstract

Purpose: To determine the prevalence and factors associated with injury in professional ballet

and modern dancers, to explore dancers’ attitudes and perceptions of injury, and to assess if

dancers are reporting their injuries and reasons for not reporting injuries.

Methods: A cross-sectional survey was undertaken in professional ballet and modern dance

companies in Canada, Denmark, Israel, and Sweden.

Results: The point prevalence of injury in dancers is high (55% ballet; 46% modern) and most

have chronic pain. Years dancing professionally and rank were associated with injury in ballet

dancers. Attitudes towards injury vary and some dancers are continuing to dance when injured.

Greater than 15% of all injured dancers have not reported their injury.

Conclusions: Injury is common in dancers and there is an urgent need to investigate

interventions to help control injury and understand the long-term implications of these conditions

in this population.

ii

Acknowledgments and Contributions I wish to express my sincere gratitude to my supervisor Dr. J. David Cassidy for his guidance,

supervision, and scientific integrity and for providing me with such an important and exciting

research opportunity. I am truly grateful to my cosupervisor, Dr. Pierre Côté, for his belief in the

importance of my research. His excitement for research and science is truly infectious and

inspiring. I would like to thank Dr. Eleanor Boyle for her collaboration, contributions and

guidance with the statistical analysis. I am so grateful for her time, patience, and expertise. I

thank Dr. Carlo Ammendolia for his invaluable insights, input, and suggestions for my work. I

am so appreciative of my entire program advisory committee, each of whom has provided me

with guidance and inspiration.

This was a truly collaborative international effort that would not have been possible without the

contributions of Dr. Eva Ramel, Dr. Jan Hartvigsen, and Dr. Isabella Schwartz. They were

instrumental in applying for the ethics board applications in Sweden, Denmark and Israel

respectively. Dr. Ramel helped to develop relationships and communication with both the Royal

Swedish and Royal Danish Ballets. Additionally, Dr. Ramel’s previous scholarly work regarding

professional dancers has been an invaluable source of knowledge, and her willingness and

excitement to discuss dance health issues with me was extremely helpful. All three collaborators

reviewed the study questionnaire and made site specific recommendations. They provided me

with support during the survey completion in each country. They provided supplies, helped with

logistics and communication and gave me a greater understanding of social support and work

conditions in each country. I am so thankful for the amount of time and energy they have

contributed to this project.

Dr. Cesar Hincapié published the first systematic review of injury and pain in dancers which

served as a springboard and inspiration for my study. He guided me through the best evidence

synthesis systematic review update process and served as the second reviewer for all the

literature. I wish to thank him for that guidance and for his contribution to my research. I would

also like to thank Dr. Paula Stern for her encouragement over all these years, her role in the pilot

of the questionnaire, and for starting me off on this path. My deepest gratitude also goes to Dr.

Heather Shearer who has always been ready with advice and support whenever I needed it,

without question. I commend and thank Monica Alder for her wonderful design of the

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questionnaire which played an integral role in its success and appeal. The staff, scientists, and

students at CREIDO were so helpful over the years in so many ways, and I thank them all for

their input, suggestions, and incredible help.

Of course, this work would not have been possible without the participation of the dance

companies involved. I thank all the dancers, artistic staff, and administrative staff of the National

Ballet of Canada, Toronto Dance Theatre, Royal Swedish Ballet, Cullberg Ballet, Royal Danish

Ballet, Batsheva Dance Company and Ensemble, and the Kibbutz Contemporary Dance

Company and its junior company. I would like to especially thank those individuals from these

companies who facilitated the implementation and logistics of the study including Joanna Ivey,

Bridget Cawthery, Lars Anderstam, Jane Salier-Eriksson, Karen Bonnesen, Yaniv Nagar, Claire

Bayliss-Nagar, and Rachel Ariel.

I wish to thank all of the organizations who provided financial support for my research and

graduate studies: the Canadian Institutes of Health Research, the Artists Health Centre

Foundation, the University of Toronto, and the Canadian Memorial Chiropractic College. This

project was also partially funded by the Centre for Research Expertise in Improved Disability

Outcomes (CREIDO) which received substantial funding through a grant provided by the

Workers’ Safety and Insurance Board (WSIB).

I thank my parents, Michael and Shelley, for their never ending support and love. I am so

grateful to my partner Atsmon who has constantly reminded me of the importance of my work at

every stage and has been an incredible source of strength, encouragement, and love.

iv

Table of Contents

ABSTRACT.................................................................................................................................. II

ACKNOWLEDGMENTS AND CONTRIBUTIONS .............................................................III

TABLE OF CONTENTS .............................................................................................................V

LIST OF TABLES ..................................................................................................................... IX

LIST OF APPENDICES .......................................................................................................XI

LIST OF ABBREVIATIONS .................................................................................................. XII

CHAPTER 1: INTRODUCTION................................................................................................ 1

1.1 Statement of Problem ............................................................................................................. 1

1.2 Literature Review ................................................................................................................... 2

1.2.1 Screening for relevance...................................................................................................... 2

1.2.2 Critical review of the literature .......................................................................................... 3

1.2.3 Characteristics of musculoskeletal injury in dancers......................................................... 3

1.2.4 Prevalence and associated factors of musculoskeletal injury and pain in dancers. ........... 4

1.2.5 Incidence of and risk factors for musculoskeletal injury and pain in dancers ................... 8

1.2.6 Definition of Injury ............................................................................................................ 8

1.2.7 Injury Reporting............................................................................................................... 10

1.2.8 Assessment Tools for Musculoskeletal Injury and Pain in Dancers................................ 10

1.3 Environmental Scan of Healthcare and Social Programs................................................. 11

1.4 Summary and Rationale....................................................................................................... 13

1.5 Primary Objectives and Research Questions ..................................................................... 13

CHAPTER 2: METHODS AND MATERIALS ...................................................................... 15

v

2.1 Study design........................................................................................................................... 15

2.2 Source population/Setting ................................................................................................... 15

2.3 Inclusion/Exclusion Criteria ................................................................................................ 17

2.4 Recruitment/Survey Methodology ...................................................................................... 17

2.5 Description and Pilot-Testing of the Questionnaire .......................................................... 18

2.5.1 Description of the study questionnaire ............................................................................ 18

2.5.2 Pilot-testing of the study questionnaire............................................................................ 18

2.6 Measurement and Definition of Variables.......................................................................... 19

2.6.1 Sociodemographic variables ............................................................................................ 19

2.6.2 The Self-Estimated Functional Inability because of Pain (SEFIP) Questionnaire ......... 20

2.6.3 Eleven-point Numerical Rating Scale (NRS-11)............................................................. 21

2.6.4 Current Treatment and Pain Medication Use................................................................... 21

2.6.5 Injury Status/ Self Reported Injury .................................................................................. 21

2.6.6 Injury Characteristics ....................................................................................................... 21

2.6.7 Injury Reporting............................................................................................................... 22

2.6.8 Dancers’ Attitudes and Perception of Injury ................................................................... 22

2.6.9 Contextual Company Information ................................................................................... 22

2.7 Ethics...................................................................................................................................... 22

2.8 Statistical Analysis ................................................................................................................ 23

2.8.1 Data entry, double data entry, and data cleaning ............................................................. 23

2.8.2 Descriptive Statistics........................................................................................................ 23

2.8.3 Prevalence of Dance-related MSK Injury........................................................................ 23

2.8.4 Factors associated with MSK-injury in professional dancers.......................................... 24

CHAPTER 3: RESULTS ........................................................................................................... 25

3.1 Response rate......................................................................................................................... 25

3.2 Data entry error rate ............................................................................................................ 26

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3.3 Sociodemographic characteristics of the study population............................................... 26

3.4 Self Estimated Functional Inability because of Pain (SEFIP) scores............................... 30

3.5 Numeric Rating Scale Scores: Dance related pain over the last week. ............................ 34

3.6 Current treatment................................................................................................................. 37

3.7 Pain Medication Use ............................................................................................................. 42

3.8 Injury Prevalence.................................................................................................................. 43

3.9 Factors associated with self-reported dance-related musculoskeletal injuries (SRI) in

dancers. ........................................................................................................................................ 46

3.9.1 Univariate analysis (crude analysis) ................................................................................ 46

3.9.2 Multivariable analysis (logistic regression) ..................................................................... 50

3.10 Factors associated with SEFIP score of ≥3. ..................................................................... 51

3.10.1 Univariate analysis (crude analysis) .............................................................................. 51

3.10.2 Multivariable analysis (logistic regression) ................................................................... 56

3.12 Characteristics of Prevalent Injuries ................................................................................ 57

3.12.1 Body region injured ....................................................................................................... 57

3.12.2 Injury Duration............................................................................................................... 60

3.12.3 Injury Severity ............................................................................................................... 62

3.12.4 Time Off Work in Past Year.......................................................................................... 62

3.12.5 Recurrent Injuries........................................................................................................... 66

3.13 Relationship between SEFIP scores and SRI ................................................................... 68

3.14 Reporting of Dance-related Injuries ................................................................................. 68

3.15 Dancers’ Attitudes and Perceptions of Injury.................................................................. 73

3.16 Company Contextual Information .................................................................................... 80

CHAPTER 4: DISCUSSION ..................................................................................................... 82

4.1 Principal Findings................................................................................................................. 82

vii

4.2 Implications of Principal Findings ...................................................................................... 88

4.3 Strengths and Limitations.................................................................................................... 91

4.4 Future Directions .................................................................................................................. 94

CHAPTER 5: CONCLUSIONS ................................................................................................ 95

REFERENCES............................................................................................................................ 96

APPENDICES …………………………………………………………………..…………….100

viii

List of Tables Page

Table 1.1 Cross-sectional studies of prevalence and associated factors of

musculoskeletal injury and pain in dancers 6

Table 2.1 Number of eligible dancers in each dance company 16

Table 3.1 Response rates 25

Table 3.2 Sociodemographic characteristics of participating dancers:

age, sex, marital status, and low-income cut-offs. 28

Table 3.3 Characteristics of participating dancers: Body Mass Index,

low body weight, and years dancing. 29

Table 3.4 Country of Origin 30

Table 3.5 Frequency of SEFIP scores ≥ 3 (by company) 32

Table 3.6 Frequency of SEFIP scores ≥ 3 (by style, sex) 33

Table 3.7 Average dance-related pain over last week,

Numeric Rating Scale-11 scores 35

Table 3.8 Pain severity using Numeric Rating Scale-11 cut-points.

Average dance-related pain over last week 36

Table 3.9 Dancers currently receiving treatment for dance-related pain 38

Table 3.10 Treatment from Healthcare Practitioners (only dancers

currently receiving treatment) 39

Table 3.11 Frequency of Treatment from Healthcare Practitioners

(only dancers currently receiving treatment) 40

Table 3.12 Site of Current Treatment (only dancers currently receiving

treatment) 41

Table 3.13 Pain medication use in last week (all dancers) 42

Table 3.14 Current Injury Status 44

Table 3.15 Point prevalence of Self Reported Injury 45

Table 3.16 Point prevalence of SEFIP ≥3 Injury 45

Table 3.17 Univariate Analysis (ballet dancers only) – Self Reported Injury 47

Table 3.18 Univariate Analysis (modern dancers only) – Self Reported Injury 49

Table 3.19 Final Model for Logistic Regression Analysis. Factors Associated with Self Reported Injury (ballet dancers) 51

ix

Table 3.20 Univariate Analysis (ballet dancers only) – SEFIP score of ≥3 53

Table 3.21 Univariate Analysis (modern dancers only) – SEFIP score of ≥3 55

Table 3.22 Final Model for Logistic Regression Analysis. Factors Associated SEFIP score of ≥3 (ballet dancers) 56

Table 3.23 Body Region Injured (current most problematic injury of

injured dancers) by style and sex. 58

Table 3.24 Body Region Injured (current most problematic injury of

injured dancers) by company 59

Table 3.25 Duration of Injury (by style and sex) 61

Table 3.26 Duration of Injury (by company) 61

Table 3.27 Injury Severity (by style and sex) 64

Table 3.28 Injury Severity (by company) 64

Table 3.29 Time off work due to current injury in past year (by style and sex) 65

Table 3.30 Time off work due to current injury in past year (by company) 65

Table 3.31 Recurrent Injury (by style and sex) 69

Table 3.32 Recurrent Injury (by company) 67

Table 3.33 Highest Reported SEFIP Score for Injured and Non-injured

Dancers 68

Table 3.34 Frequency of non-reported injuries 69

Table 3.35 Reasons for not reporting an injury 70

Table 3.36 To whom are dancers reporting their injuries? 71

Table 3.37 Injuries Reported as Work Injuries 72

Table 3.38 Responses to Attitudinal Questions 75

Table 3.39 Company Contextual Data for the 2007-08 Season 81

x

List of Appendices Page

Appendix 1 Electronic Database Search Strategies 100

Medline 101

Cinahl 102

Appendix 2 Study Questionnaire 103

Appendix 3 Research Ethics Board Approvals 119

University of Toronto 120

University Health Network 121

Hadassah Hospital (Israel) 122

Datatilsynet (Denmark) 123

Regional Ethics Committee, Lund (Sweden) 128

Appendix 4 Copyright Acknowledgement 130

xi

List of Abbreviations

B: Ballet

BAT: Batsheva Dance Company

BJHS: Benign joint hypermobility syndrome

BMI: Body mass index

CAD: Canadian dollar

CI: Confidence interval

CUL: Cullberg Ballet

ENS: Ensemble Batsheva

KDC: Kibbutz Contemporary Dance Company

KDC2: Kibbutz Contemporary Dance Company 2

M: Modern

MD: Medical doctor

Med: Median

MSK: Musculoskeletal

NA: Not available

NBC: National Ballet of Canada

ND: No data

NRS: Numeric rating scale

NSAIDs: Non-steroidal anti-inflammatory drugs

OR: Odds ratio

P: Professional

PP: Pre-professional

RDB: Royal Danish Ballet

RSB: Royal Swedish Ballet

SD: Standard deviation

SEFIP: Self Estimated Functional Inability because of Pain Questionnaire

SRI: Self-reported injury

TDT: Toronto Dance Theatre

U: University

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xiii

WSIB: Workers’ Safety and Insurance Board

YS: Young student

β: Beta

ρ: Rho (Spearman’s rank correlation coefficient)

Chapter 1: Introduction

1.1 Statement of Problem

Dancers are both artists and athletes. Professional dancers train many years, often from a

young age, to attain one of the few positions available in professional dance companies.

They are subjected to fierce competition from other talented dancers, as well as intense

scrutiny from teachers, choreographers, and artistic directors. They must possess innate

talent, yet obtain a high level of skill and physical ability. In one study comparing ballet

to 61 other sports, it was deemed the second most demanding physical activity on par

with bullfighting and second only to football.1

The number of professional modern and ballet dance companies in any one country is

small. Therefore, dancers from around the world compete for the few positions available

in these companies. This often results in a very internationally diverse work population.

Competition does not end once the dancer achieves a professional dance position.

Professional ballet dance companies have a ranking system. Most dancers start in the

corps de ballet and try to work their way up to soloist and then principal dancer positions.

Although modern dance companies may not employ a ranking system, dancers still

compete for roles. Injury or pain may impede a dancer’s ability to attain or maintain their

position or roles in a company and, at worst, drastically shorten a dancer’s career. The

professional dancer’s career is extremely short with most dancers retiring from

performance in their mid to late 30s in the United States of America and between the ages

of 41-44 in Sweden. 2, 3

A recent systematic review has found the dance medicine literature regarding

musculoskeletal injury and pain to be “young and heterogeneous” identifying only 32

published articles as scientifically acceptable. 4 The prevalence of musculoskeletal

(MSK) injury in professional dancers ranges from 20-84% while the prevalence of MSK

pain is as high as 95%.4 This broad range of prevalence estimates is likely due to

different definitions of injury and study methodology. The paucity of high quality studies

1

2

for an occupational group which is at high risk for MSK injury and pain points to the

importance of further research in this area. The objective of my thesis is to add to the

existing literature on the burden and associated factors of MSK injury and pain in

professional ballet and modern dancers by updating a systematic review of the literature

and by surveying professional dancers from Canada, Sweden, Denmark, and Israel.

1.2 Literature Review

A systematic review of the entire dance medicine literature up to 2004 was performed by

Hincapié et al.4 Two themes were identified: (1) MSK injuries and pain; and (2)

metabolic and nutritional disorders. With the first author of that study, I updated this

review dealing with MSK injuries and pain to 2008 using an identical search strategy

(Appendix 1). The primary sources of literature were the electronic databases MEDLINE

(2004 to March 2008) and CINAHL (2004 to March 2008). Indexed terms and text words

such as dance, dancer, dancing, athletic injuries, occupational injuries, sprains and

strains, musculoskeletal diseases, bone density, menstruation disturbances, eating

disorders, and others were used to search the databases. 4 Additionally, I examined the

reference lists of all relevant studies for additional or unpublished literature.

1.2.1 Screening for relevance

Using a best evidence synthesis approach,5, 6we each independently screened all of the

citations that were identified through the search strategy and using the previous review’s

criteria included: “English language reports; published reports of original research,

systematic reviews, conference proceedings, government reports, guidelines, or

unpublished “grey literature” manuscripts; studies containing original raw data on at least

20 human research participants, including a control group if present; studies examining

the prevalence, incidence, associated factors, risk factors, diagnosis, interventions,

economic costs, prognosis, or other aspects of MSK injury and pain, and metabolic and

nutritional disorders in dancers; and, studies of dancers in any form of artistic dance such

as ballet, modern, tap, theatrical, folk, Flamenco, break-dancing, ballroom dancing, and

ice dancing”.4 Using identical exclusion criteria to the previous review, we excluded:

3

“studies on recreational or exercise forms of dance such as aerobic dancing or social

dancing in clubs, parties or raves; studies on the cognitive, behavioral or learning aspects

of dance; narrative, editorial or clinical reviews, opinion papers, letters to the editor, and

editorials; studies of conditions with questionable clinical relevance or asymptomatic

presentation; studies using cadavers or non-human subjects; and, studies reporting

findings not specific to dancers (e.g., studies where dancers’ information was combined

with other athletes’ information and results could not be evaluated specifically for

dancers)”.4

The first author of the previous review and I independently evaluated each citation’s

relevancy through a two-level screening process. We obtained and reviewed all papers

that were identified as probably relevant, or of unknown relevance in the first level of

screening. In the second-level screening, these were then classified as either relevant or

irrelevant to the systematic review.4

We maintained the 2 themes from the previous systematic review: (1) MSK injuries and

pain; and, (2) metabolic and nutritional disorders. For the purposes of this thesis, I will

extract and include information relevant to the first theme, MSK injuries and pain.

1.2.2 Critical review of the literature

We critically appraised all relevant studies for scientific merit and clinical relevance by

using a priori criteria and computer-based critical review forms.7 Studies were

considered scientifically admissible or scientifically inadmissible on the basis of the

presence of fatal biases and methodological flaws. We undertook a full discussion of each

paper focusing on issues such as design, study population, study conduct, participation

and follow up rates, measurement and analysis.4 I have extracted relevant information

from the accepted papers, and my update of the review for this thesis focuses on studies

relevant to professional ballet and modern dancers.

1.2.3 Characteristics of musculoskeletal injury in dancers

The previous review of MSK injuries in dancers reported that most MSK injuries in

dancers are soft tissue injuries such as sprains, strains, and tendinopathies primarily

4

affecting the lower extremities and back.4 Many studies in my updated review did not

report exact locations of injuries measured; however, of those that did, lower extremity

injuries still predominated followed by hip and low back injury. Three studies accepted in

the review update focused on specific injuries including snapping hip syndrome, ankle

injuries, and acute hamstring strain.8-10

1.2.4 Prevalence and associated factors of musculoskeletal injury and pain in

dancers.

Hincapié’s review identified six studies that focused on professional dancers and three

studies that included both professional, preprofessional, and/or university level dancers.

All of these studies included ballet dancers while only two of the studies included modern

dancers.4 In my review update, I identified one study that focused solely on professional

ballet dancers,11 one study on professional modern dancers,12 and one study that focused

on a mix of professional ballet dancers and elite ballet students.10

Prevalence estimates varied according to time periods and case definitions with estimates

ranging from 20% to 95%. Two of the better quality studies reported the 1-year period

prevalence of MSK pain in professional Swedish ballet dancers to be approximately 95%,

with 90% of those dancers who were followed up 6 years later reporting recurrent pain.13-

15 One study reported the point prevalence of minor recurrent injury in professional

ballet and modern dancers to be 89%.16 Another study reported the point prevalence of

chronic injury in professional ballet and modern dancers at 48% and the six month period

prevalence of injury at 42%.17 The majority of studies reported 12-month or lifetime

prevalence increasing the likelihood of recall bias.

