Gluteus Maximus Preactivation Using

a Thera-Band Alters Gluteus Maximus

Muscle Activity and the Anterior Pelvic

Tilt Angle During Bridging Exercise

Silah Choi

The Graduate School

Yonsei University

Department of Physical Therapy

Gluteus Maximus Preactivation Using

a Thera-Band Alters Gluteus Maximus

Muscle Activity and the Anterior Pelvic

Tilt Angle During Bridging Exercise

Silah Choi

The Graduate School

Yonsei University

Department of Physical Therapy

Gluteus Maximus Preactivation Using

a Thera-Band Alters Gluteus Maximus

Muscle Activity and the Anterior Pelvic

Tilt Angle During Bridging Exercise

A Masters Thesis Submitted to the Department of Physical Therapy

and the Graduate School of Yonsei University in partial fulfillment of the requirements

for the degree of Master of Science

Silah Choi

December 2013

This certifies that the masters thesis of Silah Choi is approved.

Thesis Supervisor: Heonseock Cynn

Ohyun Kwon: Thesis Committee Member #1

Chunghwi Yi: Thesis Committee Member #2

The Graduate School Yonsei University

December 2013

Acknowledgements

First, I would like to express my gratitude to my supervisor, Professor Heonseock

Cynn. He continuously gave me confidence and always supported me. He devoted a

great deal of time to discussing and sharing opinions about my research. With his

assistance and encouragement, I was able to improve my research and expand my

knowledge. His inspiration exceeded the academic aspects of my life; he also taught

me to have a sense of responsibility and to consider principles and beliefs in order to

become a respectable person. I feel honored to have met him and I am delighted to

have been his student.

I would also like to thank my thesis committee members. Professor Chunghwi Yi

helped to improve the quality of my thesis with his detailed and insightful comments.

He always treated me with kindness and made me feel very comfortable in my school

life. Professor Ohyun Kwon offered me opportunities to obtain experience in the

clinical field and taught me practical skills and scientific methods. He also took the

time to listen to my vision for the future and provide sincere advice. He was

tremendous help in designing my future and furthering my self-development. I would

also like to express my deep appreciation to Professor Sanghyun Cho, Professor

Hyeseon Jeon, and Professor Sunghyun Yu for their thoughtfulness, encouragement,

and assistance during my master’s course.

I would like to thank all the members of the applied kinesiology and ergonomic

technology laboratory: Taelim Yoon, Jihyun Lee, Kyungmi Park, Woojeong Choi,

Changhee Ko, and Hyojeong Jung. In their kindness, they have been like sisters and

brothers to me, cheering me on, working together, and sharing discussions. Their

heartfelt advice and intellectual support encouraged me to complete my master’s

course. I would also like to express my gratitude to all members of the graduate

school, department of physical therapy, who were always kind and caring in daily

life—especially when I needed help with my research. I will have many happy

memories of Sungdae Choung, Onebin Lim, and Sunyoung Kang, who continuously

motivated me and helped me to adapt to school life from beginning to end.

Additionally, I want to thank all of my junior colleagues who participated in my

research, helped me to carry out data collection, and empathized with me.

Finally, I thank my family. They have shown me infinite love and support. It would

have been impossible for me to finish this work without my family. I promise to

reward you with good achievements. I love you very much. Although my grandfather

is no longer on this earth, he would have been very happy and proud of my

accomplishments. I miss you.

I could not have completed my thesis without the contribution and encouragement

of many people. I deeply appreciate all those who made this work possible. Please

know that I will continue to thirst for knowledge and develop my skills.

Thank you.