Eight of the eleven identified cross-sectional studies reported on factors associated with

MSK injury or pain in professional dancers. Factors reported to be positively associated

with MSK injury or pain include older age18, female sex 14, male sex 19, years of dance

experience18, 20, “overachiever” personality traits18, dance setting17, performance level14,

20, hours of training per day21, menstrual dysfunction21, muscular tension before

performing14, work dissatisfaction14, joint hypermobility19, and psychological

5

factors(stress, anxiety, depression, anger, fatigue and confusion)11. The majority of these

associations are preliminary in nature. Only one study of professional ballet and modern

dancers made use of multivariable statistical methods in assessing the independence of

these associated factors.14 In Table 1.1, I outline the cross-sectional studies of

professional ballet and modern dancers with reported prevalence estimates and associated

factors.

6

Table 1.1: Cross sectional studies of prevalence and associated factors of musculoskeletal injury and pain in dancers Prevalence Estimates Study;Country Style;Level Study Size

(N); Response Rate

Age (y) Outcome Point 6 month

12 month

Lifetime Associated Factors

Chmelar et al.16; USA

B,M; P,U 39 (18 Professional dancers); 64%

18-37 Injury 74% (minor injury); 89% P only

ND 23% (major injury)

ND NA

Hamilton et al.18; USA

B; P 29; 64% 22-41 Injury ND ND ND 20-79% Age, years of dance, personality traits

Bowling17; UK B,M; P 141; 75% >18 Injury 48% (chronic)

42% ND 84% Dance setting

McNeal et al.20; USA/Canada

B; P,PP,U,YS

350 (99 professional dancers); 80-100%

<13 and ≥13

Injury ND ND ND 20-80% Years of dance, performance level

Kadel et al.21; Sweden

B; P 54; 55% NA Stress fracture

ND ND ND 32% Hours of training per day, menstrual dysfunction

Ramel and Moritz14; Sweden

B; P 64; 84% 17-47 Pain ND ND 69-94%

ND Sex, performance level, muscular tension before performing, work dissatisfaction

Abbreviations: B, ballet; BJHS, benign joint hypermobility syndrome; M, modern; NA, not available; ND, no data; P, professional; PP, preprofessional; U, university; YS, young student.

7

Table 1.1: Cross sectional studies of prevalence and associated factors of musculoskeletal injury and pain in dancers Prevalence Estimates Study;Country Style;Level Study Size

(N); Response Rate

Age (y) Outcome Point 6 month

12 month

Lifetime Associated Factors

Ramel and Moritz13 and Ramel et al.15; Sweden

B; P 128; 87% 51; 60%

17-47 Pain ND ND 61-95%

ND Nonassociated factors: age, sex, workload

McCormack et al.19; England

B; P,PP 287 (71 professional dancers); NA

NA Injury NA (study focused on hypermobility and BJHS)

Sex, joint hypermobility

Adam et al.11; Germany

B; P 54; 78% NA Injury NA ND 87% ND Stress, sleep problems, negative mood states

Scialom et al.12; Brazil

M; P 30; 75% NA Injury ND ND ND 47% NA

Winston et al.10: Canada

B; P,PP 87; 92% >16 Snapping hip syndrome

ND ND ND 91% Movements associated with snap: Grand battement à la seconde (42%), grand plié (25%), développé à la second (22.8%).

Abbreviations: B, ballet; BJHS, benign joint hypermobility syndrome; M, modern; NA, not available; ND, no data; P, professional; PP, preprofessional; U, university; YS, young student.

8

1.2.5 Incidence of and risk factors for musculoskeletal injury and pain in dancers

In the review of Hincapié et al., eight cohort studies of professional dancers were identified.

Only one study focused on professional modern dancers. Five studies focused on professional

ballet dancers and two studies examined both professional ballet dancers as well as university or

high school level ballet students.4 In my review update, I identified an additional five cohort

studies of dancers; however, only one study included professional ballet dancers along with

university and high-school level dancers. The remaining four studies included only university or

preprofessional dancers.

The cumulative incidence of musculoskeletal injury in professional dancers ranged from 40% to

94%; however, the follow-up periods varied between studies.4, 22Four studies reported incidence

densities. One study of professional ballet dancers reported 0.65 injuries per dancer-year.23 A

study of ballet dancers in Sweden reported 0.62 injuries per 1000 dance-hours.24 A study of

modern dancers in the United States evaluating an injury management program reported

incidence per 1000 dance-hours as 0.51, 0.48, 0.57, 0.29, and 0.18 for each respective five years

of the study.25 Lastly, a study of ballet dancers in Norway reported 3.2 injuries per dancer for a

five-month follow-up period.26

Risk factors positively associated with musculoskeletal injury and pain that were reported in

these cohort studies include age24, female sex for overuse injuries and male sex for acute knee

and upper limb injuries23, 24, 27, 28, seasonal timing26, prior injury29, fatigue30, frequency/intensity

of training30, psychological characteristics associated with eating disorders30, dieting30 and

psychosocial coping31. Nonassociated factors included age27, 28, sex25, rank27, 28, stress/tension26,

and feeling of influence on working conditions26. The majority of these studies explored crude

associations and therefore these associations are preliminary in nature and may not be

independently associated with injury. Only two studies made use of multivariable and/or

stratified analysis to determine independent associations with injury.25, 31

1.2.6 Definition of Injury

In their systematic review of the literature, Hincapié et al found that the definition of an “injured

dancer” varied considerably.4 In many studies, no definition was provided, while others

9

restricted their sampling to dancers with compensable injuries by the Worker’s Compensation

Board. Some studies restricted their definition to injuries that required attention by a health care

professional. Overall, Hincapié et al reported that definitions tended to be vague. This vagueness

is illustrated in one study that defined a dance injury as “one that affected the dancer’s dancing in

some way”, or as an event resulting in financial outlay by the company.4 My update to this

review found that the majority of studies did report on their use of a specific definition of

musculoskeletal injury in dancers.8, 11, 12, 31-34 Of those that reported a definition of injury, they

were more uniform than the definitions reported in the previous systematic review incorporating

either a time-loss or functional component to the definition.

The International Association of Dance Medicine and Science’s Standard Measures Consensus

Initiative is in the process of making recommendations on how to measure and define injury.35

Similarly, Bronner et al have proposed a uniform reporting guideline that includes a standardized

definition of injury based on existing reporting systems for athletes.36 The International

Performing Arts Injury Reporting System instrument uses a definition of injury based on time-

loss from dance activity.35 However, Bronner’s proposal calls for a broader definition of injury

that encompasses any physical complaint resulting from dance-related activity.36 Dance UK, a

British organization for dancers, defines injury as “… a physical problem deriving from stress or

other causes to do with performance, rehearsal, training, touring or the circumstances of dance

life, which affects your ability to participate fully in normal training, performance or physical

activity”.37 To date however, there is no consensus of a definition of injury amongst dance health

practitioners and researchers.

While some advancement has been made regarding the definition of injury, we still know little

about how dancers perceive and cope with musculoskeletal injury. No study in the systematic

review, or my update of the review, has reported on professional dancers’ attitudes and

perceptions of injury.4, 22 Knowledge and understanding of injury from the dancers’ perspective

will help to inform both researchers and health care practitioners dealing with dance injuries. A

recent qualitative study of modern dance students, teachers, community dancers, professional

dancers, and former dancers reports that half of the participants defined injury as “something that

stopped them from dancing or from moving normally.” The second most common response was

“an injury caused by a particular type, quantity, or location of pain”, although the two statements

10

were not always mutually exclusive. A minority of the participants defined injury solely as an

acute event accompanied by visual signs such as swelling and bruising.38

1.2.7 Injury Reporting

Few studies have addressed the issue of injury reporting in professional dancers. One cross-

sectional study reported that between 15-30% of dancers who are injured do not seek medical

attention.20 Psychological issues that may cause a dancer to “dance through” or with pain or

injury include the fear of losing a role, losing their job, being considered unreliable, or pressure

by the company to perform rather than cancel a performance.39 A British study reports that only

32% of professional dancers stopped and rested after an injury occurred, with the majority of

dancers continuing to dance as best they could with no rest.17 Of 376 different dance-related

injuries treated by a naprapath employed by the Stora Theatre in Gothenburg over a three year

period, only 20 injuries were officially reported. These non-reported injuries included injuries as

varied as non-specific neck pain to stress fractures.13 In one Swedish study more than half of the

dancers reported that they had worked on several occasions when they felt they should not have

due to injuries, fatigue, or illness.40 For many reasons, dancers may be dancing through or past

what health care providers consider an injury. The issue of non-reporting of injuries is very

important, as it could bias all measures of incidence or prevalence of musculoskeletal injuries in

dancers. More importantly, this could lead to long-term health consequences for injured dancers.

Hincapié et al recommended in their systematic review that further research is needed to

determine how commonly musculoskeletal injury is not being reported by dancers to their

respective dance companies and the reasons dancers are not reporting their injuries.4

1.2.8 Assessment Tools for Musculoskeletal Injury and Pain in Dancers

Hincapié et al identified one study of a diagnostic and assessment tool for musculoskeletal pain

and functional limitation.4, 40 The Self Estimated Functional Inability because of Pain (SEFIP)

questionnaire is a tool developed specifically for dancers based on the Nordic Musculoskeletal

Questionnaire. The SEFIP is a validated questionnaire created specifically for dancers, and has

good agreement with actual pain and dysfunction found on physical examination.40 The SEFIP is

described further in section 2.6.2.

11

1.3 Environmental Scan of Healthcare and Social Programs

I have performed an environmental scan of healthcare and social programs in nine professional

dance companies in Canada, Israel, Denmark, and Sweden by interviewing the artistic and

administrative staff of each company. An environmental scan provides information of internal

and external conditions about an organization.41 Each of these countries has a publicly funded

national healthcare system; however, coverage of care for dance-related injuries varies in each

country as well as in each company. Physiotherapy and other paramedical services are not

covered by the public health system in Ontario. The National Ballet of Canada and the Toronto

Dance Theatre both supply extended health care coverage to their dancers which covers these

services up to a certain amount. Additionally, the National Ballet of Canada has on-site

physiotherapy available at no cost to the dancers and a medical doctor is available on-site one

day each week. Dancers in the Toronto Dance Theatre must receive physiotherapy or other

paramedical services off-site, and then seek reimbursement from their extended health care

insurance.

Israel’s health care system does cover physiotherapy and other paramedical services. The

Batsheva Dance Company and Ensemble (Israel) does not have on-site healthcare, but has a

physiotherapist associated with the company. Visits to this specific physiotherapist are covered

by the company without restriction of number of visits. Additionally, the company provides an

option for each dancer to seek physiotherapy or other paramedical services such as chiropractic

care, massage therapy, or acupuncture from a roster of practitioners up to a maximum of 23

treatments per season. The Kibbutz Contemporary Dance Company (Israel) and its junior

company provide on-site physiotherapy, massage and acupuncture three times a week at no cost

to the dancer.

The Royal Swedish Ballet provides on-site physiotherapy and naprapathic care at no cost to the

dancers. A nurse is available on-site everyday and an orthopedic and ear, nose, and throat

specialist are available on-site one day a week. Dancers may also seek off-site paramedical

treatment up to a limit of 900 Swedish Kroner ($130 CAD) per year. The Cullberg Ballet

(Sweden) does not have on-site care, but pays for all care sought externally for its dancers. Non-

injured dancers are limited to one treatment per week.

12

Denmark provides partial coverage for physiotherapy and paramedical services; however, the

Royal Danish Ballet has the most extensive on-site healthcare available for its dancers of all the

companies I interviewed. Services provided on-site to the dancers at no cost include:

physiotherapy, massage, sports psychology, medical doctor, orthopedic specialist, dietician, and

special “sick classes” for injured dancers. The company will also reimburse 50% of the cost for

off-site treatment if this is approved in advance.

Workers’ compensation coverage varies by country and company as well. The Toronto Dance

Theatre dancers are covered by the provincial Workplace Safety and Insurance Board (WSIB);

however, the National Ballet of Canada dancers are not covered by the WSIB. Dancers in both

companies have long term disability plans provided by the company. Israel has a National

Insurance (Bituach Leumi) which is accessed if the dancer is disabled due to a work related

injury. The Batsheva Dance Company and Kibbutz Contemporary Dance Company additionally

provide their dancers with optional private disability insurance. Scandinavian countries are well

known for their social support programs for injured workers. Swedish dancers are covered by the

national workers’ compensation insurance. It should be noted that non-Swedes working in

Sweden are entitled to the same benefits. The company pays an injured dancer’s salary for two

weeks after which it is paid by the national insurance. Sweden is moving towards a new system

with additional limitations. Dancers’ work injuries in Denmark are also covered by a national

insurance. Similar to Sweden, injuries are reported after two weeks to the national insurance.

Employment security also varies drastically between companies and countries. The Scandinavian

companies again have the strongest employment security. Once a dancer is employed by a

Swedish or Danish dance company for three years, they obtain permanent lifetime employment.

Swedish dancers can then take a leave of absence for up to three years if desired (for example to

work elsewhere) and have guaranteed employment upon return. Swedish and Danish dancers

may retire at the age of 40 with pension. In the Israeli companies, employment is on a season by

season basis, however dancers are employed year round. In the Canadian companies, dancers are

hired seasonally and most are “laid off” in the summer months. No pensions exist for Israeli or

Canadian dancers.

13

1.4 Summary and Rationale

Informed by the systematic review of the dance medicine literature and my update to this

systematic review, it is apparent that information is still lacking in regards to professional

dancers and musculoskeletal injury and pain. Multivariable analysis has rarely been used to

determine the independence of factors associated with injury in professional dancers.

Additionally, very few studies have included or focused on professional modern dancers, who

are also at risk for musculoskeletal injury that might have long-term consequences for their

future health.

A need for information regarding professional dancers’ attitudes and perceptions of injury exists.

Dance health practitioners and researchers have yet to come to a consensus on the definition of a

dance injury. Understanding injury from the dancers’ perspective could inform future research to

better capture all potentially injured dancers and provide a clearer and more comprehensive

picture of dance injuries overall.

Lastly, it is apparent that for many reasons dancers may be wary to report an injury. The

understanding of reasons why dancers may not report an injury can help the development of

future research methodology to provide better prevalence and incidence estimates. The reporting

of injury also may vary between companies and countries with varying levels of social and

medical support for dancers.

With these issues in mind, I undertook an international cross-sectional survey based study of

professional ballet and modern dancers in Canada, Denmark, Israel, and Sweden.

1.5 Primary Objectives and Research Questions

The primary objective of my research is to determine the point prevalence of dance-related

musculoskeletal injury in professional ballet and modern dancers and the factors associated with

these dance-related injuries.

The secondary objectives of my research are:

1. To report the characteristics and patterns of these dance-related injuries.

2. To explore professional dancers’ attitudes and perceptions of injury.

14

3. To assess if professional dancers are not reporting injuries and why they might not report

their injuries.

CHAPTER 2: Methods and Materials

2.1 Study design

This study is a cross-sectional survey of professional ballet and modern dancers in Canada,

Sweden, Denmark and Israel.

2.2 Source population/Setting

Participants were recruited from three professional ballet and six modern dance companies in

Canada, Sweden, Denmark and Israel. Due to the small number of professional dance companies

in each country, I aimed to recruit companies in multiple countries in order to increase sample

size. Working with research and dance contacts in these countries, I approached the directors of

various dance companies with an aim to recruit the largest modern and ballet companies in each

country as part of this convenience sample. Participating ballet companies included the National

Ballet of Canada, the Royal Swedish Ballet and the Royal Danish Ballet. Participating modern

dance companies included the Toronto Dance Theatre (Canada), the Cullberg Ballet (Sweden),

the Batsheva Dance Company (Israel), the Batsheva Ensemble (Israel), the Kibbutz

Contemporary Dance Company (Israel), and the Kibbutz Contemporary Dance Company 2

(Israel). Table 2.1 outlines the total number of dancers eligible for participation in each

company.

The participating companies were chosen as they represent the highest standard of ballet or

modern dance in that country and are recognized as premier companies in each country and

internationally. All three ballet companies are considered the “national” ballet company of the

country and have a full range of classical ballets in their repertoire. In addition, the National

Ballet of Canada and the Royal Danish Ballet have incorporated neoclassical and contemporary

works into their repertoire. The modern dance companies each have a “house” choreographer

and primarily dance works by that choreographer as well as additional repertoire by guest

choreographers.

All the dance companies have very similar workday schedules. This begins with a company class

(1 to 1¼ hours) to prepare for the workday followed by 6 hours of rehearsal on a non-

performance workday. All three ballet companies begin the day with a ballet class while the 15

16

modern companies begin with either a modern or ballet class. Work days on which performances

take place vary slightly with a later start for evening performances and shorter rehearsal times.

Table 2.1 : Number of Eligible Dancers in Each Dance Company Number of Eligible Dancers

Ballet Companies:

National Ballet of Canada 69

Royal Swedish Ballet 67

Royal Danish Ballet 83

Modern Dance Companies:

Toronto Dance Theatre 16

Cullberg Ballet 20

Batsheva Dance Company 20

Batsheva Ensemble 15

Kibbutz Contemporary Dance Company 17

Kibbutz Contemporary Dance Company 2 12

Total Number Eligible Dancers: 319 Eligible = employed by dance company at time of study, age ≥18, not on leave of absence to dance in another company (only Scandinavian companies), not character dancer. See section 2.3 for further detail.

17

2.3 Inclusion/Exclusion Criteria

Any dancer employed by the participating dance companies at the time of data collection was

eligible to participate with the exclusion of dancers younger than eighteen years of age due to

issues of consent. Dancers who had taken an extended leave of absence to dance in another

company and were not presently dancing with their company were also excluded. This would

only be an issue in the Scandinavian companies where dancers are able to take a three year leave

of absence in order to dance with another company while maintaining their employment status

with the original dance company. The company management was instructed not to forward a

questionnaire to these dancers. Character dancers were also excluded as their work hours and

current dance exposure is very different than the other dancers. Character dancers often are older

dancers in ballet companies and have roles with more mime and gesture type of movements,

rather than the strenuous dance of the other company members.

2.4 Recruitment/Survey Methodology

A date for survey distribution was arranged with the company management. A common time in

the season for data collection was not possible to arrange due to the complex touring and

performing schedules of all companies involved. Companies were instead asked to arrange a

time for the survey distribution which would occur during a period in which performances were

taking place and that did not occur immediately after vacations or holidays. This was done in

order to make the dance exposure as uniform as possible with various companies and repertoires.

Additionally, company managers and directors had noted that performance periods seemed to be

the periods in which more dancers were injured. To encourage participation, a 45-minute time

for survey completion was scheduled during the regular workday in which all dancers would be

present. This eased the burden on the dancers as it took place either after company class or after

a rehearsal which involved all the dancers.

A brief explanation of the purpose of the study as well as the informed consent process took

place prior to the distribution of the survey. Neither company management nor artistic personnel

were present during the survey distribution, so dancers would not feel pressured to participate.

The company management was not aware of which dancers did or did not participate in the

study. One investigator who was familiar with the study and spoke the native language of the

country was present to clarify any questions. All dancers received a study package that included

18

a study questionnaire, an introductory letter and a pre-stamped addressed envelope. Participation

was voluntary and the dancers were instructed not to write any identifying information on the

questionnaire. Dancers were given the option to complete the survey during the time provided or

at their own convenience. Upon completion, they were asked to seal their completed

questionnaire in the provided envelope and return it to a locked drop box on site or by post. All

dancers not present on the day of the survey were forwarded a study package by the company to

ensure that dancers who were off work due to illness or injury would have the opportunity to

participate. Bulletin board and/or email reminders were utilized to remind dancers who had not

yet responded to return the survey to the drop box or by post.

2.5 Description and Pilot-Testing of the Questionnaire

2.5.1 Description of the study questionnaire

The study questionnaire (Appendix 2) consists of two parts. The first part is the Self Estimated

Functional Inability because of Pain (SEFIP) questionnaire. It is the only published tool

developed and validated specifically to measure musculoskeletal pain and function in dancers.40

The second part consists of five sections (A-E). Section A consists of 7 items dealing with

current dance-related pain, injury, and treatment and includes Numeric Rating Scales (NRS).

Section B contains 7 items dealing with the effect and burden of dance-related pain over the past

six months. Section C contains 9 attitudinal questions regarding dancers’ perception of

musculoskeletal injury and one question regarding their current injury status. Section D contains

11 items specific to the dancers’ current injury. Lastly, section E consists of 16 demographic

questions.

2.5.2 Pilot-testing of the study questionnaire

The development and pilot-testing of the study questionnaire was performed prior to my

enrollment at the University of Toronto and therefore is not an official component of my thesis.42

However, a brief description of the process is essential. The study questionnaire was developed

and pilot-tested using standard questionnaire development methodology.43 An environmental

scan and literature review was performed. The pilot questionnaire was evaluated by two

epidemiologists with expertise in survey development for face validity. An expert in dancers’

health evaluated the questionnaire for face and content validity and to ensure the questionnaire’s

applicability in an international setting. The survey was also evaluated by one dance company

19

manager and one rehearsal director in Israel to ensure the information would be useful and

relevant to primary stakeholders. The questionnaire was then pilot-tested on nine dancers from

the National Ballet of Canada. Twenty-two percent of the items needed revision or clarification

based on incorrect answers, absent answers, or written feedback from the dancers. All

ambiguous, problematic or double-barreled questions were identified and revised by consensus

amongst the thesis committee members. Discussion with the participating dance companies

revealed that the working language in each company was English. Therefore, I decided to

administer the questionnaire only in English. The revised questionnaires were sent to co-

investigators in Sweden, Denmark and Israel. These investigators were requested to provide

further input and identify any questions or words that may be confusing. Therefore cross-cultural

face validation was achieved by addressing these issues. A specific questionnaire was developed

for each distinct country. All questions were the same, however country specific units (i.e.

currency) and translations in parentheses were provided for words which were identified as

potentially confusing by the coinvestigator for that country.42

2.6 Measurement and Definition of Variables

2.6.1 Sociodemographic variables

Sociodemographic variables from the study questionnaire used to describe the study population

and to estimate their association with dance injury include: age, sex, height, weight, and before-

tax yearly or monthly income (Appendix 2 Section E). Body mass index (BMI) was calculated

from the height and weight variables using the formula: BMI = kg/m2. Low BMI levels were

defined as <18.5 based on Canadian Guidelines for Body Weight Classification in Adults.44

Low-income cut-offs were obtained or calculated from the official statistical authority of each

country. Low income cut-off points defined for each country are: Canada, <20,778 Canadian

Dollars/year45; Sweden, <140,400 Swedish Krona/year (20,140 CAD)46; Denmark, <100,000

Danish Krone/year (20,310 CAD)47; Israel, <3,710 Israeli New Shekel/month (1,025 CAD)48.

Dance specific characteristics are: number of years in present dance company, number of years

dancing professionally, number of years dancing total, and rank in the company (Appendix 2

Section E). Number of years dancing professionally was defined as: the dancer received payment

for work as a dancer either in a dance company or freelance. Number of years dancing total was

defined as: dance training at least three times per week plus professional experience.

20

2.6.2 The Self-Estimated Functional Inability because of Pain (SEFIP) Questionnaire

The SEFIP is the only validated diagnostic and assessment tool for dancers

identified in the dance medicine literature.4, 40 The SEFIP is an English language questionnaire

based on the Nordic Musculoskeletal Questionnaire and measures the intensity of current pain as

well as ability to dance on a 5-point scale for 14 distinct body regions40. These points are: 0 =

“very well”; 1 = “some pain but not much problem”; 2 = “pretty much pain but I can handle it”;

3 = “much pain, must avoid some movements”; 4 = “cannot work in the production because of

pain”. The SEFIP was validated by Ramel et al using a test-battery for pain and muscular

dysfunction designed for dancers.40 Overall good agreement was demonstrated between the

SEFIP and the test-battery. The mean agreement was 88% with a range of 75% (hips) to 96%

(neck) and a mean kappa value of 0.69. The sensitivity and the specificity were calculated for

each body region. The mean sensitivity and specificity of the SEFIP over the body regions is

72% and 86% respectively. This rises to 86% and 88% respectively if shins, elbows and wrists

were excluded. The authors concluded that any dancer with a score of 2 or greater should be

referred for physical examination by a healthcare practitioner. Of the 14 body regions with an

intensity of 3 or more in Ramel’s work, 13 were found to have positive findings in the test

battery. Ramel et al additionally report that of the 31 painful areas without positive findings in

the test battery, only one of these had a SEFIP score of 3, while seven had a SEFIP score of 2,

and 23 had a SEFIP score of 1.40

The SEFIP is scored on a scale of 0 – 4 for each body region (Appendix 2, Page 106). The

authors also suggest that a sum score may be reported to look at a company’s overall

musculoskeletal pain and function burden at different time periods. One would add all the body

regions to obtain a score out of 64 points for each dancer using a maximum score of 4 for 16

body regions.40 However, as I was not repeating the test for each company, I have chosen not to

report a sum score, but to focus on the individual scores for each body part. This is essential as a

dancer may have a very high score in one body region, but an overall low sum score. A score of

3 represents significant pain accompanied by functional modification of movement. I have

therefore chosen to report SEFIP scores of 3 or more in order to reflect the percentage of dancers

with a functional component associated with their dance-related pain. Additionally, I use a

SEFIP score of 3 or more as an additional or alternative outcome measure of injury prevalence in

addition to self-reported injury.

21

2.6.3 Eleven-point Numerical Rating Scale (NRS-11)

The Eleven-point Numerical Rating Scale (NRS-11) was used to measure average dance-related

pain over the last week (Appendix 2, Section A). This scale is valid and reliable.49, 50 Cut-points

of four and seven were used to differentiate between “mild”, “moderate”, and “severe” pain.50

2.6.4 Current Treatment and Pain Medication Use

Dancers were asked whether they are currently receiving treatment, the type of practitioner they

are receiving care from, and if their treatment was on or off-site. Dancers were additionally

asked to report on their use of prescription and non-prescription pain medication in the past week

for dance-related pain (Appendix 2, Section A).

2.6.5 Injury Status/ Self Reported Injury

I have used Bronner’s definition of injury, “any physical complaint sustained by a dancer

resulting from company performance, rehearsal, or technique class, irrespective of the need for

medical attention or time-loss from dance activities” as a working definition of injury for the

purposes of this study.36 The pilot study indicated that dancers had difficulty reporting

themselves as solely either “injured” or “not injured”.42 I have therefore evaluated dancers’

perception of their injury status by asking them to choose from the following variables:

“injured”, “recovering from an injury”, “suffering from a persistent injury”, or “not injured”

(Appendix 2, Section C). As I was also collecting information regarding dancers’ attitudes and

perceptions of injury, I purposefully did not define injury for them. This qualitative information

will be analyzed in a future paper and asks about definitions of injury in open-ended questions.

For the purposes of this study, any dancer choosing “injured”, “recovering from an injury”, or

“suffering from a persistent injury” will be considered “injured” and reported as self reported

injury (SRI).

2.6.6 Injury Characteristics

Variables chosen as injury characteristics include: dance or non-dance related injury, duration of

injury, severity of injury, time-off due to injury, previous injury occurrence, and time of previous

injury occurrence (Appendix 2, Section D). These injury characteristics have been measured for

self-reported injury.

22

2.6.7 Injury Reporting

Dancers with self-reported injury were asked if they have reported their injury and if so, to

whom they have reported their injury. Those dancers that did not report their injury were asked

to indicate why they did not report their injury. They were given the choice of specific reasons

why they had not reported their injury (Appendix 2, Section D).

2.6.8 Dancers’ Attitudes and Perception of Injury

Dancers were asked to respond to nine attitudinal questions regarding injury. They were asked if

they considered themselves injured in relation to pain, functional changes, time-loss from work

and other possibilities (Appendix 2, Section C). After each statement, options available are:

strongly agree, agree, mildly agree, mildly disagree, disagree, and strongly disagree.

2.6.9 Contextual Company Information

This information was collected in the environmental scan in meetings with the artistic and

administrative staff of each participating company. The information that was collected common

to each company includes: number of dancers in the company, number of performances per year,

number of productions per year, if daily company class is required, if onsite treatment is

available, number of weeks of vacation per year, if the dancers are unionized, if the company

provides “sick classes” for injured dancers, and if the company dances on a raked stage.

2.7 Ethics

Ethical approval for the study protocol was obtained from the research ethics boards of:

University Health Network (Toronto, Canada), the University of Toronto (Toronto, Canada),

Lund University (Lund, Sweden), University of Southern Denmark (Odense, Sweden), and

Hadassah Hospital (Jerusalem, Israel). Ethics board approvals are located in Appendix 3.

23

2.8 Statistical Analysis

2.8.1 Data entry, double data entry, and data cleaning

Data was entered into SPSS 15.0 for Windows. Data cleaning was performed by manual

inspection and frequency analysis of variables. Outlying, unusual, or missing entries were

checked with the original questionnaires and corrected if necessary. Thirteen percent double data

entry was performed and an error rate was calculated using Statistical Analysis Software (SAS)

proc compare function.

2.8.2 Descriptive Statistics

Means with standard deviations and medians are used to describe the distribution of continuous

variables. I have additionally reported minimum and maximum scores for the NRS-11 to

describe the range of dance-related pain over the past week. Frequency and proportions in form

of percentages are reported for categorical data.

2.8.3 Prevalence of Dance-related MSK Injury

I have chosen to use two distinct outcomes to estimate the prevalence of dance-related MSK

injury:

Outcome 1: Self Reported Injury (SRI). To be reported as injured, the dancer had to choose that

they were injured, recovering from an injury, or suffering from a persistent injury.

Outcome 2: SEFIP score ≥3. In this analysis the dancer was defined as injured if they had a

SEFIP score ≥3 for any body region. This definition has a functional component (modifying

movement in order to dance).

To estimate self-reported injury prevalence, all non-dance related injuries were removed. The

options “injured”, “recovering from an injury”, and “suffering from a persistent injury” were

collapsed to form the numerator. The denominator for the self reported injury prevalence

estimate was the total number of dancers who responded to that specific question. This is

reported by dance company and style. I have reported 95% confidence intervals for the self-

reported injury point prevalence estimates.

24

To estimate SEFIP ≥3 injury prevalence, the number of distinct dancers with at least one body

region score of three or more was used for the numerator. The denominator was the total number

of dancers who responded to the SEFIP. This is reported by dance company and style. I have

reported 95% confidence intervals for the SEFIP ≥3 injury prevalence estimates.

2.8.4 Factors associated with MSK-injury in professional dancers

Logistic regression using Statistical Analysis Software 9.1 was performed to determine which

variables are associated with injury. Logistic regression is an appropriate statistical test when the

dependent variable is dichotomous as it is in this situation: “injured” or “not injured”.51, 52 Two

separate analyses were performed using the two different outcomes for “injury”. These are self-

reported injury and SEFIP score ≥3. The choice of variables to include in the analysis was

informed by the literature review. The independent variables analyzed are: sex, low body weight,

style of dance, low income, company, country, number of years dancing professionally, number

of years dancing total, age, number of years in present company, and rank (ballet only). The

continuous variables “number of years dancing total”, “number of years dancing professionally”,

“number of years dancing in the present company”, and “age” were highly skewed, therefore

quartiles were derived.

A preliminary univariate analysis was performed separately for ballet dancers and modern

dancers. Any variables with a p-value of less than 0.25 were then included in the multivariable

models. Backwards stepwise regression was then performed on these models and items with a p-

value greater than 0.10 were removed from the model. The strength of the association of each

variable with self reported injury and SEFIP score ≥3 is reported in the form of odds ratios with

95% confidence intervals.

CHAPTER 3: Results

3.1 Response rate Response rates by company are presented in Table 3.1. The response rates for ballet companies

were very similar with an overall response rate of 81%. The response rates for modern dance

companies ranged between 65 to 100% with an overall response rate of 82%. Two companies

had response rates lower than 80 percent. The reason for the lower response rates in the Kibbutz

Contemporary Dance Company and the Kibbutz Contemporary Dance Company 2 is most likely

due to difficult working conditions on the day the survey was scheduled. Survey distribution

took place after a technical run in a new studio without a proper ventilation system on a day of

extreme heat.

Table 3.1: Response rates Company # of participants # of dancers Response Rate (%)Ballet Companies: National Ballet of Canada 55 69 80 Royal Swedish Ballet 55 67 82 Royal Danish Ballet 68 83 82 Total Ballet Dancers 178 219 81 Modern Companies: Toronto Dance Theatre 14 16 88 Cullberg Ballet 16 20 80 Batsheva Dance Company 18 20 90 Ensemble Batsheva 15 15 100 Kibbutz Contemporary Dance Company 11 17 65 Kibbutz Contemporary Dance Company 2 8 12 67 Total Modern Dancers 82 100 82

25

26

3.2 Data entry error rate

The total number of discreet variables entered into the statistical software was 156 for 266 study

participants. A 13% double data entry was performed and 19 entry errors were identified. This

resulted in an error rate of 0.3%. These errors were corrected.

3.3 Sociodemographic characteristics of the study population

The sociodemographic characteristics of age, sex, marital status, and income are reported in

Table 3.2. Dancers in the Scandinavian companies (Royal Swedish Ballet, Royal Danish Ballet,

and Cullberg Ballet) are slightly older. The two junior companies (Ensemble Batsheva and

Kibbutz Contemporary Dance Company) are younger due to the nature of these companies.

There were more female participants than male participants in all three ballet companies.

Overall, 58% of ballet dancers were female. Male to female ratio of participants varied in the

modern dance companies and led to an overall equal percentage of male and female participants

when combined. Higher percentages of reported income below the low income cut-off were

reported in both Canadian companies (National Ballet of Canada and Toronto Dance Theatre) as

well as the Kibbutz Contemporary Dance Company 2.

The characteristics of body mass index and low body weight, as well as exposure to dance

(number of years dancing) are presented in Table 3.3. Mean body mass index is lowest in the

female National Ballet of Canada dancers; however, all three ballet companies had percentages

of females with low body weight approaching or greater than 50%. Scandinavian dancers (ballet

and modern) had the longest mean years dancing professionally and years dancing total.

Position or rank in the company was not reported in table format due to the differences in

ranking between companies. All ballet companies use a hierarchal ranking system consisting of

apprentice, corps de ballet, soloist and principal dancers. The Royal Swedish Ballet however,

does not have any apprentice dancers. Of the National Ballet of Canada participants, 7(12.7%)

were apprentices, 25(45.5%) were in the corps de ballet, and 23(41.8%) were soloists or

principal dancers. Of the Royal Swedish Ballet participants, 33(61.1%) were in the corps de

ballet and 21(38.9%) were soloist or principal dancers. Of the Royal Danish Ballet participants,

4(5.9%) were apprentices, 39(57.4%) were in the corps de ballet, and 25(36.8%) were soloist or

principal dancers. The Cullberg Ballet, the Batsheva Dance Company, and the Kibbutz

27

Contemporary Dance Company do not have any ranking system. The Toronto Dance Theatre

has full and junior company members as well as apprentices. Of the Toronto Dance Theatre

participants, 10(71.4%) were full company members, 2(14.3%) were junior company members

and 2(14.3%) were apprentices. The Batsheva Ensemble and the Kibbutz Contemporary Dance

Company 2 do not have a ranking system, but do have apprentices in the company. Of the

Batsheva Ensemble dancers, 1(6.7%) participant was an apprentice. Of the Kibbutz

Contemporary Dance Company 2 dancers, 1(12.5%) participant was an apprentice.

The percentage of dancers whose origin is from the country where the dance company is located

is reported in Table 3.4. The Cullberg Ballet had the lowest percentage of dancers from the

country where the company is located (31.3%) while the Kibbutz Contemporary Dance

Company 2 had the highest frequency (100.0%). In order not to identify specific dancers in each

company, the country of origin of all dancers is not broken down by company. Besides Canada,

Sweden, Denmark and Israel, dancers from the following countries participated in the study:

Armenia, Australia, Austria, Belarus, Belgium, Brazil, Bulgaria, China, England, Finland,

France, Germany, Hungary, Iceland, Italy, Japan, Lithuania, Mexico, New Zealand, Norway,

Philippines, Poland, Russia, Scotland, Serbia, South Africa, Spain, Switzerland, USA, and

Zambia.

Table 3.2: Sociodemographic characteristics of participating dancers: age, sex, marital status, and low-income cut-offs.

Ballet Companies

Modern Dance Companies

Demographic

NBC n=55

RSB n=55

RDB n=68

TDT n=14

CUL n=16

BAT n=18

ENS n=15

KDC n=11

KDC2 n=8

Age in years mean(SD),med

26(5.4),25

30(6.3),30

27(6.1),26

26(4.8),26

30(4.7),30

27(3.4),27

22(2.1),23

25(4.2),25

21(0.8),21

Sex: n(%) Female

29(52.7)

35(64.8)

40(58.8)

6(42.9)

8(50.0)

9(50.0)

7(46.7)

8(72.7)

3(37.5)

Marital status: n(%) Never married Married Common law Divorced Widowed

31(56.4)

12(21.8) 6(10.9)

5(9.1) 1(1.8)

22(41.5)

14(26.4) 16(30.2)

1(1.9)

0

48(77.4)

10(16.1) 3(4.8)

1(1.5)

0

13(92.9) 0

1(7.1) 0 0

12(75.0)

2(12.5) 2(12.5)

0 0

11(61.1)

1(5.6) 5(27.8)

1(5.6)

0

14(93.3)

1(6.7) 0 0 0

11(100) 0 0 0 0

8(100) 0 0 0 0

Income below low income cut-off*: n(%)

8(14.5)

2(4.0)

1(1.5)

7(50.0)

0

0

1(6.7)

0

8(100.0)

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva; KDC, Kibbutz Contemporary Dance Company; KDC2, Kibbutz Contemporary Dance Company 2; SD, Standard deviation; Med, Median;BMI, Body Mass Index. *Low income cut-offs: Canada, <20,778 Canadian Dollars/year; Sweden, <140,400 Swedish Krona/year; Denmark, <100,000 Danish Krone/year; Israel, <3,710 Israeli New Shekel/month.

28

29

Ballet Companies

Modern Dance Companies

NBC n=55

RSB n=55

RDB n=68

TDT n=14

CUL n=16

BAT n=18

ENS n=15

KDC n=11

KDC2 n=8

BMI: males mean(SD), med

22.2(1.2),

22.4

22.5(1.6),

22.5

22.2(1.3),

21.8

22.2(1.1),

22.2

22.4(1.7),

22.0

22.2(2.2),

21.8

20.5(2.0),

20.6

20.6(1.0),

21.1

22.2(2.5),

20.9 BMI: females mean(SD), med

18.2(0.9),

18.1

18.7(1.1),

18.6

18.5(0.9),

18.4

21.3(2.0),

21.2

20.7(1.4),

20.8

20.4(1.3),

20.1

20.1(1.9),

19.7

19.7(0.9),

19.4

20.2(0.6),

20.3 Low body weight males*: n(% of males)

0

0

0

0

0

0

1(12.5)

0

0

Low body weight females*: n(% of females)

21(72.4)

17(48.6)

19(47.5)

0

0

0

1(14.3)

1(12.5)

0

Exposure: mean(SD),med Years in company

6.7(5.4),5.0

9.2(7.0),7.5

8.8(6.0),7.0

4.8(3.4).3.5

4.6(5.2),2.5

7.0(2.3).7.0

1.9(0.9),2.0

4.2(3.5),3.0

1.3(0.5),1.0

Years dancing professionally

8.1(5.8),7.0

12.4(6.7),

13.0

9.7(6.4),8.0

5.3(4.0).4.0

11.2(6.1),

9.5

8.6(2.8),9.0

3.2(1.7),3.0

5.7(3.1),5.0

2.1(1.5),1.5

Years dancing total

16.0(5.7),

15.0

20.7(6.8),

20.5

17.3(7.3),

16.0

13.4(6.4),

12.0

19.0(6.1),

18.5

15.7(5.2),

15.0

9.5(5.0),8.0

15.2(6.1),

15.0

7.6(2.9),7.5

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva; KDC, Kibbutz Contemporary Dance Company; KDC2, Kibbutz Contemporary Dance Company 2; SD, Standard deviation; BMI, Body Mass Index. Low body weight defined as BMI <18.5.

Table 3.3: Characteristics of participating dancers: Body Mass Index, low body weight, and years dancing.

30

Table 3.4 Country of Origin Company Name (Country) Dancers Originating from Country of

Dance Company n(%)

National Ballet of Canada (Canada)

30(54.5)

Royal Swedish Ballet (Sweden)

27(50.0)

Royal Danish Ballet (Denmark)

37(54.4)

Toronto Dance Theatre (Canada)

11(78.6)

Cullberg Ballet (Sweden)

5(31.3)

Batsheva Dance Company (Israel)

12(66.7)

Ensemble Batsheva (Israel)

10(66.7)

Kibbutz Contemporary Dance Company (Israel)

8(72.7)

Kibbutz Contemporary Dance Company 2 (Israel)

8(100.0)

3.4 Self Estimated Functional Inability because of Pain (SEFIP) scores

Dancers with SEFIP scores ≥3 are reported in Table 3.5. I have chosen to report

percentages of scores of 3 or greater, as a score of 3 denotes some degree of functional

impairment (“Much pain, must avoid some movements”). Thus, the SEFIP scores can

provide a snapshot of the companies’ musculoskeletal health regarding both pain and

function for each body region.