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Table of Contents

List of Figures ························································································ iii

List of Tables ························································································· iv

Abstract ·································································································· v

Introduction ····························································································· 1

Methods ·································································································· 4

1. Subjects ··························································································· 4

2. Instrumentation ················································································ 6

2.1 Surface Electromyography ························································· 6

3. Experimental Procedures ································································· 8

3.1 Bridging Without Isometric Hip Abduction ································ 9

3.2 Bridging With Isometric Hip Abduction ··································· 12

3.3 Measurement of Anterior Pelvic Tilt Angle ······························ 14

4. Statistical Analysis ········································································ 16

Results ·································································································· 17

1. Subjects ························································································· 17

2 Electromyographic Data ································································· 18

2.1 Gluteus Maximus, Hamstrings, and Erector Spinae Muscle Activity

···································································································· 18

2.2 Gluteus Maximus/Hamstrings and Gluteus Maximus/Erector Spinae

Muscle Activity Ratios ······························································· 20

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2.3 Anterior Pelvic Tilt Angle ·························································· 21

Discussion ····························································································· 23

Conclusion ···························································································· 29

References ···························································································· 30

Abstract in Korean ················································································ 38

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List of Figures

Figure 1. Starting position of bridging exercise ············································ 9

Figure 2. Bridging without isometric hip abduction ··································· 11

Figure 3. Bridging with isometric hip abduction using the Thera-Band ···· 13

Figure 4. Measurement of anterior pelvic tilt angle ·································· 15

Figure 5. Comparison of gluteus maximus muscle activity between bridging

exercise with and without isometric hip abduction ······················ 19

Figure 6. Comparison of anterior pelvic tilt angle between bridging exercise

with and without isometric hip abduction ··································· 22

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List of Tables

Table 1. General characteristics of subjects·············································· 17

Table 2. Comparison of muscle activity in the gluteus maximus, hamstrings,

and erector spinae between two conditions of bridging exercise

································································································ 18

Table 3. Comparison of gluteus maximus/hamstrings and gluteus maximus/

erector spinae ratios between g two conditions of bridging exercise

·································································································· 20

Table 4. Comparison of anterior pelvic tilt angle between two conditions of

bridging exercise ······································································· 21

-v-

ABSTRACT

Gluteus Maximus Preactivation Using a Thera-Band Alters

Muscle Activity and the Anterior Pelvic Tilt Angle

During Bridging Exercise

Silah Choi Dept. of Physical Therapy

The Graduate School

Yonsei University

The gluteus maximus (GM) is frequently weak and lengthened because many

people spend a great amount of time remaining seated. Hamstring (HAM) tightness

and excessive anterior pelvic tilt with dominant erector spinae (ES) can be observed

as a compensatory mechanism for a weak GM. The purpose of this study was to

investigate the effects of bridging with isometric hip abduction (IHA) using the

Thera-Band on GM, HAM, and ES muscle activity; GM/HAM and GM/ES ratios;

and the anterior pelvic tilt angle in healthy subjects. Twenty-one subjects participated

in this study and all subjects performed bridging with and without IHA. Surface EMG

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was used to collect EMG data of GM, HAM, and ES muscle activities, and Image J

software was used to measure anterior pelvic tilt angle. A paired t-test was used to

compare GM, HAM, and ES muscle activity; the GM/HAM and GM/ES ratios; and

the anterior pelvic tilt angle with and without IHA during the bridging exercise. GM

muscle activity increased significantly and the anterior pelvic tilt angle decreased

significantly during bridging with IHA using the Thera-Band (p < 0.05). However,

there were no significant differences in the activity of the HAM and ES and the

GM/HAM and GM/ES ratios between bridging with and without IHA (p > 0.05). The

results of this study suggest that bridging with IHA using the Thera-Band can be

implemented as an effective method to facilitate GM muscle activity and reduce the

anterior pelvic tilt angle.

Key words: Bridging, Gluteus maximus, Preactivation, Thera-Band.

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Introduction

The gluteus maximus (GM) is one of the largest and strongest muscles in the body.

The GM originates from the posterior sacrum and coccyx as well as the posterior

gluteal line of the ilium and inserts on the iliotibial tract and gluteal tuberosity of the

femur (Frank and Netter, 1987). The GM is a powerful extensor and external rotator

of the hip, and the superior part of the GM acts as a hip abductor because muscle

fibers in the GM are directed downward and outward (Frank and Netter, 1987; Long

et al., 1993). Hip extensors, especially the GM, are important for many functional

activities of daily living such as moving from sitting to standing, climbing stairs, and

maintaining an upright posture during walking (Winter, 1991). Because the direction

of the GM muscle fibers, especially deep sacral fibers of the GM, are perpendicular to

the sacroiliac (SI) joint, GM contraction improves SI joint stability and plays a part in

force transmission from the lower extremity to the pelvis during ambulation (Hossain

and Nokes, 2005; Leinonen et al., 2000; Mooney et al., 2001).

However, the GM is frequently weak and lengthened because many people spend a

great amount of time remaining seated (Sahrmann, 2002). Decreased activity of the

GM is one cause of low back pain (LBP) and results in SI joint instability and

dysfunction (van Wingerden et al., 2004). In addition, hamstring (HAM) tightness can

be observed as a compensatory mechanism for a weak GM (Massoud et al., 2011; van

Wingerden et al., 2004). Also, excessive anterior pelvic tilt, lumbar lordosis with

-2-

dominant erector spinae (ES), and lumbar rotation occur in place of a weak GM or

delayed GM activation during hip extension (Chaitow, 1996; Sahrmann, 2002).

There are various exercises to strengthen the hip extensors, including the squat,

lunge, and prone hip extension (Distefano et al., 2009; Kang et al., 2013; Wagner et

al., 2010). Among these exercises, bridging exercises are the most commonly used by

people with weak hip extensors and trunk muscles in physical therapy programs.

Bridging exercises are closed-chain weight-bearing exercises that support the body

weight against gravity. They activate the hip extensors and trunk muscles to a greater

extent than the abdominal muscles and are useful for lumbopelvic stabilization and

the control of pelvic motion (Ekstrom et al., 2007; Mori A, 2004; O'Sullivan and

Schimitz, 2007; Richardson, 1995). In addition, bridging exercises can be easily

modified and applied in diverse ways, including single-leg bridging, ball bridging,

and bridging with different knee positions (Ekstrom et al., 2008; Stevens et al., 2006).

However, bridging exercises are associated with a risk of dominant HAM and ES

activity and excessive anterior pelvic tilt as a compensation for GM weakness

regardless of the type of bridging exercise performed. Therefore, bridging exercise

with isometric hip abduction (IHA) using a Thera-Band (Hygenic Corp., Akron, OH,

USA) was devised in this study. The Thera-Band is a useful and portable clinical tool

for increasing strength, mobility, and function in multi-planar movements and various

part of the body (Mikesky et al., 1994; Selkowitz et al., 2013).

No previous studies have compared GM with HAM and ES muscle activity and

pelvic kinematics during bridging with IHA using the Thera-Band. Thus, the purpose

-3-

of this study was to investigate the effects of bridging with IHA using the Thera-Band

on GM, HAM, and ES muscle activity; GM/HAM and GM/ES ratios; and the anterior

pelvic tilt angle in healthy subjects. It was hypothesized that bridging with IHA using

the Thera-Band would result in increased GM muscle activity, increased GM/HAM

and GM/ES ratios, and a decreased anterior pelvic tilt angle.

-4-

Methods

1. Subjects

Prior to recruiting subjects for this study, a power analysis was performed with

G*power software ver. 3.1.2 (Franz Faul, University of Kiel, Kiel, Germany) using

the results of a pilot study involving five subjects. The calculation of sample size was

carried out with a power of 0.80, alpha level of 0.05, and effect size of 0.89. This

provided a necessary sample size of ten subjects for this study.