Ballet companies’ SEFIP scores followed similar patterns (Table 3.5). When companies

were combined, ballet dancers reported highest percentage of SEFIP scores ≥3 for ankles

and feet followed by low back, hips, and knees (Table 3.6). This pattern was similar for

both males and females. Slight differences did exist between ballet companies for body

areas outside of these four most frequent reported problematic regions. The National

Ballet of Canada had a higher frequency of SEFIP scores ≥3 for the calf region (5.5%)

31

compared to the Royal Swedish Ballet (1.8%) and the Royal Danish Ballet (0). The

National Ballet of Canada had no reported SEFIP scores ≥3 for the mid-back region

compared to the Royal Swedish Ballet (3.6%) and the Royal Danish Ballet (6.9%). The

posterior thigh region differed between males (1.4%) and females (4.9%) with the

majority of these scores occurring in the Royal Swedish Ballet with 9.1% of the dancers

having SEFIP scores ≥3 for the posterior thigh region. Overall, the frequency of SEFIP

scores ≥3 for the upper limb in ballet dancers was very low. Only the dancers in the RDB

reported any SEFIP scores ≥3 for the shoulder (2.7%) and the wrist hand regions (1.4%).

No ballet dancers reported SEFIP scores ≥3 for the elbows or the anterior thigh regions.

In contrast to ballet dancers, modern dancers’ body region with the highest percentage of

SEFIP scores ≥3 varied between modern dance companies (Table 3.5). The shoulder

region was highest for the Toronto Dance Theatre dancers (21.4%). The low back region

was highest for the Cullberg Ballet (25.1%), Kibbutz Contemporary Dance Company

(27.3%) and Kibbutz Contemporary Dance Company 2(37.5%) dancers. Toes were

equally as problematic for the Kibbutz Contemporary Dance Company 2 dancers. The

neck was the most problematic region for the Batsheva Dance Company dancers (22.3%).

The Ensemble Batsheva dancers had equal problems with low back, hips, shoulders,

wrist/hand, and ankles/feet (6.7%). No male modern dancers reported SEFIP scores ≥3

for the neck compared to 12.2% of females (Table 3.6). Male modern dancers did report

SEFIP scores ≥3 for the wrist/hand (4.9%) and the shin (4.9%) regions while no females

reported SEFIP scores ≥3 in these regions. No modern dancers reported SEFIP scores ≥3

for the anterior thigh or calf regions.

Table 3.5: Frequency of SEFIP scores ≥ 3 (by company) Location

NBC n=55 n(%)

RSB n=55 n(%)

RDB n=68 n(%)

TDT n=14 n(%)

CUL n=16 n(%)

BAT n=18 n(%)

ENS n=15 n(%)

KDC n=11 n(%)

KDC2 n=8 n(%)

Neck

1(1.8) 1(1.8) 0 1(7.1) 0 4(22.3) 0 0 0

Mid-Back

0 2(3.6) 5(6.9) 1(7.1) 1(6.3) 0 0 1(9.1) 1(12.5)

Elbows

0 0 0 1(7.1) 0 0 0 0 0

Lower Back

3(5.5) 5(9.1) 8(11.0) 1(7.1) 4(25.1) 2(11.2) 1(6.7) 3(27.3) 3(37.5)

Hips

5(9.1) 5(9.1) 3(4.4) 0 1(6.3) 3(16.7) 1(6.7) 1(9.1) 0

Posterior Thighs

0 5(9.1) 1(1.4) 0 0 0 0 1(9.1) 0

Shoulders

0 0 2(2.7) 3(21.4) 0 1(5.6) 1(6.7) 0 0

Wrists/hands

0 0 1(1.4) 0 0 1(5.6) 1(6.7) 0 0

Anterior Thighs

0 0 0 0 0 0 0 0 0

Knees

3(5.5) 6(10.9) 4(5.9) 0 2(12.5) 0 0 1(9.1) 0

Shins

1(1.8) 0 0 0 0 0 0 0 2(25.0)

Calves

3(5.5) 1(1.8) 0 0 0 0 0 0 0

Ankles/feet

9(16.4) 11(20.0) 8(11.0) 1(7.1) 1(6.3) 3(16.7) 1(6.7) 1(9.1) 0

Toes 2(3.6) 2(3.6) 1(1.4) 0 1(6.3) 1(5.6) 0 1(9.1) 3(37.5) Abbreviations: SEFIP, Self Estimated Functional Inability because of Pain; NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva; KDC, Kibbutz Contemporary Dance Company; KDC2, Kibbutz Contemporary Dance Company 2.

32

33

Table 3.6: Frequency of SEFIP scores ≥ 3 (by style, sex)

Ballet

Modern

Location Male n=73 n(%)

Female n=103 n(%)

Male n=41 n(%)

Female n=41 n(%)

Neck

1(1.4) 1(1.0) 0 5(12.2)

Mid-Back

2(2.8) 5(4.9) 3(7.3) 1(2.4)

Elbows

0 0 0 1(2.4)

Lower Back

6(8.2) 9(8.7) 5(12.2) 6(14.6)

Hips

4(5.5) 7(6.8) 3(7.3) 3(7.3)

Posterior Thighs

1(1.4) 5(4.9) 0 1(2.4)

Shoulders

1(1.4) 0 3(7.3) 2(4.9)

Wrists/hands

0 1(1.0) 2(4.9) 0

Anterior Thighs

0 0 0 0

Knees

4(5.5) 4(4.0) 1(2.4) 2(4.9)

Shins

0 1(1.0) 2(4.9) 0

Calves

1(1.4) 3(2.9) 0 0

Ankles/feet

11(15.1) 17(16.3) 4(9.8) 3(7.3)

Toes 1(1.4) 4(3.9) 3(7.3) 3(7.3) Abbreviations: SEFIP, Self Estimated Functional Inability because of Pain

34

3.5 Numeric Rating Scale Scores: Dance related pain over the last week.

Descriptive results of the NRS-11 scores of dance related pain over the last week are

presented in Table 3.7. Mean scores for ballet and modern dancers were similar, with

ballet dancers reporting a mean score of 4.3 (2.3 SD) average pain over the last week and

modern dancers reporting a mean score of 4.5 (2.0 SD) average pain over the last week.

Dancers reported scores at all levels of the scale including both extremes of 0 (no pain) as

well as 10 (worst possible pain). Overall, the majority of dancers are reporting some

degree of pain. The frequency of pain by cut-points along the NRS-11 scale is presented

in Table 3.8. Higher frequencies of ballet dancers are reporting scores of “no pain” than

modern dancers; however, no modern dancers reported NRS-11 scores higher than 8.

Ballet dancers in two companies reported scores of “worst possible pain” (Table 3.7).

Overall, the majority of dancers are reporting pain in the range of 1-4 (mild) followed by

5-7 (moderate), 8-10 (severe), and “no pain” ranges respectively. Two exceptions

occurred in the Toronto Dance Theatre and the Kibbutz Contemporary Dance Company

where dancers reported higher frequencies of pain in the 5-7 range (moderate) followed

by the 1-4 (mild), 8-10 (severe), and “no pain” ranges respectively.

35

Table 3.7: Average dance-related pain over last week, Numeric Rating Scale-11 scores

Mean Median SD Minimum-Maximum Ballet dancers(n=176)

4.3 4.0 2.3 0-10

National Ballet of Canada(n=55) 4.7 5.0 2.0 0-10 Royal Swedish Ballet(n=55) 4.3 3.0 2.6 0-9 Royal Danish Ballet(n=67) 3.9 3.0 2.3 0-10

Modern dancers(n=82)

4.5 5.0 2.0 0-8

Toronto Dance Theatre(n=14) 5.1 5.0 1.9 1-8 Cullberg Ballet(n=16) 3.8 3.0 2.0 1-8 Batsheva Dance Company(n=18) 4.0 3.5 2.0 1-8 Ensemble Batsheva (n=15) 4.3 4.0 1.8 2-7 Kibbutz Contemporary Dance Company(n=11)

5.0 6.0 2.3 0-8

Kibbutz Contemporary Dance Company 2 (n=8)

6.0 6.0 1.4 4-8

Abbreviations: SD, Standard deviation.

36

Table 3.8: Pain severity using Numeric Rating Scale-11 cut-points. Average dance-related pain over last week.

NRS-11 score: {0} {1-4} {5-7} {8-10} n(%) n(%) n(%) n(%) Ballet dancers (n=176) 8(4.5) 93(52.9) 61(34.7) 14(7.9) National Ballet of Canada (n=55) 1(1.8) 25(45.4) 25(45.4) 4(7.3) Royal Swedish Ballet (n=55) 4(7.3) 26(38.3) 19(34.5) 6(10.9) Royal Danish Ballet (n=67) 4(6.0) 42(62.8) 17(25.4) 4(6.0) Modern dancers (n=82) 1(1.2) 39(47.6) 37(45.1) 5(6.1) Toronto Dance Theatre (n=14) 0 5(35.6) 8(57.1) 1(7.1) Cullberg Ballet (n=16) 0 11(68.9) 4(25.1) 1(6.3) Batsheva Dance Company (n=18) 0 11(61.1) 6(33.4) 1(5.6) Ensemble Batsheva (n=15) 0 9(60.0) 6(40.0) 0 Kibbutz Contemporary Dance Company (n=11) 1(9.1) 2(18.2) 7(63.7) 1(9.1) Kibbutz Contemporary Dance Company 2 (n=8) 0 1(12.5) 6(75.0) 1(12.5) Abbreviations: NRS, Numeric Rating Scale. Categories based on cut points50: {0}= no pain, {1-4}= mild, {5-7}= moderate, {8-10}= severe

37

3.6 Current treatment The majority of dancers reported they were currently receiving treatment for dance-

related pain (Table 3.9). Dancers in the TDT were the only group in which less than 50%

of dancers reported currently receiving treatment for their dance-related pain. The types

of healthcare practitioners that these dancers were receiving care from are reported in

Table 3.10 and in aggregate format by style in Table 3.11. Some types of healthcare

utilized by dancers are country dependent. Naprapaths were utilized only by Swedish

dancers. Osteopaths were utilized by Swedish and Danish dancers. Athletic therapists

were utilized by Canadian and Swedish ballet dancers. Israeli dancers did not utilize

chiropractic care. The majority of ballet and modern dancers receiving treatment are

utilizing massage therapy and physiotherapy followed by acupuncture. Very few ballet

dancers and no modern dancers were receiving treatment from a medical doctor for

dance-related pain. Where dancers are receiving treatment is detailed in Table 3.12.

Modern dancers are more likely to solely receive care off-site than ballet dancers with the

exception of the KDC and KDC2 dancers.

38

Table 3.9: Dancers currently receiving treatment for dance-related pain.

Dancers Currently Receiving Treatment

n(%)

Ballet dancers (n=177)

108(61.0)

National Ballet of Canada (n=55) 33(60.0) Royal Swedish Ballet (n=55) 35(63.6) Royal Danish Ballet (n=68) 40(58.8) Modern dancers (n=82)

60(73.2)

Toronto Dance Theatre (n=14) 6(42.9) Cullberg Ballet (n=16) 9(56.3) Batsheva Dance Company (n=18) 16(88.9) Ensemble Batsheva (n=15) 10(66.7) Kibbutz Contemporary Dance Company (n=11)

11(100.0)

Kibbutz Contemporary Dance Company 2 (n=8)

8(100.0)

39

NBC N=33 n(%)

RSB N=35 n(%)

RDB N=40 n(%)

TDT N=6 n(%)

CUL N=9 n(%)

BAT N=16 n(%)

ENS N=10 n(%)

KDC N=11 n(%)

KDC2 N=8 n(%)

Acupuncturist

4(12.1) 9(25.7) 6(15.0) 2(33.3) 1(11.1) 9(56.3) 4(40.0) 5(45.5) 2(25.0)

Athletic Therapist

17(51.5) 2(5.7) 0 0 0 0 0 0 0

Chiropractor

2(6.1) 7(20.0) 2(5.0) 2(33.3) 1(11.1) 0 0 0 0

Massage Therapist

29(87.9) 15(42.9) 25(62.5) 4(66.7) 5(55.6) 6(37.5) 7(70.0) 11(100.0) 7(87.5)

Medical Doctor

3(9.1) 3(8.6) 5(12.5) 0 0 0 0 0 0

Medical Specialist

0 1(2.9) 1(2.5) 0 0 0 0 0 0

Naturopath

2(6.1) 1(2.9) 1(2.5) 1(16.7) 1(11.1) 0 0 0 0

Naprapath

n/a 10(28.6) n/a n/a 1(11.1) n/a n/a n/a n/a

Osteopath

2(5.7) 7(17.5) 0 6(66.7) 0 0 0 0

Physiotherapist

24(72.7) 15(42.9) 28(70.0) 2(33.3) 2(22.2) 12(75.0) 9(90.0) 9(81.8) 7(87.5)

Psychologist/ Psychiatrist/ Counselor

2(6.1) 0 4(10.0) 1(16.7) 2(22.2) 1(6.3) 1(10.0) 0 0

Other 3(9.4) 0 4(10.0) 2(33.3) 1(11.1) 7(43.8) 2(20.0) 1(9.1) 0 Includes only dancers who responded that they were receiving treatment for dance-related pain. Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva; KDC, Kibbutz Contemporary Dance Company; KDC2, Kibbutz Contemporary Dance Company 2; n/a, not applicable.

Table 3.10: Treatment from Healthcare Practitioners (only dancers currently receiving treatment)

40 Table 3.11: Frequency of Treatment from Healthcare Practitioners (only dancers currently receiving treatment)

Ballet N=108 n(%)

Modern N=60 n(%)

Acupuncturist

19(17.4) 23(38.3)

Athletic Therapist

19(17.4) 0

Chiropractor

11(10.1) 3(5.0)

Massage Therapist

69(63.3) 40(66.7)

Medical Doctor

11(10.1) 0

Medical Specialist

2(1.8) 0

Naturopath

4(3.7) 2(3.3)

Naprapath

10(9.2) 1(1.7)

Osteopath

16(14.7) 6(10.0)

Physiotherapist

68(62.4) 41(68.3)

Psychologist/ Psychiatrist/ Counselor

6(5.5) 5(8.3)

Other 7(6.5) 13(21.7)Includes only dancers who responded that they were receiving treatment for dance-related pain.

41

Table 3.12: Site of Current Treatment (only dancers currently receiving treatment)

On-site n(%)

Off-site n(%)

Both n(%)

Ballet (N=107)

49(45.8) 11(10.3) 47(43.9)

National Ballet of Canada (N=34) 11(32.4) 4(11.8) 19(55.9) Royal Swedish Ballet (N=34) 18(52.9) 6(17.6) 10(29.4) Royal Danish Ballet (N=39) 20(51.3) 1(2.6) 18(46.2) Modern (N=59)

19(32.2) 33(55.9) 7(11.9)

Toronto Dance Theatre (N=6) 0 6(100.0) 0 Cullberg Ballet (N=8) 0 7(87.5) 1(12.5) Batsheva Dance Company (N=16) 2(12.5) 10(62.5) 4(25.0) Ensemble Batsheva (N=10) 0 9(90.0) 1(10.0) Kibbutz Contemporary Dance Company (N=11) 9(81.8) 1(9.1) 1(9.1) Kibbutz Contemporary Dance Company 2 (N=8) 8(100.0) 0 0 Includes only dancers who responded that they were receiving treatment for dance-related pain.

42

3.7 Pain Medication Use

Frequency of pain medication use is reported in Table 3.13. Canadian ballet (58.2%) and modern

(50.0%) dancers report higher use of non-prescription pain medications in the past week

compared to other countries. Amongst ballet dancers, the Canadian dancers (20.0%) also

reported the highest frequency of prescription pain medication use. There was one reported use

of prescription pain medication use in modern dancers.

Table 3.13: Pain medication use in last week (all dancers)

Non-prescription pain medication use in last week

n(%)

Prescription pain

medication use in last week n(%)

Ballet dancers (N=175)

69(39.4) 25(14.3)

National Ballet of Canada (n=55)

32(58.2) 11(20.0)

Royal Swedish Ballet (n=53) 20(37.7) 10(18.5) Royal Danish Ballet (n=67) 17(25.4) 4(6.0) Modern dancers (n=82)

18(22.0) 1(1.2)

Toronto Dance Theatre (n=14)

7(50.0) 0

Cullberg Ballet (n=16) 4(25.0) 0 Batsheva Dance Company (n=18)

4(22.2) 0

Ensemble Batsheva (n=15) 0 0 Kibbutz Contemporary Dance Company (n=11)

1(9.1) 1(9.1)

Kibbutz Contemporary Dance Company 2 (n=8)

2(25.0) 0

43

3.8 Injury Prevalence Dancers’ current self-reported injury status is detailed in Table 3.14. Almost ¼ of all dancers are

reporting a persistent injury. Four dancers reported injuries that were not dance-related and have

been removed. The point prevalence of self-reported injury (Outcome 1) is reported with 95%

confidence intervals in Table 3.15. (Non-dance related injuries have been removed from this

table). The aggregate point prevalence of self-reported injury (SRI) for ballet dancers was 54.8%.

This ranged from 47.1% in the Royal Danish Ballet to 59.3% in the Royal Swedish Ballet. The

aggregate point prevalence of SRI for modern dancers is 46.3%. This ranged from 9.1% in the

Kibbutz Contemporary Dance Company to 66.7% in the Batsheva Dance Company.

The point prevalence of SEFIP ≥3 injury (Outcome 2) is reported with 95% confidence intervals

in Table 3.16. The aggregate point prevalence of SEFIP ≥3 injury in ballet dancers is 38.8%.

This ranged from 33.8% in the Royal Danish Ballet to 47.3% in the Royal Swedish Ballet. The

aggregate point prevalence of SEFIP ≥3 injury in modern dancers is 45.1%. This ranged from

20.0% in the Ensemble Batsheva to 100.0% in the Kibbutz Contemporary Dance Company 2.

44 Table 3.14: Current Injury Status

Injured

n(%)

Recovering from an Injury n(%)

Persistent Injury n(%)

Not Injured n(%)

Ballet Dancers (n=177)

17(9.6) 38(21.5) 44(24.9) 78(44.1)

National Ballet of Canada (n=55) 4(7.3) 15(27.3) 13(23.6) 23(41.8) Royal Swedish Ballet (n=54) 7(13.0) 8(14.8) 19(35.2) 20(37.0) Royal Danish Ballet (n=68) 6(8.8) 15(22.1) 12(17.6) 35(51.5) Modern Dancers (n=82)

9(11.0) 11(13.4) 19(23.2) 43(52.4)

Toronto Dance Theatre (n=14) 2(14.3) 0 5(35.7) 7(50.0) Cullberg Ballet (n=16) 2(12.5) 2(12.5) 3(18.8) 9(56.3) Batsheva Dance Company (n=18) 2(11.1) 6(33.3) 4(22.2) 6(33.3) Ensemble Batsheva (n=15) 2(13.3) 3(20.0) 4(26.7) 6(40.0) Kibbutz Contemporary Dance Company (n=11)

0 0 1(9.1) 10(91.9)

Kibbutz Contemporary Dance Company 2 (n=8)

1(12.5) 0 2(25.0) 5(62.5)

45 Table 3.15: Point prevalence of Self Reported Injury

Prevalence of Dance-related MSK Injury %(95%CI)

Ballet dancers (n=177)

54.8 (47.7 – 62.1)

National Ballet of Canada (n=55) 58.2 (45.1 – 71.2) Royal Swedish Ballet (n=54) 59.3 (46.1 – 72.4) Royal Danish Ballet (n=68) 47.1 (35.2 - 58.9) Modern dancers (n=82)

46.3 (35.5 – 57.1)

Toronto Dance Theatre (n=14) 42.9 (16.9 – 68.8) Cullberg Ballet (n=16) 43.7 (19.4 – 68.1) Batsheva Dance Company (n=18) 66.7 (44.9 – 88.4) Ensemble Batsheva (n=15) 60 (35.2 – 84.8) Kibbutz Contemporary Dance Company (n=11)

9.1 (0– 26.1)

Kibbutz Contemporary Dance Company 2 (n=8)

37.5 (3.9 – 71.0)

Table 3.16: Point prevalence of SEFIP≥3 Injury Prevalence of SEFIP≥3 Injury

%(95%CI)

Ballet dancers (n=178)

38.8 (30.9 – 45.1)

National Ballet of Canada (n=55) 36.4 (23.3 – 48.7) Royal Swedish Ballet (n=55) 47.3 (33.8 – 60.2) Royal Danish Ballet (n=68) 33.8 (22.7 – 45.3) Modern dancers (n=82)

45.1 (34.2 – 55.8)

Toronto Dance Theatre (n=14) 35.7 (10.9 – 61.1) Cullberg Ballet (n=16) 31.3 (8.3 – 53.7) Batsheva Dance Company (n=18) 55.6 (33.1 – 78.9) Ensemble Batsheva (n=15) 20.0 (0 – 40.2) Kibbutz Contemporary Dance Company (n=11) 54.5 (25.6– 84.4) Kibbutz Contemporary Dance Company 2 (n=8) 100.0 (100.0 – 100.0)

Abbreviations: SEFIP, Self Estimated Functional Inability because of Pain

46

3.9 Factors associated with self-reported dance-related musculoskeletal injuries (SRI) in dancers.

3.9.1 Univariate analysis (crude analysis)

The results of the univariate analysis for ballet dancers are reported in Table 3.17. The frequency

of injury for each variable considered for the multivariable analysis is reported with associated

odds ratios and 95% confidence intervals. The variables that have met the criteria to be included

in the regression analysis are sex, low body weight, low income, rank, number of years dancing

total, number of years dancing professionally, number of years dancing in present company, and

age. The univariate analyses suggest that females are less likely to report injury than males;

dancers with low body weight are less likely to report injury than dancers with normal body

weight; dancers earning below the low income threshold are less likely to report injury than

dancers above the threshold. Soloist or principal dancers are more likely to report an injury than

corps de ballet dancers whereas apprentices are less likely. Dancers in the three quartiles above

22 years of age were more likely to report an injury than younger dancers in the reference age

group of ≤22 years. Dancers dancing more than three years professionally (all three quartiles)

were more likely to report injury than the reference group of dancers dancing three or fewer

years professionally. Dancers who reported dancing 17-23 years total and ≥24 years total were

more likely to report an injury than dancers who danced ≤11 years total. Dancers who had

danced 7-12 years or ≥13 years in the present company are more likely to report an injury than

those dancers who had danced ≤2 years in the present company. The variables company and

country were not significantly associated with self-reported injury.