Twenty-one healthy subjects were recruited from a university population. The

exclusion criteria were: (1) limitations in range of motion of the bilateral hip, knee,

and ankle joints; (2) a history of LBP or lower extremity dysfunctions such as

iliotibial band friction syndrome, patellofemoral pain syndrome, anterior cruciate

ligament sprains, or chronic ankle instability (Cichanowski et al., 2007; Fredericson

et al., 2000; Friel et al., 2006; Hewett et al., 2006; Ireland et al., 2003) in the past 12

months; (3) iliopsoas, rectus femoris, or tensor fasciae latae tightness as evidenced by

the Thomas test, Ely’s test, or modified Ober’s test, respectively (Kendall, 2005;

Magee, 2007); and (4) lumbopelvic instability demonstrated by performing the active

straight leg raising test with a pressure biofeedback unit (Liebenson, 2004; Mens et al.,

1999).

-5-

Prior to collecting data, the examiner informed the subjects of the study procedures

and each subject completed an informed consent form. The study protocol was

approved by the Yonsei University Wonju Institutional Review Board.

-6-

2. Instrumentation

2.1 Surface Electromyography

Electromyographic (EMG) data were collected using a TeleMyo DTS (Noraxon

Inc., Scottsdale, AZ, USA) and analyzed using MyoResearch 1.08 XP software

(Noraxon Inc.). The electrode sites were shaved and then rubbing alcohol was used to

reduce skin impedance. Two surface electrodes were positioned at an interelectrode

distance of 2㎝ bilaterally.

EMG data were collected for the GM, HAM, and ES. The upper fibers of the GM

represented the GM in this study. The electrode for the GM was placed half the

distance between the trochanter and sacral vertebrae in the middle of the muscle at an

oblique angle at the level of the trochanter. For general recordings of the HAM, the

electrode for the HAM was placed parallel to the muscle in the center of the back of

the thigh, approximately half the distance from the gluteal fold to the back of the knee.

The electrode for the ES was placed parallel to the spine at the level of the iliac crest,

approximately 2 ㎝ apart from the spine over the muscle mass (Criswell, 2010).

EMG signals were sampled at 1000㎐. Notch filter was preset to reject 60㎐. A band

pass filter was used between 20 and 450 ㎐. The raw data were processed into the

root mean square (RMS) with a window of 50㎳.

Normalization was needed to minimize variables or differences between different

recoding sites and individuals. The maximal voluntary isometric contraction (MVIC)

-7-

normalization method was applied to each tested muscle and MVIC was recorded

during a manual muscle test (MMT) in the positions described by Kendall et al.

(2005). To collect MVIC data, subjects maintained the MMT position of each tested

muscle against manual resistance for 5 s. The middle 3-s contraction, excluding each

1 s at the beginning and end, was used for data analysis, and a 30-s rest was given

between the two trials. The mean value of the two trials for the maximal contraction

in each muscle was taken as the MVIC. All EMG data collected were expressed as an

RMS-processed percentage of the MVIC (%MVIC).

-8-

3. Experimental Procedures

Subjects were informed of the standardized position of the bridging exercise in this

study and underwent a familiarization period of approximately 20 min to achieve a

proper exercise performance capability. When subjects failed to perform the

standardized position and maintain the position during the exercise period, data

collection was immediately stopped. Bridging without IHA was followed by bridging

with IHA to minimize the learning effect. The mean value of two trials of each

bridging exercise was used for data analysis. A 5-min rest between the two conditions

and a 1-min rest between every two trials was given to avoid muscle fatigue.

-9-

3.1 Bridging Without Isometric Hip Abduction

The subjects were placed in a supine position. Both knees were flexed at 90°, the

feet were hip-width apart while resting on the floor, and the toes were facing forward.

The arms were crossed over the chest to minimize arm support (Figure 1).

Figure 1. Starting position of bridging exercise.

-10-

Two plastic poles were placed vertically along the lateral aspect of the bilateral knee

joint to maintain hip abduction of 30°. A wooden target bar was placed at the height

of the middle point of the thigh between the greater trochanter and femoral condyle

when the trunk, pelvis, and thigh were aligned in a straight line (hip extension of 0°).

A universal goniometer was used for knee and hip angle measurements. The subject

was instructed to lift his pelvis comfortably at a self-selected speed while maintaining

contact between the lateral aspects of the bilateral knee joint and vertically placed

plastic poles. When both thighs touched the wooden target bar during bridging, the

subject was asked not to lift his pelvis further and to hold the bridging position for 5 s

without pelvic or thigh movement. After 5 s of bridging, the subject lowered his

pelvis (Figure 2).

-11-

Figure 2. Bridging without isometric hip abduction.

-12-

3.2 Bridging With Isometric Hip Abduction

Bridging with IHA followed the same procedure as bridging without IHA, with the

exception of the application of a blue-colored Thera-Band, which is recommended by

the manufacturer for an intermediate or advanced workout level. The Thera-Band was

wrapped around both thighs just proximal to the knees, providing consistent

resistance to IHA. Tension was controlled by lengthening or shortening the Thera-

Band. The tension in the Thera-Band was determined when the subject was able to

perform more than ten repetitions of hip abduction of 30° in hook-lying position

using the Thera-Band (Decker et al., 1999; Park et al., 2013) (Figure 3).

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Figure 3.Bridging with isometric hip abduction using the Thera-Band.

-14-

3.3 Measurement of Anterior Pelvic Tilt Angle

To obtain pelvic kinematic data, two reflective markers were placed on specific

anatomical landmarks; namely, the anterior superior iliac spine (ASIS) and posterior

superior iliac spine (PSIS). In this study, the anterior pelvic tilt was defined as an

angle between a line joining the ASIS, PSIS, and the vertical line from the ASIS

(Figure 4). The examiner took a picture of the subject’s pelvis with a digital camera

when the subject maintained the position under two conditions of bridging exercises.

The location of the digital camera and distance from the digital camera to the subject

were consistent. These pictures were then transferred to Image J software (National

Institutes of Health, Bethesda, MD, USA) and used to measure the anterior pelvic tilt

angle.

-15-

Figure 4. Measurement of anterior pelvic tilt angle.

-16-

4. Statistical Analysis

A Kolmogorov-Smirnov Z-test was performed to confirm a normal distribution. A

paired t-test was used to compare GM, HAM, and ES muscle activity; the GM/HAM

and GM/ES ratios; and the anterior pelvic tilt angle with and without IHA during the

bridging exercise. Statistical significance was set at 0.05. All statistical analyses were

performed using PASW Statistics ver. 18.0 (SPSS, Inc., Chicago, IL, USA).

-17-

Results

1. Subjects

The general characteristics of the 21 subjects, including age, height, weight, and

body mass index, are shown in Table 1.

Table 1.General characteristics of subjects (N=21)

Parameters Mean±SD

Age (years) 22.5 ± 1.0

Height (㎝) 165.3 ± 7.1

Weight (㎏) 57.5 ± 8.7

BMIa (㎏/㎡) 20.9 ± 1.8 aBMI: Body mass index.

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2. Electromyographic Data

All dependent variables were found to approximate a normal distribution

(Kolmogorov-Smirnov Z-test, p > 0.05).

2.1 Gluteus Maximus, Hamstrings, and Erector Spinae Muscle Activity

In terms of muscle activity, GM muscle activity increased significantly during

bridging with IHA using the Thera-Band (p < 0.05) (Figure 5). However, there were

no significant differences in the activity of the HAM and ES (p > 0.05) between

bridging with and without IHA (Table 2).

Table 2. Comparison of muscle activity in the gluteus maximus, hamstrings, and

erector spinae between two conditions of bridging exercise (N=21)

Muscles Bridging without IHAa Bridging with IHA t p

GMb 21.06 ± 12.16e 25.50 ± 13.01 -3.016 0.007

HAMc 37.96 ± 16.89 42.97 ± 20.22 -2.040 0.055

ESd 52.93 ± 4.23 54.18 ± 4.01 -0.565 0.578 aIHA: Isometric hip abduction. bGM: Gluteusmaximus. cHAM: Hamstrings. dES: Erectorspinae. eMean ±Standard deviation of % maximal voluntary isometric contraction.