The univariate analysis for modern dancers is presented in Table 3.18. The Kibbutz

Contemporary Dance Company dancers were less likely to report an injury than the Toronto

Dance Theatre dancers (OR = 0.10). The variables sex, low body weight, low income, country,

number of years dancing total, number of years dancing professionally, number of years in

present company, and age were not significantly associated with self-reported injury in the

univariate analysis. Due to the fact that no other variables met the criteria for inclusion in the

regression analysis, multivariable analysis was not performed for modern dancers.

47

Table 3.17: Univariate Analysis Results for Self Reported Injury(ballet dancers only) Variable Not injured

n(%) Injured n(%)

OR 95% CI p-value

Sex: Female

52(66.7)

52(52.5)

0.55

0.30 – 1.02

0.06

Age ≤22 years 23-26 years 27-32 years ≥33 years

26(33.3) 20(25.6) 15(19.2) 17(21.8)

16(16.3)25(25.5)27(27.6)30(30.6)

1.00 2.03 2.93 2.87

0.86 – 4.781.21 – 7.101.21 – 6.79

0.10 0.02 0.02

Low body weight (<18.5 BMI)

31(40.3)

26(27.7)

0.57 0.30 – 1.08 0.08

Low income: Below cut-off

9(11.5)

2(2.1)

0.16

0.03 – 0.77

0.02

Rank: Corps Apprentice Soloist/principal

49(62.8) 8(10.3) 21(26.9)

48(48.5)3(3.0)

48(48.5)

1.00 0.38 2.33

0.10 – 1.531.22 – 4.47

0.17 0.01

Number of years dancing total ≤11 years 12-16 years 17-23 years ≥24 years

22(28.6) 21(27.3) 18(23.4) 16(20.8)

16(16.5)22(22.7)30(30.9)29(29.9)

1.00 1.44 2.29 2.49

0.60 – 3.470.96 – 5.471.03 – 6.05

0.42 0.06 0.04

Number of years dancing professionally ≤3 years 4-8 years 9-15.4 years ≥15.5 years

23(29.5) 20(25.6) 17(21.8) 18(23.1)

12(12.2)28(28.6)32(32.7)26(26.5)

1.00 2.68 3.61 3.04

1.09 – 6.621.45 – 8.991.10 – 6.95

0.03 0.006 0.01

Number of years in present company ≤2 years 3-6 years 7-12 years ≥13 years

22(28.2) 23(29.5) 14(18.0) 19(24.4)

17(17.4)23(23.5)30(30.6)28(28.6)

1.00 1.29 2.77 1.91

0.55 – 3.051.13 – 6.790.81 – 4.51

0.56 0.03 0.03

Company: National Ballet of Canada Royal Swedish Ballet Royal Danish Ballet

23(41.8) 20(37.0) 35(51.5)

32(58.2)34(63.0)33(48.5)

1.00 1.22 0.68

0.57 – 2.640.33 – 1.39

0.61 0.28

48 Table 3.17: Univariate Analysis Results for Self Reported Injury(ballet dancers only) Variable Not injured

n(%) Injured n(%)

OR 95% CI p-value

Country: Canada Sweden Denmark *

23(29.5) 20(25.6) 35(44.9)

32(32.3)34(34.3)33(33.3)

1.00 1.22 0.68

0.57 – 2.640.33 – 1.39

0.61 0.29

Abbreviations: OR, odds ratio; CI, confidence interval, BMI, body mass index. *Israel not included as there were no participating ballet companies in Israel.

49

Table 3.18: Univariate Analysis Results for Self Reported Injury (modern dancers only)

Variable Not injured

n(%) Injured n(%)

OR 95% CI p-value

Sex: Female

22(51.2)

19(48.7)

0.91

0.38 – 2.16

0.83

Age ≤21 years 22-24 years 25-27 years ≥28 years

12(29.3) 6(14.6) 10(24.4) 13(31.7)

7(18.0) 10(25.6)13(33.3)9(23.1)

1.00 2.86 2.23 1.19

0.72 – 11.310.64 – 7.74 0.34 – 4.19

0.13 0.21 0.79

Low body weight (<18.5 BMI)

2(4.9)

1(2.6)

0.51

0.05 – 5.90

0.59

Low income: Below cut-off

9(20.9)

7(18.0)

0.16

0.28 – 2.48

0.73

Number of years dancing total ≤8 years 9-12 years 13-18 years ≥19 years

11(26.2) 10(23.8) 9(21.4) 12(28.6)

9(23.1) 10(25.6)10(25.6)10(25.6)

1.00 1.22 1.36 1.02

0.35 – 4.24 0.39 – 4.79 0.30 – 4.24

0.75 0.63 0.98

Number of years dancing professionally ≤2 years 3-4 years 5-8 years ≥9 years

8(19.1) 10(23.8) 11(26.2) 13(31.0)

10(25.6)4(10.3) 13(33.3)12(30.8)

1.00 0.32 0.95 0.74

0.07 – 1.42 0.28 – 3.23 0.22 – 2.49

0.13 0.93 0.63

Number of years in present company ≤2 years 3-6 years ≥7 years

19(44.2) 12(27.9) 12(27.9)

18(46.2)11(28.2)10(25.6)

1.00 0.97 0.88

0.34 – 2.74 0.31 – 2.54

0.95 0.81

Company: Toronto Dance Theatre Cullberg Ballet Batsheva Dance Company Ensemble Batsheva Kibbutz Dance Company Kibbutz Dance Company 2

7(50.0) 9(56.3) 6(33.3) 6(40.0) 10(90.9) 5(62.5)

7(50.0) 7(43.8) 12(66.7)9(60.0) 1(9.1) 3(37.5)

1.00 0.78 2.00 1.50 0.10 0.60

0.18 – 3.28 0.48 – 8.40 0.34 – 6.54 0.01 – 1.01 0.10 – 3.53

0.73 0.34 0.59 0.05 0.57

50 Table 3.18: Univariate Analysis Results for Self Reported Injury (modern dancers only)

Variable Not injured

n(%) Injured n(%)

OR 95% CI p-value

Country: Canada Sweden Israel *

7(16.3) 9(20.9) 27(62.8)

7(18.0) 7(18.0) 25(64.1)

1.00 0.78 0.93

0.18 – 3.28 0.28 – 3.02

0.73 0.90

Abbreviations: OR, odds ratio; CI, confidence interval, BMI, body mass index. *Denmark not included as there were no participating modern companies in Denmark.

3.9.2 Multivariable analysis (logistic regression)

The model for the multivariable analysis for ballet dancers was created based on the results of

the univariate analysis. Spearman’s correlational coefficient was used to determine correlation

between the continuous variables. Years dancing professionally, years dancing total, years

dancing in present company, and age were all highly correlated with each other (ρ > 0.80). I

have chosen to include only years dancing professionally in the multivariable model. This

variable best represents the professional dancers’ exposure to dance at the elite professional level

and most likely has less variability in the exposure than years dancing total.

The variables included in the multivariable analysis are:

sex, low body weight, years dancing professionally, low income, and rank.

The results of the logistic regression analysis for ballet dancers are reported in Table 3.19. The

variables low body weight, years dancing professionally, and low income were all removed from

the model via backwards stepwise regression. Soloist and principal dancers were more likely to

report an injury than dancers in the corps de ballet (OR = 2.44). Female dancers were less likely

to report an injury than male dancers, but the results are not statistically significant.

51 Table 3.19: Final Model for Logistic Regression Analysis. Factors Associated with Self Reported Injury (ballet dancers only) Variable β OR 95% CI p-value Sex (female) Rank: Corps de ballet Apprentice Soloist/principal Intercept

-0.55

-0.87 0.89 0.23

0.58

1.00 0.42 2.44

0.30 – 1.11

0.10 – 1.69 1.25 – 4.78

0.07

0.22 0.009

Abbreviations: β, beta; OR, odds ratio; CI, confidence interval, BMI, body mass index.

3.10 Factors associated with SEFIP score of ≥3.

3.10.1 Univariate analysis (crude analysis)

The results of the univariate analysis for ballet dancers are reported in Table 3.20. The frequency

of injury for each variable considered for the multivariable analysis is reported with associated

odds ratios and 95% confidence intervals. The variables that have met the criteria to be included

in the regression analysis are low income, rank, number of years dancing total, number of years

dancing professionally, number of years dancing in the present company, and age. The

univariate analyses suggest that ballet dancers earning below the low income threshold are less

likely to report injury than dancers above the threshold. Soloist or principal dancers are more

likely to report a SEFIP score ≥3 than corps de ballet dancers whereas apprentices are less likely

to report a SEFIP score ≥3. Dancers in the three quartiles above 22 years of age were more likely

to report a SEFIP score ≥3 than younger dancers in the reference age group of ≤22 years.

Additionally, dancers dancing 9-15.4 years professionally as well as ≥15.5 years professionally

were more likely to report a SEFIP score ≥3 than the reference group of dancers dancing three or

fewer years professionally. Dancers who reported dancing 17-23 years total and ≥24 years total

were more likely to report a SEFIP score ≥3 than dancers who danced ≤11 years total. Dancers

who had danced 7-12 years or ≥13 years in the present company are more likely to report a

SEFIP score ≥3 than those dancers who had danced ≤2 years in the present company. The

variables sex, low body weight, company, and country were not significantly associated with a

SEFIP score ≥3.

52

The univariate analysis for modern dancers is presented in Table 3.21. The variables that have

met the criteria to be included in the regression analysis are low income, age, and number of

years dancing professionally. The univariate analyses suggest that modern dancers with low

income are more likely to report a SEFIP score ≥3 than dancers above the low income threshold.

Modern dancers between 22-24 years of age are less likely to report a SEFIP score ≥3 than

dancers less than 21 years of age; dancers dancing more than 3-4 years professionally are less

likely to report a SEFIP score ≥3 than dancers dancing two years or less professionally. The

variables sex, low body weight, number of years dancing total, number of years dancing in

present company, and country were not significantly associated with injury. Due to the small

sample sizes of each individual modern dance company, the company variable could not be

analyzed as the validity of the model fit was questionable for this variable.

53 Table 3.20: Univariate Analysis for SEFIP score of ≥3 (ballet dancers only)

Variable SEFIP<3

n(%) SEFIP≥3

n(%) OR 95% CI p-value

Sex: Female

64(59.3)

39(57.4)

0.93

0.50 – 1.71

0.80

Age ≤22 years 23-26 years 27-32 years ≥33 years

34(31.5) 30(27.8) 25(23.2) 19(17.6)

8(11.9) 15(22.4)17(25.4)27(40.3)

1.00 2.13 2.89 6.04

0.79 – 5.71 1.08 – 7.75 2.29 – 15.91

0.14 0.04

0.0003

Low body weight (<18.5 BMI)

34(33.0)

22(32.8)

0.99 0.52 – 1.91 0.98

Low income: Below cut-off

9(8.3)

2(3.0)

0.35

0.07 – 1.66

0.19

Rank: Corps Apprentice Soloist/principal

64(59.3) 10(9.3) 34(31.5)

32(47.1)1(1.5)

35(51.5)

1.00 0.20 2.06

0.03 – 1.63 1.09 – 3.89

0.13 0.03

Number of years dancing total ≤11 years 12-16 years 17-23 years ≥24 years

30(28.0) 35(32.7) 24(22.4) 18(16.8)

8(12.1) 8(12.1) 24(36.4)26(39.4)

1.00 0.86 3.75 5.42

0.29 – 2.56 1.43 – 9.83 2.02 – 14.50

0.78 0.07

0.0008

Number of years dancing professionally ≤3 years 4-8 years 9-15.4 years ≥15.5 years

28(25.9) 36(33.3) 24(22.2) 20(18.5)

7(10.5) 12(17.9)25(37.3)23(34.3)

1.00 1.33 4.17 4.60

0.46 – 3.83 1.53 – 11.321.66 – 12.79

0.59 0.005 0.003

Number of years in present company ≤2 years 3-6 years 7-12 years ≥13 years

32(29.6) 30(27.8) 24(22.2) 22(20.4)

7(10.5) 16(23.9)20(29.9)24(35.8)

1.00 2.44 3.81 4.99

0.88 – 6.75 1.39 – 10.461.83 – 13.58

0.09 0.01 0.002

Company: National Ballet of Canada Royal Swedish Ballet Royal Danish Ballet

35(63.6) 29(52.7) 45(67.2)

20(36.4)26(47.3)22(32.8)

1.00 1.57 0.86

1.00 – 1.00 0.73 – 3.37 0.40 – 1.81

0.25 0.68

54 Table 3.20: Univariate Analysis for SEFIP score of ≥3 (ballet dancers only)

Variable SEFIP<3

n(%) SEFIP≥3

n(%) OR 95% CI p-value

Country: Canada Sweden Denmark *

35(32.1) 29(26.6) 45(41.3)

20(29.4)26(38.2)22(32.4)

1.00 1.57 0.86

0.73 – 3.37 0.40 – 1.81

0.25 0.68

Abbreviations: SEFIP, Self Estimated Functional Inability because of Pain; OR, odds ratio; CI, confidence interval; BMI, body mass index. *Israel not included as there were no participating ballet companies in Israel.

55 Table 3.21: Univariate Analysis for SEFIP score of ≥3(modern dancers only)

Variable SEFIP<3

n(%) SEFIP≥3

n(%) OR 95% CI p-value

Sex: Female

23(51.1)

18(48.7)

0.91

0.38 – 2.16

0.82

Age ≤21 years 22-24 years 25-27 years ≥28 years

8(18.2) 11(25.0) 13(29.6) 12(27.3)

11(30.6)5(13.9) 10(27.8)10(27.8)

1.00 0.33 0.56 0.61

0.08 – 1.34 0.16 – 1.91 0.18 – 2.09

0.12 0.35 0.43

Low body weight (<18.5 BMI)

1(2.3)

2(5.4)

2.40

0.21 – 27.59

0.48

Low income: Below cut-off

6(13.3)

10(27.0)

2.41

0.78 – 7.41

0.13

Number of years dancing total ≤8 years 9-12 years 13-18 years ≥19 years

9(25.0) 13(36.1) 11(30.6) 3(8.3)

11(33.3)7(21.2) 8(24.2) 7(21.2)

1.00 0.44 0.60 1.91

0.12 – 1.57 0.17 – 2.11 0.38 – 9.59

0.21 0.42 0.43

Number of years dancing professionally ≤2 years 3-4 years 5-8 years ≥9 years

8(18.2) 12(27.3) 11(25.0) 13(29.6)

10(27.0)2(5.4)

13(35.1)12(32.4)

1.00 0.13 0.95 0.74

0.02 – 0.77 0.28 – 3.23 0.22 – 2.49

0.03 0.93 0.63

Number of years in present company ≤2 years 3-6 years ≥7 years

22(48.9) 12(26.7) 11(24.4)

15(40.5)11(29.7)11(29.7)

1.00 1.34 1.47

0.47 – 3.84 0.51 – 4.24

0.58 0.48

Country: Canada Sweden Israel *

9(20.0) 11(24.4) 25(55.6)

5(13.5) 5(13.5) 27(51.9)

1.00 0.82 1.94

0.18 – 3.74 0.57 – 6.59

0.80 0.29

Abbreviations: SEFIP, Self Estimated Functional Inability because of Pain; OR, odds ratio; CI, confidence interval, BMI, body mass index. *Denmark not included as there were no participating modern companies in Denmark.

56

3.10.2 Multivariable analysis (logistic regression)

Identical methodology was used as for the previous analysis of self reported injury, but this time

using the outcome variable of SEFIP score of ≥3. The model for the multivariable analysis for

ballet dancers was created based on the results of the univariate analysis. The variables included

in this model are:

Low income, rank, and number of years dancing professionally.

The results of the logistic regression analysis for ballet dancers are reported in Table 3.22. The

variables low income and rank were removed from the model via backwards stepwise regression.

Ballet dancers dancing 9-15.4 years professionally were more likely to have a SEFIP score of ≥3

as ballet dancers dancing ≤3 years professionally (OR = 4.0). This association strengthened with

dancers dancing professionally ≥15.5 years (OR = 4.4).

Table 3.22 Final Model for Logistic Regression Analysis. Factors Associated with SEFIP ≥3

(ballet dancers)

Variable β OR 95% CI p-value Number of years dancing professionally: ≤3 years 4-8 years 9-15.4 years ≥15.5 years Intercept

1.00 0.29 1.39 1.48 -1.39

1.00 1.33 4.00 4.40

0.46 – 3.83 1.47 – 10.91 1.58 – 12.28

0.59 0.007 0.005

Abbreviations: β, beta; SEFIP, Self Estimated Functional Inability because of Pain; OR, odds ratio; CI, confidence interval.

Lastly, a model was created based on the univariate analysis for modern dancers only.

The variables included in this model are:

Low income and number of years dancing professionally.

No variables remained in the model after the logistic regression analysis.

57

3.12 Characteristics of Prevalent Injuries

3.12.1 Body region injured

If dancers had more than one body region injured, they were asked to report the most

problematic body region injured. The same body regions were listed as for the SEFIP. The

results for current most problematic body region injured for dancers are reported stratified by

style and sex in Table 3.23. Results are reported stratified by dance company in Table 3.24.

A similar pattern is noted for all male and female ballet dancers (Table 3.23). The ankles/feet

region has the highest percentage of reported “most problematic injury” followed by knees. This

is followed by either hip or low back regions. Amongst ballet dancers, there was only one

reported upper limb region (shoulders) being a “most problematic injury” and no ballet dancer

reported the neck, elbows, wrists/hands, anterior thighs, shins, or toes as being the “most

problematic injury”.

No similar pattern is noted between the modern dance companies for the “most problematic

injury.”(Table 3.24) In contrast to ballet dancers, neck injuries are reported amongst modern

dancers. The neck is the most frequent body region reported for “most problematic injury” in the

Batsheva Dance Company (45.5%) and Ensemble Batsheva (40.0%). The most frequent region

reported amongst Toronto Dance Theatre dancers is the shoulder region (33.3%). Amongst the

Cullberg Ballet dancers, the knees were the most frequently reported region of injury (37.5%).

No modern dancers reported a problematic injury in the elbows, wrists/hands, anterior thighs, or

shins.

58

Table 3.23: Body Region Injured (current most problematic injury of injured dancers) by

style and sex.

Ballet Modern Body Region Male

n=40 n(%)

Female n=56 n(%)

Male n=19 n(%)

Female n=20 n(%)

Neck

0 0 4(21.1) 6(30.0)

Shoulders

0 1(1.8) 2(10.5) 1(5.0)

Elbows

0 0 0 0

Wrists/hands

0 0 0 0

Upper back

1(2.5) 2(3.6) 1(5.3) 0

Lower back

4(10.0) 6(10.7) 5(26.3) 4(20.0)

Hips

5(12.5) 6(10.7) 3(15.8) 1(5.0)

Ant. Thighs

0 0 0 0

Post. Thighs

1(2.5) 3(5.4) 0 2(10.0)

Knees

7(17.5) 13(23.2) 0 3(15.0)

Shins

0 0 0 0

Calves

0 1(1.8) 1(5.3) 0

Ankles/Feet

22(55.0) 23(41.1) 3(15.8) 1(5.0)

Toes 0 0 0 2(10.0) Only dancers reporting injury were included. All non-dance related injuries have been removed.

59

Table 3.24: Body Region Injured (current most problematic injury of injured

dancers) by company.

Ballet Companies Modern Companies Body Region NBC

N=32 n(%)

RSB N=33 n(%)

RDB N=32 n(%)

TDT N=6 n(%)

CUL N=8 n(%)

BAT N=11 n(%)

ENS N=10 n(%)

Neck

0

0

0

1(16.7)

0

5(45.5)

4(40.0)

Shoulders

0

0

1(3.1)

2(33.3)

0

0

1(10.0)

Elbows

0

0

0

0

0

0

0

Wrists/hands

0

0

0

0

0

0

0

Upper back

1(3.1)

0

2(6.3)

0

1(12.5)

0

0

Lower back

3(9.4)

4(12.1)

4(12.5)

0

2(25.0)

2(18.2)

3(30.0)

Hips

3(9.4)

6(18.2)

2(6.3)

1(16.7)

0

1(9.1)

2(20.0)

Ant. Thighs

0

0

0

0

0

0

0

Post. Thighs

0

3(9.1)

1(3.1)

1(16.7)

1(12.5)

0

0

Knees

6(18.8)

7(21.2)

7(21.9)

0

3(37.5)

0

0

Shins

0

0

0

0

0

0

0

Calves

1(3.1)

0

0

1(16.7)

0

0

0

Ankles/Feet

18(56.3)

12(36.4)

15(46.9)

0

1(12.5)

3(27.3)

0

Toes

0

1(3.0)

0

0

0

0

0

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance

Company; ENS, Ensemble Batsheva; Kibbutz Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 results are not reported due to small sample sizes. Only dancers reporting injury were included. All non-dance related injuries have been removed.

60

3.12.2 Injury Duration

The majority of male and female ballet and modern dancers are reporting chronic injuries,

particularly of ≥ 6 months duration (Table 3.25). Fifty percent of female ballet dancers, 51.3% of

male ballet dancers and 60.0% of female modern dancers reported current injury of ≥ 6 months

duration. The frequency of ≥ 6 months duration was slightly less in modern male dancers

(36.8%) however they had greater frequencies in the 3months - <6 months duration (21.1%) and

29 days - <3months duration (15.8%).

The Ensemble Batsheva was the only company with a higher frequency of injuries in the 8-28

days duration (40.0%) than the ≥ 6 months duration (30.0%) (Table 3.26). The National Ballet

of Canada had the highest frequency of injury duration less than 29 days (40.5%). By contrast,

the Batsheva Dance Company had no reported injury duration of less than 29 days. The Cullberg

Ballet dancers reported injury durations at two extremes with 75.0% in the ≥ 6 months duration

and 25.0% in the 1-7 days duration.

61

Table 3.25 : Duration of Injury (by style and sex)

Ballet Modern Male

N=39 n(%)

Female N=56 n(%)

Male N=19 n(%)

Female N=20 n(%)

1-7 days

2(5.1)

5(8.9)

2(10.5)

1(5.0)

8-28 days

9(23.1) 9(16.1) 3(15.8)

3(15.0)

29 days - <3months

5(12.8) 5(8.9) 3(15.8) 1(5.0)

3months - <6 months

3(7.7) 9(16.1) 4(21.1) 1(5.0)

≥ 6 months

20(51.3) 28(50.0) 7(36.8) 12(60.0)

Only dancers reporting injury were included. All non-dance related injuries have been removed.

Table 3.26 : Duration of Injury (by company)

NBC N=32 n(%)

RSB N=33 n(%)

RDB N=33 n(%)

TDT N=6 n(%)

CUL N=8 n(%)

BAT N=11 n(%)

ENS N=10 n(%)

1-7 days

3(9.4)

0

4(12.1)

1(16.7)

2(25.0)

0

0

8-28 days

10(31.1) 4(12.1) 4(12.1) 1(16.7) 0 0 4(40.0)

29 days - <3months

1(3.1) 3(9.1) 7(21.2) 1(16.7) 0 2(18.2) 2(20.0)

3months - <6 months

4(12.5) 5(15.2) 3(9.1) 0 0 3(27.3) 1(10.0)

≥ 6 months

14(43.8) 21(63.6) 15(45.5) 3(50.0) 6(75.0) 6(54.5) 3(30.0)

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva;

Kibbutz Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 results are not reported due to small sample sizes. Only dancers reporting injury were included. All non-dance related

injuries have been removed.

62

3.12.3 Injury Severity

The highest frequency of reported injury severity was moderate for all injured ballet dancers

with 55.3% of injured male ballet dancers and 48.1% of injured female ballet dancers reporting

moderate injury severity (Table 3.27). Injured modern dancers had similar high reported

frequencies of moderate injury severity with 47.4% of injured male modern dancers and 65.0%

of injured female modern dancers reporting moderate injury severity. Severe injury severity was

reported by 21.1% of injured male ballet dancers and 27.8% of injured female ballet dancers.

Similarly, 21.1% of injured male modern dancers and 25.0% of injured female dancers reported

severe injury.

The Royal Danish Ballet and the Cullberg Ballet had the highest frequencies of injured dancers

reporting their injuries as severe (Table 3.28). Forty percent of injured dancers in the Royal

Danish Ballet and 50.0% of injured dancers in the Cullberg ballet reported severe injury.

3.12.4 Time Off Work in Past Year

The majority of injured male and female modern dancers took either no time off from work in

the past year or 1 to 7 days off work due to their injuries (Table 3.29). Amongst injured modern

dancers, 26.3% of males and 45.0% of females took no time off from work; 42.1% of injured

male modern dancers and 30.0% of injured female modern dancers took 1-7 days off from work

due to their injuries.

Injured ballet dancers reported higher frequencies of time off work compared to injured modern

dancers with 10.3% of injured male ballet dancers and 17.9% of injured female ballet dancers

taking between 3 to 6 months off from work compared to 5.3% of injured male modern dancers

and 5.0% of injured female modern dancers taking between 3 to 6 months off from work due to

their injuries (Table 3.29). No injured modern dancers reported taking more than 6 months off

from work due to their injuries. In contrast, 12.8% of injured male ballet dancers and 5.4% of

injured female ballet dancers took more than 6 months off from work due to their injuries.

63

Higher percentages of injured dancers in the Scandinavian ballet companies took longer periods

of time off work than injured dancers in the National Ballet of Canada with 27.3% of injured

Royal Swedish Ballet Dancers and 16.1% of Royal Danish Ballet dancers taking between 3 to 6

months off from work due to their injuries (Table 3.30). Additionally, 3.0% of injured Royal

Swedish Ballet dancers and 16.0% of injured Royal Danish Ballet dancers took more than six

months off work due to their injuries. In contrast, 3.1% of injured National Ballet of Canada

dancers took 3-6 months off and 6.3% of injured National Ballet of Canada dancers took more

than six months off work due to their injuries.

Amongst modern dance companies, no injured dancers took more than 28 days off work with the

exception of the Batsheva Dance Company in which 27.3% of injured dancers took between 29

days to 3 months off from work and 18.2% of injured dancers took between three and six months

off work due to their injuries (Table 3.30). In the Cullberg Ballet, no dancer took more than one

week off from work with 87.5% of injured dancers taking no time off work due to their injuries.

64

Table 3.27 : Injury Severity (by style and sex)

Ballet Modern Male

N=39 n(%)

Female N=54 n(%)

Male N=19 n(%)

Female N=20 n(%)

Minor

9(23.7)

13(24.1)

6(31.6)

2(10.0)

Moderate

21(55.3) 26(48.1) 9(47.4) 13(65.0)

Severe

8(21.1) 15(27.8) 4(21.1) 5(25.0)

Only dancers reporting injury were included. All non-dance related injuries have been removed.

Table 3.28 : Injury Severity (by company)

NBC N=31 n(%)

RSB N=32 n(%)

RDB N=30 n(%)

TDT N=6 n(%)

CUL N=8 n(%)

BAT N=11 n(%)

ENS N=10 n(%)

Minor

9(29.0)

5(15.6)

8(26.7)

1(16.7)

1(12.5)

2(18.2)

4(40.0)

Moderate

17(54.8) 20(62.5) 10(33.3) 5(83.3) 3(37.5) 6(54.5) 5(50.0)

Severe

5(16.1) 7(21.9) 12(40.0) 0 4(50.0) (27.3) 1(10.0)

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva;

Kibbutz Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 results are not reported due to small sample sizes. Only dancers reporting injury were included. All non-dance related

injuries have been removed.

65

Table 3.30 : Time off work due to current injury in past year (by company)

NBC N=32 n(%)

RSB N=33 n(%)

RDB N=31 n(%)

TDT N=6 n(%)

CUL N=8 n(%)

BAT N=11 n(%)

ENS N=10 n(%)

None

11(34.4) 14(42.4) 4(12.9) 3(50.0) 7(87.5) 1(9.1) 2(20.0)

1-7 days

6(18.8) 5(15.2) 5(16.1) 2(33.3) 1(12.5) 3(27.3) 7(70.0)

8-28 days

8(25.0) 2(6.1) 6(19.4) 1(16.7) 0 2(18.2) 1(10.0)

29 days - <3months

4(12.5) 2(6.1) (19.4) 0 0 3(27.3) 0

≥3months - <6 months

1(3.1) 9(27.3) 5(16.1) 0 0 2(18.2) 0

≥6 months 2(6.3) 1(3.0) 5(16.1) 0 0 0 0 Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva; Kibbutz Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 results are not reported due to small sample sizes. Only dancers reporting injury were included. All non-dance related injuries have been removed.

Table 3.29: Time off work due to current injury in past year (by style and sex)

Ballet Modern Male

N=39 n(%)

Female N=56 n(%)

Male N=19 n(%)

Female N=20 n(%)

None

13(33.3) 16(28.6) 5(26.3) 9(45.0)

1-7 days

5(12.8) 11(19.6) 8(42.1) 6(30.0)

8-28 days

9(23.1) 7(12.5) 3(15.8) 2(10.0)

29 days - <3months

3(7.7) 9(16.1) 2(10.5) 2(10.0)

≥3months - <6 months

4(10.3) 10(17.9) 1(5.3) 1(5.0)

≥6 months 5(12.8) 3(5.4) 0 0 Only dancers reporting injury were included. All non-dance related injuries have been removed.

66

3.12.5 Recurrent Injuries

Dancers were asked whether they have had this current injury previously (recurrent injury).

Amongst injured ballet dancers, 48.7% of males and 57.1% of females report recurrent injury

(Table 3.31). Amongst injured modern dancers, 68.4% of males and 44.4% of females report

recurrent injury. Frequency of reported recurrent injury varied between dance companies.

Amongst ballet companies, injured dancers in the Royal Swedish Ballet reported the highest

frequency of recurrent injury (72.7%) compared with 54.8% of injured dancers in the Royal

Danish Ballet reporting recurrent injury and 34.4% of injured dancers in the National Ballet of

Canada reporting recurrent injury (Table 3.32). Reported recurrent injury also varied amongst

modern dance companies with 100.0% of injured dancers of the Toronto Dance Theatre

reporting recurrent injury compared to 66.7% of injured dancers in the Batsheva Dance

Company, 50.0% of dancers in the Ensemble Batsheva and 25.0% of injured dancers in the

Cullberg Ballet reporting recurrent injury.

67

Table 3.31 : Recurrent Injury (by style and sex) Ballet Modern Male

N=39 n(%)

Female N=56 n(%)

Male N=19 n(%)

Female N=18 n(%)

No

20(51.3)

24(42.9)

6(31.6)

10(55.6)

Yes

19(48.7)

32(57.1)

13(68.4)

8(44.4)

Only dancers reporting injury were included. All non-dance related injuries have been removed.

Table 3.32 : Recurrent Injury (by company) NBC

N=32 n(%)

RSB N=33 n(%)

RDB N=31 n(%)

TDT N=6 n(%)

CUL N=8 n(%)

BAT N=9 n(%)

ENS N=10 n(%)

No

21(65.6)

9(27.3)

14(45.2)

0

6(75.0)

3(33.3)

5(50.0)

Yes

11(34.4)

24(72.7)

17(54.8)

6(100.0)

2(25.0)

6(66.7)

5(50.0)

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva;

Kibbutz Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 results are not reported due to small sample sizes. Only dancers reporting injury were included. All non-dance related

injuries have been removed.

68

3.13 Relationship between SEFIP scores and SRI The frequency of the highest reported SEFIP score reported by injured and non-injured dancers

is reported in Table 3.33. The majority of ballet and modern dancers who have reported being

injured do report SEFIP scores of 3 or 4 denoting some degree of functional impairment.

Between 30.0% to 36.8% of injured ballet and modern dancers reported injury with a highest

SEFIP score of 2 which denotes significant pain but no functional compromise.

The majority of dancers who considered themselves “not injured” had a SEFIP score of 2 or less.

However, 13.7% of “not injured” female ballet dancers had a SEFIP score of 3 compared to

7.7% of “not injured” male ballet dancers. Of the “not injured” modern dancers, 33.3% of males

and 27.3% of females had a SEFIP score of 3. Overall, 19.8% of all “not injured” dancers had a

SEFIP score of 3.

Table 3.33: Highest Reported SEFIP Score for Injured and Non-injured Dancers

Ballet Modern Injured Not Injured Injured Not Injured SEFIP score

Male N=47 n(%)

Female N=52 n(%)

Male N=26 n(%)

Female N=26 n(%)

Male N=20 n(%)

Female N=19 n(%)

Male N=21 n(%)

Female N=22 n(%)

0 0 0 2(7.7) 0 0 0 0 0 1 4(8.5) 5(9.6) 8(30.8) 19(37.3) 2(10.0) 0 7(33.3) 9(40.9) 2 16(34.0) 16(30.8) 14(53.8) 2(49.0) 6(30.0) 7(36.8) 7(33.3) 7(31.8) 3 18(38.3) 28(53.8) 2(7.7) 7(13.7) 12(60.0) 10(52.6) 7(33.3) 6(27.3) 4 9(19.1) 3(5.8) 0 0 0 2(10.5) 0 0 0 = “very well”; 1 = “some pain but not much problem”; 2 = “pretty much pain but I can handle it”; 3 = “much pain, must avoid some movements”; 4 = “cannot work in the production because of pain”. Abbreviations: SEFIP, Self-Estimated Functional Inability because of Pain

3.14 Reporting of Dance-related Injuries Frequency of dancers who have not reported their injury is detailed in Table 3.34. The aggregate

percentage of ballet dancers who have not reported an injury is 15.5%. Amongst the modern

dance companies, the Toronto Dance Theatre has a much higher percentage of dancers not

reporting an injury (66.7%) as compared to the other modern dance companies.

69

Reasons why a dancer has not reported an injury are reported in Table 3.35. All the options given

were chosen as reasons for not reporting an injury (Appendix 2, Section D). The four most cited

reasons overall for both ballet and modern dancers were: “It did not affect my work”, “Pain is an

inherent part of dancing”, “I can cope with the pain”, and “I did not want to stop dancing”.

For those dancers who have reported an injury, the results of to whom dancers are reporting their

injury are listed in Table 3.36. Twelve dancers reported to “other” which included: assistant to

the artistic director, ballet secretary, choreographer, insurance company, government, stage

manager, and teacher.

Table 3.37 reports the frequency of all injuries reported to the local workers’ compensation

board or national insurance as a work injury by company. Injuries were reported as work injuries

only in the Scandinavian ballet companies and the Batsheva Dance Company in Israel.

Table 3.34: Frequency of non-reported injuries

Injuries not reported by dancers n(%)

Ballet dancers (N=97)

15(15.5)

National Ballet of Canada (N=32)

4(12.5)

Royal Swedish Ballet (N=33)

6(18.2)

Royal Danish Ballet (N=32) 5(15.6) Modern dancers (n=39)

7(17.9)

Toronto Dance Theatre (N=6)

4(66.7)

Cullberg Ballet (N=8)

1(12.5)

Batsheva Dance Company (N=11)

1(9.1)

Ensemble Batsheva (N=10)

1(10.0)

Only injured dancers. Non-dance related injuries removed.

70

Table 3.35: Reasons for not reporting an injury.

Reason for not reporting an injury: Ballet

N=15 n(%)

Modern N=7 n(%)

I did not feel it was important.

3(20.0) 2(28.6)

It did not affect my work.

6(40.0) 5(71.4)

I did not want to be seen as unreliable.

3(20.0) 2(28.6)

Pain is an inherent part of dancing.

5(33.3) 5(71.4)

I did not want to negatively affect the production.

3(20.0) 1(14.3)

I can cope with the pain.

8(53.3) 7(100.0)

I did not want to stop dancing.

4(26.7) 5(71.4)

I did not want to lose a role.

2(13.3) 2(28.6)

I did not want to let my company down.

2(13.3) 2(28.6)

Other 1(7.1) 0 Only injured dancers who stated they did not report their injury are

included. Non-dance related injuries removed.

71

Table 3.36: To whom are dancers reporting their injuries? Ballet dancers

Modern dancers

NBC (N=28) n(%)

RSB (N=27) n(%)

RDB (N=27) n(%)

TDT (N=2) n(%)

CUL (N=7) n(%)

BAT (N=10) n(%)

ENS (N=9) n(%)

Rehearsal Director

22(78.6) 11(40.7) 19(70.4) 1(50.0) 5(71.4) 10(100.0) 9(100.0)

Company Manager

7(25.0) 2(7.4) 10(38.5) 1(50.0) 2(28.6) 6(60.0) 1(11.1)

Artistic Director

16(57.1) 13(48.1) 17(65.4) 1(50.0) 5(71.4) 7(70.0) 3(33.3)

Company Health Professional

24(85.7) 26(96.3) 24(88.9) 0 2(28.6) 10(100.0) 5(55.6)

Health Professional not related to company

16(57.1) 11(40.7) 5(20.0) 2(100.0) 4(57.1) 3(30.0) 2(22.2)

Other

5(18.5) 5(18.5) 1(4.0) 1(50.0) 0 0 0

Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva.

Kibbutz Dance Company and Kibbutz Dance Company 2 results not detailed due to low response rates.

72

Table 3.37: Injuries Reported as Work Injuries

Injuries reported as work injuries n(%)

Ballet

National Ballet of Canada (N=32)

n/a

Royal Swedish Ballet (N=33)

10(30.3)

Royal Danish Ballet (n=32)

16(50.0)

Modern

Toronto Dance Theatre (N=6)

0

Cullberg Ballet (N=8)

0

Batsheva Dance Company (N=10)

3(30.0)

Ensemble Batsheva (N=10)

0

Kibbutz Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 results are not reported due to small sample sizes. Only dancers reporting injury were included. All non-dance related

injuries have been removed.

73

3.15 Dancers’ Attitudes and Perceptions of Injury

Tables 3.38 reports dancers’ responses to agree/disagree scales of various attitudinal questions

regarding injury and dance-related pain stratified by style and self-reported injury status. The

results are summarized in aggregate format for all dancers as follows:

1. The majority of dancers (80.6%) disagree with the statement: “I consider myself injured if I

have any pain when I dance.”

2. The majority of dancers agree (70.4%) with the statement “I consider myself injured if I must

modify movements when I dance due to pain”. However, a significant number of dancers

disagree (29.6%) with this statement, especially those who are not injured.

3. The majority of dancers agree (72.8%) with the statement “I consider myself injured if I miss

a company class or rehearsal due to dance-related pain.” However, a significant number of

dancers disagree (27.1%) with this statement.

4. The majority of dancers agree (70.8%) with the statement “I consider myself injured if I must

take medication due to my dance-related pain.” However, a significant number of dancers

disagree (29.2%) with this statement, especially ballet dancers.

5. The majority of dancers agree (56.9%) with the statement, “I consider myself injured if I must

seek care from a health-care practitioner for my dance-related pain.” However, a significant

number of dancers do disagree (43.1%) with this statement.

6. The majority of dancers agree with the following statements:

a. “I consider myself injured if I miss more than one day of work due to dance-related

pain.” (Agree: 81.3%; Disagree: 11.7%). Ballet dancers were more likely to disagree

with this statement than modern dancers.

74

b. “I consider myself injured if I have visual signs such as redness or swelling that

accompany my pain.” (Agree: 85.1%; Disagree: 14.9%). Modern dancers were more

likely to disagree with this statement than ballet dancers.

7. Dancers overwhelmingly agree about the following two statements:

a. “I consider myself injured if I a m unable to participate in a performance due to

dance- related pain.” (Agree: 96.8%; Disagree: 3.2%)

b. “I consider myself injured if I must go to the hospital due to my dance-related pain.”