-19-

Figure 5. Comparison of gluteus maximus muscle activity between bridging exercise

with and without isometric hip abduction.

IHA: Isometric hip abduction.

* p < 0.05.

-20-

2.2 Gluteus Maximus/Hamstrings and Gluteus Maximus/Erector Spinae Muscle Activity Ratios

In terms of muscle ratios, the GM/HAM and GM/ES ratios were not significantly

different between bridging with and without IHA (p > 0.05) (Table 3).

Table 3. Comparison of gluteus maximus/hamstrings and gluteus maximus/erector

spinae ratios between g two conditions of bridging exercise (N=21)

Ratio Bridging without IHAa Bridging with IHA t p

GM/HAMb 0.72 ± 0.67d 0.73 ± 0.52 -0.119 0.906

GM/ESc 0.45 ± 0.34 0.49 ± 0.23 -0.748 0.463 aIHA: Isometric hip abduction. bGM/HAM: Gluteus maximus/hamstrings. cGM/ES: Gluteus maximus/erector spinae. dMean ± Standard deviation.

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2.3 Anterior Pelvic Tilt Angle

With regard to pelvic kinematics, the anterior pelvic tilt angle decreased

significantly during bridging with IHA using the Thera-Band (p < 0.05) (Table 4)

(Figure 6).

Table 4. Comparison of anterior pelvic tilt angle between two conditions of bridging

exercise (N=21)

Pelvic Kinematics Bridging without IHAa Bridging with IHA t p

Anterior pelvic

tilt angle 7.65 ± 2.36b 6.08 ± 2.28 3.055 0.006

aIHA: Isometric hip abduction. bMean ± Standard deviation (°)

-22-

Figure 6. Comparison of anterior pelvic tilt angle between bridging exercise with and

without isometric hip abduction.

IHA: Isometric hip abduction.

* p < 0.05.

-23-

Discussion

The aim of this study was to determine whether GM, HAM, and ES muscle

activity; the GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle could be

altered when IHA using the Thera-Band was applied during bridging in healthy

subjects. To my knowledge, this study is the first to evaluate the effect of IHA with

the Thera-Band on GM muscle preactivation and pelvic kinematics during a bridging

exercise. The results partially supported the research hypothesis.

GM activity increased significantly by 21.1% during bridging with IHA using the

Thera-Band, supporting the research hypothesis. A possible explanation is that

applying IHA with the Thera-Band during bridging and maintaining hip abduction of

30° induced preactivation of the GM before initiation of the bridging movement,

consequently increasing GM muscle activity. Isometric exercises have been used to

develop static muscle strength or muscular endurance and facilitate muscle firing to

reestablish neuromuscular control (Kisner and Cloby, 2007). Our present finding is in

agreement with those of previous studies demonstrating the effect of muscle

preactivation on muscle firing or force. Linnamo et al. (2003) investigated motor unit

activation patterns in concentric and eccentric contractions with and without isometric

preactivation at different force levels. At the highest force level, when movement was

initiated with preactivation, the mean spike amplitude in concentric contraction was

higher than that in eccentric contraction, while no significant difference in mean spike

amplitude was shown between concentric and eccentric contractions during

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movement without preactivation. Kyrolaïnen et al. (1999) emphasized the importance

of the preactivation of leg extensor muscles for increasing running speed. Specifically,

this finding determined that preactivity of the gastrocnemius muscle functioned as a

preparatory requirement to enhance muscle activity and the timing of muscular action

with respect to ground contact during the running cycle. Mrdakovic et al. (2008)

confirmed that when a knee extensor bench exercise was performed before (or

preceded by) a leg press exercise by means of muscle preactivation, an increased

EMG signal was recorded from the vastus lateralis muscle. This result indicates that

preactivation performance by a single-joint exercise increases the number of motor

units recruited during a multi-joint exercise.