( Agree: 97.3%; Disagree: 2.7%)

Table 3.38: Responses to Attitudinal Questions I consider myself injured if I…. Style Injury

Status Strongly

Agree n(%)

Agree

n(%)

Mildly agree n(%)

Mildly disagree

n(%)

Disagree

n(%)

Strongly disagree

n(%) Injured (N=99)

3(3.0) 5(5.1) 17(17.2) 9(9.1) 43(43.4) 22(22.2) Ballet

Not injured (N=85)

0 1(1.3) 8(10.4) 10(13.0) 33(42.9) 25(32.5)

Injured (N=39)

0 3(7.7) 7(17.9) 8(20.5) 14(35.9) 7(17.9)

… have any pain when I dance.

Modern

Not injured (N=43)

0 2(4.7) 4(9.3) 5(11.6) 25(58.1) 7(16.3)

Injured (N=98)

13(13.3) 30(30.6) 36(36.7) 6(6.1) 12(12.2) 1(1.0) Ballet

Not injured (N=77)

3(3.8) 27(34.6) 17(21.8) 16(20.5) 12(15.4) 2(2.6)

Injured (N=39)

4(10.3) 11(28.2) 15(38.5) 8(20.5) 0 1(2.6)

… must modify movements when I dance due to pain.

Modern

Not injured (N=43)

3(7.0) 12(27.9) 10(23.3) 9(20.9) 9(20.9) 0

75

Table 3.38: Responses to Attitudinal Questions I consider myself injured if I…. Style Injury

Status Strongly

Agree n(%)

Agree

n(%)

Mildly agree n(%)

Mildly disagree

n(%)

Disagree

n(%)

Strongly disagree

n(%) Injured (N=99)

17(17.2) 28(28.3) 22(22.2) 10(10.1) 20(20.2) 2(2.0) Ballet

Not injured (N=77)

12(15.6) 26(33.8) 15(19.5) 10(13.0) 10(13.0) 4(5.2)

Injured (N=39)

6(15.4) 20(51.3) 10(25.6) 0 3(7.7) 0

…miss a company class or rehearsal due to dance-related pain.

Modern

Not injured (N=43)

6(14.0) 20(46.5) 6(14.0) 3(7.0) 5(11.6) 3(7.0)

Injured (N=99)

18(18.2) 40(40.4) 18(18.2) 10(10.1) 12(12.1) 1(1.0) Ballet

Not injured (N=77)

11(14.3) 36(46.8) 12(15.6) 7(9.1) 10(13.0) 1(1.3)

Injured (N=39)

13(33.3) 18(46.2) 6(15.4) 1(2.6) 1(2.6) 0

…miss more than one day of work due to dance-related pain.

Modern

Not injured (N=43)

11(25.6) 25(58.1) 2(4.7) 2(4.7) 3(7.0) 0

76

Table 3.38: Responses to Attitudinal Questions I consider myself injured if I…. Style Injury

Status Strongly

Agree n(%)

Agree

n(%)

Mildly agree n(%)

Mildly disagree

n(%)

Disagree

n(%)

Strongly disagree

n(%) Injured (N=99)

49(49.5) 42(42.4) 6(6.1) 1(1.0) 1(1.0) 0 Ballet

Not injured (N=77)

35(45.5) 33(42.9) 4(5.2) 2(2.6) 2(2.6) 1(1.3)

Injured (N=39)

25(64.1) 12(30.8) 2(5.1) 0 0 0

… am unable to participate in a performance due to dance-related pain.

Modern

Not injured (N=43)

26(60.5) 14(32.6) 2(4.7) 0 1(2.3) 0

Injured (N=98)

19(19.4) 24(24.5) 23(23.5) 14(14.3) 18(18.4) 0 Ballet

Not injured (N=77)

11(14.3) 19(24.7) 19(24.7) 12(15.6) 13(16.9) 3(3.9)

Injured (N=39)

13(33.3) 12(30.8) 8(20.5) 4(10.3) 2(5.1) 0

…must take medication due to my dance-related pain.

Modern

Not injured (N=43)

14(32.6) 7(16.3) 13(30.2) 3(7.0) 6(14.0) 0

77

Table 3.38: Responses to Attitudinal Questions I consider myself injured if I…. Style Injury

Status Strongly

Agree n(%)

Agree

n(%)

Mildly agree n(%)

Mildly disagree

n(%)

Disagree

n(%)

Strongly disagree

n(%) Injured (N=99)

16(16.2) 17(17.2) 19(19.2) 16(16.2) 27(27.3) 4(4.0) Ballet

Not injured (N=77)

10(13.0) 22(28.6) 10(13.0) 17(22.1) 14(18.2) 4(5.2)

Injured (N=39)

3(7.7) 15(38.5) 12(30.8) 6(15.4) 3(7.7) 0

…must seek care from a health-care practitioner for my dance-related pain.

Modern

Not injured (N=43)

2(4.7) 9(20.9) 12(27.9) 6(14.0) 11(25.6) 3(7.0)

Injured (N=99)

61(61.6) 29(29.3) 6(6.1) 3(3.0) 0 0 Ballet

Not injured (N=77)

42(54.5) 24(31.2) 8(10.4) 2(2.6) 1(1.3) 0

Injured (N=39)

24(61.5) 13(33.3) 2(5.1) 0 0 0

… must go to the hospital due to my dance-related pain.

Modern

Not injured (N=43)

23(53.5) 17(39.5) 2(4.7) 0 0 1(2.3)

78

79

Table 3.38: Responses to Attitudinal Questions I consider myself injured if I…. Style Injury

Status Strongly

Agree n(%)

Agree

n(%)

Mildly agree n(%)

Mildly disagree

n(%)

Disagree

n(%)

Strongly disagree

n(%) Injured (N=98)

26(26.5) 37(37.8) 21(21.4) 8(8.2) 6(6.1) 0 Ballet

Not injured (N=75)

19(25.3) 32(42.7) 17(22.7) 3(4.0) 3(4.0) 1(1.3)

Injured (N=39)

13(33.3) 13(33.3) 7(17.9) 2(5.1) 2(5.1) 2(5.1)

… have visual signs such as redness or swelling that accompany my pain.

Modern

Not injured (N=43)

8(18.6) 13(30.2) 11(25.6) 7(16.3) 3(7.0) 1(2.3)

80

3.16 Company Contextual Information

Company contextual information for the 2007-2008 season is detailed in Table 3.39 for easy

comparison. The participating ballet companies range in size from 67 to 83 dancers, whereas the

modern dance companies are smaller ranging in size from 12 to 20 dancers. However, the

number of performance and productions per season are not dependent on the size of the

company. The Royal Danish Ballet had the highest number of performances overall with 153

total performances and 12 separate productions for the 2008 season. The Ensemble Batsheva had

the second highest number with 120 performances for the season and eight productions. The

Toronto Dance Theatre had the lowest number of performances with 30 for the season and four

productions.

Daily company class is required in all companies with the exception of the Royal Danish Ballet

and the National Ballet of Canada; however, dancers are still expected to attend the class. Onsite

healthcare treatment is available at the workplace for all the ballet companies as well as the

Kibbutz Contemporary Dance Companies. The Royal Danish Ballet was the only company to

have “sick classes” specifically for injured dancers.

The number of weeks of vacation also varied greatly ranging from a low of three weeks for the

National Ballet of Canada dancers to a high of 12 weeks for the Royal Danish Ballet and Toronto

Dance Theatre dancers. The ballet dance company dancers all belong to unions as well as the

Cullberg Ballet dancers. No other modern dance companies were unionized. The Royal Swedish

Ballet is the only company to perform on a raked (sloped) stage in their home theatre. Studios for

training and rehearsals are also raked at the Royal Swedish Ballet.

Table 3.39 : Company Contextual Data for the 2007-08 Season Dance Company

Size of Company

(# of dancers)

Performances/ year

Productions/ year

Daily Company

Class

Onsite treatment available?

Weeks vacation/year.

Dancers Unionized?

“Sick Classes”

for injured dancers

Raked Stage?

Ballet:

NBC

69 85 4 Optional Yes 3 Yes No No

RSB

67 73 8 Required Yes 10 Yes No Yes

RDB

83 153 12 Optional Yes 12 Yes Yes No

Modern:

TDT

16 30 4 Required No 12 No No No

CUL

20 55 8 Required No 6 Yes No No

BAT

20 110 8 Required No 6 No No No

ENS

15 120 8 Required No 6 No No No

KDC

17 70 6 Required Yes 4 No No No

KDC2 12 100 4 Required Yes 4 No No No Abbreviations: NBC, National Ballet of Canada; RSB, Royal Swedish Ballet; RDB, Royal Danish Ballet; TDT, Toronto Dance Theatre; CUL, Cullberg

Ballet; BAT, Batsheva Dance Company; ENS, Ensemble Batsheva; KDC, Kibbutz Contemporary Dance Company; KDC2, Kibbutz Contemporary Dance Company 2

81

82

Chapter 4: Discussion

4.1 Principal Findings

Prevalence of Injury

Almost all of the dancers in this study reported some degree of current dance-related pain. This

finding is consistent with the findings reported previously in the literature.4, 13 This is one of the

largest cross-sectional studies of musculoskeletal injury in professional ballet and modern

dancers. I have focused specifically on point prevalence in order to reduce recall bias. A study of

Australian athletes found that only 61% were able to remember the number, body region and

diagnoses of injuries sustained in the previous 12 months. 53

The point prevalence of dance-related musculoskeletal injury in dancers is high using two

distinct outcomes for injury, and the estimate varies by case definition. The point prevalence of

self-reported injury was higher than the point prevalence of SEFIP ≥3 injury in all companies

with the exception of the Kibbutz Contemporary Dance Company and the Kibbutz

Contemporary Dance Company 2. The prevalence estimates for these two companies must be

interpreted with caution as these were the two companies that had the lowest response rates. It is

possible that due to the difficult circumstances on the day of the survey, injured dancers left to

deal with their injuries and did not participate. Self reported injury and SEFIP injury estimates

may have been higher if that was indeed the case in this group. I have calculated the prevalence

rates of self-reported injury with the assumption that all non-participants in the Kibbutz

Contemporary Dance Company and Kibbutz Contemporary Dance Company 2 would have

considered themselves injured. Under this assumption, the prevalence (with 95% CI) of self-

reported injury would increase from 9.1% to 41.1% (17.8 - 64.6) and from 37.5% to 58.3% (30.4

– 86.2) respectively. If these non-participants were to have reported SEFIP scores ≥3 as well,

the Kibbutz Contemporary Dance Company prevalence of SEFIP ≥3 injury would increase from

54.5% to 70.6% (48.9 – 92.3) and the Kibbutz Contemporary Dance Company prevalence would

remain at 100.0%. However, cultural attitudes towards pain and injury may also account for this

difference given that the Kibbutz Contemporary Dance Companies had the highest overall

percentage of dancers native to that country (Table 3.4). Cultural and racial differences in

perception of pain and injury have been reported in various cultures.54

82

83 Injury Patterns

Injury patterns differ between professional ballet and modern dancers. The injury patterns for

self-reported injury in professional ballet dancers are consistent with previous findings in the

literature.4 However, professional modern dancers do not have a distinct pattern with and the

frequency of injury for specific body regions differs between modern companies. Although there

are variations between specific schools of ballet, for the most part, ballet is a fairly uniform

language of movement. Modern dance however originated as a rebellion against ballet and there

are many different types of techniques or schools that vary widely from one another. This

variation in repertoire and style of modern dance between the companies participating in this

study likely explains the variation in the types of injuries that dancers in a particular modern

dance company experienced. It is interesting to note that at the time the survey was performed,

the Royal Danish Ballet was performing a mixed repertoire evening that included a modern

dance piece by the choreographer of the Batsheva Dance Company, yet their injury patterns did

not deviate significantly from those of other ballet companies.

Factors Associated with Injury

This is the largest cross-sectional study of professional ballet and modern dancers to make use of

a multivariable analysis to investigate factors independently associated with dance-related injury.

It is important to note that these factors did vary with the two different case definitions used.

Rank was independently associated with self reported injury in ballet dancers with soloists and

principal dancers more likely to report injury than corps de ballet dancers. Ramel et al had a

similar finding in professional Swedish ballet dancers.14 This may be explained by the more

challenging roles that soloists and principal dancers perform. Additionally, the pressure to

continue to dance even when injured may be greater for soloists and principal dancers if there is

no understudy.

There was a trend for female ballet dancers to be less likely to be injured for the self-reported

injury outcome, although the results were not statistically significant. This may be explained by

the higher percentage of female ballet dancers with a SEFIP score of ≥3 that did not consider

themselves injured (Table 3.41). Hamilton et al. found differences in personality traits between

male and female ballet dancers.18 They report that male ballet dancers have more negative

personality traits and psychological distress than female dancers or men in the general

population. Female ballet dancers were reported to have been more adjusted than male ballet

84 dancers, as well as tough-minded, disciplined, and caring than the male ballet dancers.18 It is

possible that these traits may play a role in their perception of injury. It is also possible that

physiological differences in female body types may make them less susceptible to injury than

male ballet dancers. For example, greater flexibility or bone and joint structure in females may

make them more able to attain the typical ideal aesthetic requirements in ballet such as turn out

at the hips. However, these physiological differences have not yet been shown to be associated

with injury in dancers.

Number of years dancing professionally was independently associated with injury in ballet

dancers for the SEFIP ≥3 outcome. The longer one is exposed to dancing at an elite professional

level, the more likely one is to have functional difficulties due to the rigorous physical strain

dancers put their bodies through.

For modern dancers, the only factor that was found to be associated with self-reported injury was

company. The Kibbutz Contemporary Dance Company was less likely to report injury than

dancers in the Toronto Dance Theatre. The reason for this association can be seen clearly from

the prevalence estimates with the Kibbutz Contemporary Dancers reporting very low frequencies

of self-reported injury as mentioned previously. This association was not found with the

SEFIP≥3 outcome.

Injury Characteristics and Time-loss from Work

The majority of injured ballet and modern dancers reported injuries of longer than three months

duration. This suggests that the majority of injuries in both ballet and modern dancers are of a

chronic nature. Additionally, between 21-28% of all injured dancers consider their injury severe

in nature. However, there is a disconnect in certain instances between the injury severity rating

and the amount of time that dancers are taking off work due to their injury. Very few modern

dancers are taking any extended time off work due to their injuries. In fact, in the Cullberg

Ballet, although 50% of injured dancers rated their injuries as severe, only one dancer took a

week off of work while the remaining 87.5% of injured dancers reported taking no time off work

due to their injury in the preceding year.

Scandinavian ballet dancers and dancers in the Batsheva Dance Company were more likely to

take extended amounts of time off work due to their injuries. Societal support may help to

85 explain this ability to take time off work when injured. Scandinavian dancers have better overall

job security and social support than dancers in Canada and Israel.3 Israel likely lies somewhere

between Scandinavia and Canada regarding both social support for injured dancers as well as job

security for injured dancers. However, this does not explain the reason why Cullberg Ballet

dancers are not taking very much time off from work, as it is a Swedish dance company with the

same social and health benefits for injured dancers as the Royal Swedish Ballet. A likely reason

for this difference may lie in the make-up of the company members. The Cullberg Ballet had the

lowest percentage of dancers from the country of the dance company with only 31.3% of their

dancers of Swedish origin. Foreign dancers may either not understand the benefits they have,

may have different cultural attitudes towards these social benefits, or may not yet have access to

the full job security benefits if they have not been in the company for a minimum of three years.

In this case, the median number of years in the present company for Cullberg Ballet dancers was

2.5 years compared to 7.5 years for dancers in the Royal Swedish Ballet.

The size of the company may also influence the ability of a dancer to take any extended time off

work when injured. Although the Royal Danish Ballet has the highest number of performances

per year (153), it also has the largest number of dancers (83). Therefore, they have the ability to

substitute dancers in roles in each work. The Ensemble Batsheva performs 120 performances per

year, yet has a much smaller number of dancers (15). This may significantly increase the number

of performances per year that each individual dancer performs as well as the amount of rehearsal

hours for each dancer. However, this may also increase the amount of pressure on the individual

injured dancer to return to work quickly.

Healthcare and Pain Medication Use

The majority of professional dancers overall are receiving treatment for their dance related pain

and primarily from physiotherapists and massage therapists. Very few ballet dancers were

receiving care from medical doctors and no modern dancers reported receiving care from

medical doctors. The difference in health care use between these groups may be due to the

availability of medical doctor (MD) care. All of the ballet companies had an MD on-site at least

once a week whereas no modern dance company provided access to onsite medical doctor care.

The lower use of medical doctor care compared to other types of healthcare may be also due in

part to the nature of the injures if they are primarily chronic overuse type of injuries. Therefore, a

medical doctor may refer the dancer for physiotherapy or rehabilitation and only continue to

86 follow those injuries which are acute in nature or may require surgery. Dancers may also have

been referred for physiotherapy for previous injuries and due to the ease of access to

physiotherapy care, choose to first attempt care with a physiotherapist.

A large percentage of dancers are using pain medication for their dance-related pain. This figure

was especially high in Canadian dancers with over 50% using pain medication for dance-related

pain at the time of data collection. The reason for higher use of pain medications in Canadians is

unclear however this may possibly be due to cultural differences.

Injury Reporting

More than 15% of injured ballet and modern dancers did not report their injuries. Two of the four

most cited reasons for not reporting an injury (“Pain is an inherent part of dancing” and “I can

cope with the pain”) may indicate that dancers believe pain is part and parcel of their working

lives. The reason “I did not want to stop dancing” may be a red flag, however, for the pressure

that dancers feel to continue to dance despite being in significant pain and considering

themselves injured. Additional reported reasons that may point to a psychosocial component for

not reporting injury include: “I did not want to be seen as unreliable”, “I did not want to

negatively affect the production”, “I did not want to lose a role”, and “I did not want to let my

company down”. Of those dancers who did report their injuries, most did so to either the

rehearsal directors or company health professionals (in those companies that had a company

health professional).

Of additional interest is the fact that 50% of injured Danish dancers had reported their injuries to

the local worker’s compensation board followed by 30% in the Royal Swedish Ballet and the

Batsheva Dance Company. No Canadian dancers had injuries reported to the worker’s

compensation board. The National Ballet of Canada dancers are not eligible for workers’

compensation because they are primarily contract workers. However, no dancers from the

Toronto Dance Theatre had reported an injury that was reported to the workers’ compensation

board as well.

Attitudes Towards Injury

This is also one of the first studies to explore professional dancers’ attitudes towards injury. Pain

alone is not an indicator of injury for professional dancers. For the most part, dancers agreed they

87 would consider themselves injured if they could not perform or had to go to hospital due to

dance-related pain with only a few dancers disagreeing with these statements. The majority of

dancers also agreed they would consider themselves injured if they had visual signs such as

redness and swelling accompanying their pain, had to seek healthcare, or had to take medications

due to their pain. However, many dancers disagreed with these statements. Additionally,

attitudes regarding time-loss from work and functional changes besides not being able to perform

were varied. Most dancers agreed they would consider themselves injured if they missed more

than one day of work, missed company class or rehearsal, or had to modify their movements due

to pain, but many dancers also disagreed with these statements.

88

4.2 Implications of Principal Findings

The difference in prevalence estimates for two different injury outcomes points to the importance

of case definition in dance injury and surveillance research. Future prospective as well as cross-

sectional studies should use clear definitions of injury. Due to the variations in attitudes and

perceptions towards injury seen in this population of dancers, I suggest incorporating a broad

definition of injury in order to capture as many injured dancers as possible. These injuries can

then be subdivided as Bronner et al. have suggested if the dancer has lost time from work, sought

healthcare for their injury, has financial loss from their injury, or has only a physical complaint.36

Functional impairment alone may be problematic as a definition to capture and study injured

dancers as many dancers are continuing to dance with pain and may potentially be injured. As a

significant number of dancers do not consider themselves injured even when modifying

movement due to pain, they may resist reporting themselves as injured. Additionally, time-loss

from work alone should not be used as a definition to capture and study injured dancers as the

results suggest that some injured dancers may not be losing any time from work.

The prevalence of dance-related pain and injury is very high regardless of the definition and the

long-term consequences of this are unknown. Additionally, injured dancers are reporting very

long injury durations, many beyond six months, suggesting chronic injury. Therefore, there is an

urgent need to investigate interventions to help control injury and understand the long-term

implications of these conditions. There is preliminary evidence that comprehensive injury

management and prevention programs for both professional ballet and modern dancers may

decrease injury incidence as well as economic costs associated with injury.25, 27, 28 However these

studies are uncontrolled observational designs and therefore the conclusions are limited.

Since injury patterns vary between professional modern dance companies, a tool such as the

SEFIP may be useful for seasonal planning. Modern dance companies will often have visiting

choreographers as well as repertoire that varies from season to season. Using a tool such as the

SEFIP can help to identify which body areas are more likely to be injured during a certain

production. If that production is repeated later in the season or in a subsequent season, these

injury types can then be anticipated. This could be useful in planning repertoire or identifying

and modifying choreography to help minimize injury. Ramel suggested that dancers with a

SEFIP score of 2 or more be examined by a dance science professional.40 The SEFIP could be

89 useful for the dance company health professionals to assist in identifying dancers that continue to

work with functional issues (SEFIP score ≥3) yet are reluctant to consider themselves injured as

may have been the case in this study with the dancers in the Kibbutz Contemporary Dance

Companies. These dancers might be targeted for increased confidential surveillance and

treatment of their injuries.

This study suggests that rank is independently associated with injury in ballet dancers. Dance

health professionals should aim to identify the special needs of these dancers in their injury

prevention and rehabilitation programs. The number of years dancing professionally was also

found to be independently associated with a SEFIP score ≥3 in ballet dancers. Efforts should be

made to support older and more experienced dancers deal with their injuries. As injury may

possibly lead to the end of a career for a dancer, this support should include physical as well as

psychological components. These findings need to be confirmed in a prospective study design to

determine if the associated factors are indeed risk factors for injury.

It is clear that the high prevalence of reported injury, lengthy reported injury durations, and in

some cases extended time off work due to these injuries, places a high burden on the dance

companies themselves to deal with their injured workers. The discrepancy however between the

higher percentages of ballet dancers taking extended time off from work due to their injuries

compared to modern dancers is concerning. This discrepancy is also seen between the amount of

time that ballet dancers in the Scandinavian countries were off work due to their injuries

compared to ballet dancers in Canada. This suggests that company or country level factors may

play a role in the ability of a dancer to take the appropriate time off to recover from an injury.

This may in turn have an effect on future injury or potentially a shortened career. The difference

in access to benefits and frequency of reporting of injuries as work injuries between the countries

supports this need for further exploration of these societal and company level factors. Although

the social benefits in Scandinavian countries are vastly different than in Canada or Israel, all

dance companies should strive to provide their dancers with job security and the ability to take

the appropriate time off work to recover from injuries as recommended by healthcare

professionals. This responsibility does not lie however with the dance company alone.

Government support for dance and the arts in general is higher in Scandinavian countries than in

Israel or Canada. Governments should be aware of the high burden of pain and injury in

professional dancers and strive to increase the needed support to these populations.

90

Larger studies are needed to investigate these higher level company and country factors with

multi-level modeling. This will help to determine if factors such as number of performances,

productions, availability of social or medical support or other company or country level factors

are associated with injury. In the meantime however, smaller companies with high numbers of

performances and productions should be aware that their dancers may have an increased dance

exposure compared to dancers in larger companies or companies with smaller number of

performances or productions. Efforts to decrease this exposure and potentially decrease injury in

these dancers should include increasing the number of dancers in the company and/or decreasing

the number of performances per season. Exposure to dance is more easily measured in a

prospective study, and a better measure of exposure involves time at risk. Ideally, time-based

exposure should be evaluated by determining number of injuries per 1000 hours of dance-

participation as has been adopted by many European sports injury researchers.36

Two subsets of dancers have been identified that are of special concern. These are dancers who

are not reporting their injuries and dancers who are dancing through pain and functional issues

potentially as a result of their attitudes towards injury. The fact that more than 15% of all injured

professional dancers have not reported their injuries is very important as this affects all measures

of injury prevalence and incidence. Future studies of musculoskeletal injury in dancers should

keep this in mind when deciding how best to capture injured dancers. Dance injury registries

should make efforts to use those individuals that dancers are most likely to report their injuries

to, such as rehearsal directors and company health professionals. Rehearsal directors often have

the most work contact with dancers and therefore a high level of trust may be developed.

Dancers may also be very trusting of company health professionals due to the guarantee of

confidentiality. Of the reasons given for not reporting an injury, “I did not want to stop dancing”

especially deserves further attention. This may point towards a fear of dealing with or accepting

the possibility of injury and possibly losing time from work. This may cause a dancer to continue

to dance with pain and possibly ignore warning signs of injury. Additional reasons reported point

towards psychosocial pressures within the company. It is clear that there is a need for

professional dance companies to develop measures that allow dancers, who are in pain and may

be injured, to feel comfortable and secure enough to report their injuries.

91 The attitudinal results suggest that there is a subset of dancers who have attitudes towards injury

that may cause them to continue to dance with pain and functional impairment. It is possible that

the experience of injury may lead a dancer to better understand injury and this may have an

impact on their perception of considering themselves injured or not injured. Although many

dancers who are modifying movement due to pain may consider themselves injured, the

preliminary findings of dancers’ attitudes towards injury, as well as the fact that 19.8% of

dancers who did not consider themselves injured had a SEFIP score of 3, bring light to the fact

that many dancers are dancing with pain as well as functional impairment without considering

themselves injured. There is some suggestion in the literature that these behaviors may lead to

chronic injury, although this has yet to be proven.14, 20 However, the high prevalence of reported

chronic injury in this group of professional dancers lends support to this theory. Education

regarding pain and injury is essential for these two subsets of dancers so they may be better able

to recognize when they are injured and seek the appropriate care. Qualitative research is needed

to better understand dancers’ attitudes and perceptions of pain and injury.

There is also some suggestion from the findings of this study that dancers may be using pain

medications (prescription and non-prescription) in order to continue to dance with pain which

may also have an impact on one’s attitudes towards pain and injury. This is especially worrisome

given the low prevalence of dancers under medical care for their dance-related pain. Studies of

elite Olympic athletes have demonstrated a dangerous overuse of non-steroidal anti-

inflammatory drugs (NSAIDs) as well as inappropriate use of concurrent multiple types of

NSAIDs and other medications.55 Gastrointestinal and central nervous system adverse effects

associated with NSAID use have been commonly reported in elite athletes.56 Additionally, there

is evidence from animal studies that the long term use of NSAIDs may actually inhibit protein

synthesis and therefore delay tissue healing.56 Further studies of pain medication use in

professional dancers are warranted, especially in Canada. Educational measures are urgently

needed for dancers regarding the appropriate use of pain medications and potential adverse

reactions.

4.3 Strengths and Limitations

This is the largest cross-sectional study of solely professional ballet and modern dancers to date

and one of the first international studies of professional dancers. I have focused on the point

92 prevalence of injury in these dancers in order to reduce recall bias. Additionally, I used

multivariable analysis to measure associated factors which has rarely been used in studies of

professional dancers. The response rate in this study was very good overall and I used a

comprehensive and psychometrically sound inventory of questions.

Care should be taken in interpreting factors associated with injury. As this is a cross-sectional

study, these should not be interpreted as risk factors. Confirmatory prospective studies should be

undertaken to ascertain if any of the associated factors are indeed risk factors for injury. In

addition, the odds ratios I report likely overestimate the reported associations since the outcomes

used in my models are not rare events.

Although, the results of this study are limited to the participating dance companies, they may be

generalizable to professional dancers in similar elite ballet companies. Caution should be taken

when attempting to generalize the results to dancers in other modern dance companies as it is

clear that modern dance companies are more heterogeneous than ballet companies. Caution

should also be taken when attempting to generalize to companies that do not operate on a full-

time basis (project based companies) or to freelance dancers. Although this is one of the largest

studies of professional dancers to date, modern dance companies are usually quite small in size

and this led to a lower number of modern dancers compared to ballet dancers in this study. Small

sample size may account for the difficulty in multivariable analysis in modern dancers. I strived

to obtain at least one modern and ballet company in each of the countries however the number of

larger modern companies in each country is limited and I was therefore unable to recruit a

modern dance company in Denmark. Additionally, I was unable to include a ballet company in

Israel.

Additionally, my sample was too small to attain sufficient power to perform multi-level

modeling to compare higher order factors such as country (societal) and dance company factors.

I was unable, therefore, to fully analyze company and country level data to determine its

association with injury in dancers. In addition to company and country level contextual data, it is

possible that other factors that I did not measure such as psychosocial/psychological factors may

play a role in injury in dancers. These factors have recently been explored in studies of Korean

dancers and should be studied in future studies of professional dancers in other countries. 31, 34

93 Following the instructions of the research ethics board, I could not contact or identify those

dancers who did not participate; therefore I do not have any information regarding these dancers.

It is possible that these dancers may have been injured. However, every attempt was made to

capture all dancers who were off work on the date of the survey distribution. These dancers were

mailed surveys in order to minimize any “healthy worker effect” in the results of this study. If

indeed a “healthy worker effect” came into play in this study, then the reported prevalence

estimates would be lower than the true estimate. This may have been the case with the lower

participation rate in the Kibbutz Contemporary Dance Companies and I have reported alternate

prevalence rates with the assumption that dancers who did not participate were injured. The true

estimates are likely somewhere between these two estimates.

It must also be stressed that in self-reported survey based cross-sectional studies, the potential for

misclassification of injury does exist. The self-reported injury outcome is injury from the

dancer’s perspective. The dancer was not given a specific definition of injury and no specific

diagnoses were made by health professionals. I have reported an alternate injury outcome, using

the SEFIP. Although this has been validated for use in dancers, no tool is perfect, and it is indeed

possible that misclassification of injury occurred using this outcome measure as well.

94

4.4 Future Directions

Due to the high prevalence of dance-related injury, further research is essential to investigate

possible interventions to help control injury and understand the long-term implications of injury

in professional dancers. Large prospective studies are needed to clearly identify risk factors that

are associated with injury in dancers. The use of an injury registry would allow researchers to

measure dance exposure and risk factors for injury providing important information for

professional dance companies. The associated factors identified in this study are only one piece

of the dance injury puzzle. Further research should focus on societal and company level factors

making use of multi-level modeling. Additionally, psychological and psychosocial factors and

their relationship with injury should be investigated in this population. Qualitative studies may

be used to further investigate dancers’ attitudes and perceptions of injury, identify barriers to

reporting injuries, and how best to make dancers feel less vulnerable when reporting their

injuries. Research into pain medication use in professional dancers and possible adverse effects

is warranted given the high prevalence of dancers using these medications.

95

Chapter 5: Conclusions

The prevalence of musculoskeletal pain and injury in professional ballet and modern dancers is

high. Professional ballet dancers suffer mostly from injuries to the lower limb and low back. The

types of injuries professional modern dancers suffer from vary among companies. The majority

of reported injuries are chronic in nature in both ballet and modern dancers. The results suggest

that modern dancers are less likely or able to take time off work due to injury. Soloist and

principal ballet dancers are more likely to be injured than corps de ballet dancers for self-

reported injury. Additionally, the number of years dancing professionally was positively

associated with injury in ballet dancers using a SEFIP score of ≥3 as the outcome.

The attitudes and perceptions towards injury vary in this population. Some dancers are

continuing to dance with pain and injury possibly as a result of these attitudes or fears of having

to stop dancing. This may potentially put these dancers at risk for further or greater injury.

Additionally, more than 15% of injured professional dancers are not reporting their injuries for a

variety of reasons including not wanting to have to stop dancing. Measures to support this subset

of injured professional dancers are necessary. Professional ballet and modern dancers are using

high levels of pain medications especially in Canada. Further research into dancers’ pain

medication use is essential. Large scale prospective studies are recommended to further

investigate risk factors for injury in professional dancers. Additionally qualitative studies are

recommended to further investigate dancers’ attitudes and perceptions of injury and how best to

support dancers afraid to report injury. Most importantly, there is an urgent need to investigate

interventions to help control injury and understand the long-term implications of these conditions

in this population.

95

96

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Appendix 1: Electronic Database Search Strategies

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103 Appendix 2: Study Questionnaire

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Appendix 3 : Research Ethics Board Approvals

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Professor Jan Hartvigsen Institut for Idræt og Biomekanik Syddansk Universitet Campusvej 55 5230 Odense M Sendt til: jhartvigsen@health.sdu.dk

Ovennævnte projekt er den 23. august 2007 anmeldt til Datatilsynet efter persondatalovens1 § 48, stk. 1. Der er samtidigt søgt om Datatilsynets tilladelse. Det fremgår af anmeldelsen, at De er dataansvarlig for projektets oplysninger. Behandlingen af oplysningerne ønskes påbegyndt snarest og forventes at ophøre 31. januar 2010. Oplysningerne vil blive behandlet på følgende adresse: Institut for Idræt og Biomekanik, Syddansk Universitet, Campusvej 55, 5230 Odense M. Oplysningerne vil endvidere blive behandlet ved det deltagende center: Toronto Western Hospital, 399 Bathurst Street, Felle Pavilion 4-114, Toronto, Ontario, Canada M5T 2S8.

5. november 2007 Vedrørende anmeldelse af: Perception of Musculoskeletal Injury in Professional Dancers

Datatilsynet Borgergade 28, 5. 1300 København K CVR-nr. 11-88-37-29 Telefon 3319 3200 Fax 3319 3218 E-post dt@datatilsynet.dk www.datatilsynet.dk J.nr. 2007-41-0979 Sagsbehandler Maiken Toftgaard Knudsen Direkte 3319 3248

TILLADELSE Datatilsynet meddeler hermed tilladelse til projektets gennemførelse, jf. persondatalovens § 50, stk. 1, nr. 1. Datatilsynet fastsætter i den forbindelse nedenstående vilkår: Generelle vilkår

1 Lov nr. 429 af 31. maj 2000 om behandling af personoplysninger med senere ændringer.

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Tilladelsen gælder indtil: 31. januar 2010 Ved tilladelsens udløb skal De særligt være opmærksom på følgende: Hvis De ikke inden denne dato har fået tilladelsen forlænget, går Datatilsynet ud fra, at projektet er afsluttet, og at personoplysningerne er slettet, anonymiseret, tilintetgjort eller overført til arkiv, jf. nedenstående vilkår vedrørende projektets afslutning. Anmeldelsen af Deres projekt fjernes derfor fra fortegnelsen over anmeldte behandlinger på Datatilsynets hjemmeside. Datatilsynet gør samtidig opmærksom på, at al behandling (herunder også opbevaring) af personoplysninger efter tilladelsens udløb er en overtrædelse af persondataloven, jf. § 70. 1. Professor Jan Hartvigsen er ansvarlig for overholdelsen af de fastsatte vilkår. 2. Oplysningerne må kun anvendes til brug for projektets gennemførelse. 3. Behandling af personoplysninger må kun foretages af den dataansvarlige eller på

foranledning af den dataansvarlige og på dennes ansvar. 4. Enhver, der foretager behandling af projektets oplysninger, skal være bekendt med de fastsatte

vilkår. 5. De fastsatte vilkår skal tillige iagttages ved behandling, der foretages af databehandler. 6. Lokaler, der benyttes til opbevaring og behandling af projektets oplysninger, skal være indrettet

med henblik på at forhindre uvedkommende adgang. 7. Behandling af oplysninger skal tilrettelægges således, at oplysningerne ikke hændeligt eller

ulovligt tilintetgøres, fortabes eller forringes. Der skal endvidere foretages den fornødne kontrol for at sikre, at der ikke behandles urigtige eller vildledende oplysninger. Urigtige eller vildledende oplysninger eller oplysninger, som er behandlet i strid med loven eller disse vilkår, skal berigtiges eller slettes.

8. Oplysninger må ikke opbevares på en måde, der giver mulighed for at identificere de

registrerede i et længere tidsrum end det, der er nødvendigt af hensyn til projektets gennemførelse.

9. En eventuel offentliggørelse af undersøgelsens resultater må ikke ske på en sådan måde, at

det er muligt at identificere enkeltpersoner. 10. Eventuelle vilkår, der fastsættes efter anden lovgivning, forudsættes overholdt.

Elektroniske oplysninger 11. Identifikationsoplysninger skal krypteres eller erstattes af et kodenummer el. lign. Alternativt

kan alle oplysninger lagres krypteret. Krypteringsnøgle, kodenøgle m.v. skal opbevares forsvarligt og adskilt fra personoplysningerne.

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12. Adgangen til projektdata må kun finde sted ved benyttelse af et fortroligt password. Password skal udskiftes mindst én gang om året, og når forholdene tilsiger det.

13. Ved overførsel af personhenførbare oplysninger via Internet eller andet eksternt netværk skal

der træffes de fornødne sikkerhedsforanstaltninger mod, at oplysningerne kommer til uvedkommendes kendskab. Oplysningerne skal som minimum være forsvarligt krypteret under hele transmissionen. Ved anvendelse af interne net skal det sikres, at uvedkommende ikke kan få adgang til oplysningerne.

14. Udtagelige lagringsmedier, sikkerhedskopier af data m.v. skal opbevares forsvarligt aflåst og

således, at uvedkommende ikke kan få adgang til oplysningerne. Manuelle oplysninger 15. Manuelt projektmateriale, udskrifter, fejl- og kontrollister, m.v., der direkte eller indirekte

kan henføres til bestemte personer, skal opbevares forsvarligt aflåst og på en sådan måde, at uvedkommende ikke kan gøre sig bekendt med indholdet.

Oplysningspligt over for den registrerede

16. Hvis der skal indsamles oplysninger hos den registrerede (ved interview, spørgeskema,

klinisk eller paraklinisk undersøgelse, behandling, observation m.v.) skal der uddeles/fremsendes nærmere information om projektet. Den registrerede skal heri oplyses om den dataansvarliges navn, formålet med projektet, at det er frivilligt at deltage, og at et samtykke til deltagelse til enhver tid kan trækkes tilbage. Hvis oplysningerne skal videregives til brug i anden videnskabelig eller statistisk sammenhæng, skal der også oplyses om formålet med videregivelsen samt modtagerens identitet.

17. Den registrerede bør endvidere oplyses om, at projektet er anmeldt til Datatilsynet efter

persondataloven, samt at Datatilsynet har fastsat nærmere vilkår for projektet til beskyttelse af den registreredes privatliv. Indsigtsret

18. Den registrerede har ikke krav på indsigt i de oplysninger, der behandles om den

pågældende.

Videregivelse 19. Videregivelse af personhenførbare oplysninger til tredjepart må kun ske til brug i andet

statistisk eller videnskabeligt øjemed.

20. Videregivelse må kun ske efter forudgående tilladelse fra Datatilsynet. Datatilsynet kan stille nærmere vilkår for videregivelsen samt for modtagerens behandling af oplysningerne. Ændringer i projektet

21. Væsentlige ændringer i projektet skal anmeldes til Datatilsynet (som ændring af eksisterende

anmeldelse). Ændringer af mindre væsentlig betydning kan meddeles Datatilsynet.

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22. Ændring af tidspunktet for projektets afslutning skal altid anmeldes.

Ved projektets afslutning

23. Senest ved projektets afslutning skal oplysningerne slettes, anonymiseres eller tilintetgøres,

således at det efterfølgende ikke er muligt at identificere enkeltpersoner, der indgår i undersøgelsen.

24. Alternativt kan oplysningerne overføres til videre opbevaring i Statens Arkiver (herunder Dansk Dataarkiv) efter arkivlovens regler.

25. Sletning af oplysninger fra elektroniske medier skal ske på en sådan måde, at oplysningerne

ikke kan genetableres. Overførsel af oplysninger til tredjelande

26. Overførsel af oplysninger til tredjelande, herunder til behandling hos databehandler samt til

intern anvendelse i projektet, kræver forudgående tilladelse fra Datatilsynet.

27. Overførsel kan dog ske uden tilladelse, hvis den registrerede har givet udtrykkeligt samtykke til dette. Den registrerede kan tilbagekalde samtykket.

28. Overførsel af oplysninger skal ske med bud eller anbefalet post. Ved elektronisk overførsel skal der træffes de fornødne sikkerhedsforanstaltninger mod, at oplysningerne kommer til uvedkommendes kendskab. Oplysningerne skal som minimum være forsvarligt krypteret under hele transmissionen.

Ovenstående vilkår er gældende indtil videre. Datatilsynet forbeholder sig ret til senere at tage vilkårene op til revision, hvis der skulle vise sig behov for det. Opmærksomheden henledes specielt på, at Datatilsynets vilkår også skal iagttages ved behandling af oplysninger på de deltagende centre mv., jf. de generelle vilkår nr. 4. Datatilsynet gør opmærksom på, at denne tilladelse alene er en tilladelse til at behandle personoplysninger i forbindelse med projektets gennemførelse. Tilladelsen indebærer således ikke en forpligtelse for myndigheder, virksomheder m.v. til at udlevere eventuelle oplysninger til Dem til brug for projektet. En videregivelse af oplysninger fra statistiske registre, videnskabelige projekter m.v. kræver dog, at den dataansvarlige har indhentet særlig tilladelse hertil fra Datatilsynet, jf. persondatalovens § 10, stk. 3. Anmeldelsen offentliggøres i fortegnelsen over anmeldte behandlinger på Datatilsynets hjemmeside www.datatilsynet.dk. Persondataloven kan læses/hentes på Datatilsynets hjemmeside under punktet "Lovgivning".

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Med venlig hilsen Maiken Toftgaard Knudsen

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Appendix 4: Copyright Acknowledgements The use of the Self-Estimated Functional Inability because of Pain (SEFIP) is with permission of

Dr. Eva Ramel.