The GM is quadrilateral in shape, and its fibers are obliquely directed inferiorly

and laterally. It functions not only as a hip extensor, but also as a hip abductor and

external rotator (Frank and Netter, 1987; McAndrew et al., 2006). In this study, hip

abduction of 30° was sustained by two plastic poles placed vertically along the lateral

aspect of the bilateral knee joints. Such hip abduction during bridging might facilitate

GM activity in terms of the action of the GM as a hip abductor and external rotator. In

a previous study, Kang et al. (2013) reported that the GM EMG amplitude was

greatest at 30° of hip abduction during prone hip extension with knee flexion.

Because the GM is a fusiform muscle that is optimized when the direction of muscle

pull is parallel to the muscle fiber, hip abduction during prone hip extension with

knee flexion leads to an increased EMG amplitude of the GM.

-25-

It was expected that HAM and ES activity would be reduced when GM activity

was increased by applying IHA with the Thera-Band during bridging exercise. This

hypothesis was based on the findings of previous studies demonstrating that

synergistic muscles work together to perform the same range of motion. For example,

increased or decreased changes in the activity of one muscle can lead to opposing

changes in activity of another synergistic muscle (Jonkers et al., 2003; Kang et al.,

2013; Park et al., 2013). Based on these findings, synergistic muscles during bridging

(i.e., trunk extensors such as the GM, HAM, and ES) can affect one another during

bridging: increased GM activity could reduce HAM and ES activity. However, the

present study also produced findings that are inconsistent with the hypothesis.

Although GM activity was significantly increased, it failed to elicit changes in the

GM/HAM and GM/ES ratios. The GM/HAM and GM/ES ratios did not reach

statistical significance between bridging with and without IHA.

The unexpected findings in this study may be the result of several differences from

previous studies. First, in contrast to the subjects in previous studies, healthy subjects

participated in the present study and exhibited HAM or ES activity that was dominant

to (or greater than) the GM activity at the beginning of the study. In many previous

studies that investigated GM activity during various bridging or prone hip extension

exercises in healthy subjects, the mean activity levels of the ES and HAM at baseline

(i.e., before the intervention) were less than or similar to the mean value for the GM

(Ekstrom et al., 2007; Ekstrom et al., 2008; Kang et al., 2013; Sakamoto et al., 2009).

However, in this study, especially for the ES, the mean value of ES activity was twice

-26-

the mean value reported previously (García-Vaquero et al., 2012; Imai et al., 2010;

Lehman et al., 2005; Okubo et al., 2010). In addition, because the mean value of

HAM and ES muscle activity was about 1.8 and 2.5 times that of the GM,

respectively, during bridging without IHA in this study (without intervention or at

entry), bridging with IHA would not likely lead to significant decreases in the

dominant HAM and ES in a cross-sectional study.

Second, because a wooden target bar was used to control pelvic lift during bridging,

increased activation of the HAM and ES was not likely to occur in the present study.

No previous studies have recommended the most appropriate level of pelvic lifting

during bridging, and over-lifting the lumbopelvis during bridging can be

disadvantageous due to potential overactivation of the already-dominant HAM and

ES; thus, a wooden target bar was placed to provide contact, cueing the subjects not

to over-lift the pelvis while performing the two types of bridging. However, this valid

use of a wooden target bar could have limited the level of the lumbopelvis and

consequently might have prevented overactivation of the HAM and ES during

bridging. Thus, HAM and ES activity may have differed if the subjects had performed

bridging without a wooden target bar.

The anterior pelvic tilt angle decreased significantly by 20.5% during bridging with

IHA using the Thera-Band, supporting the research hypothesis. Although the change

of anterior pelvic tilt angle was small, it could be a meaningful result in consideration

of measurement position because anterior pelvic tilt was measured in bridging

position in this study. Lembeck et al. (2005) reported that average pelvic tilt angle in

-27-

the lying position was lower than standing position. Thus, bridging with IHA using a

Thera-Band resulted in preactivation of the GM, and the increased GM activity could

have contributed to reduce anterior pelvic tilt. In other words, when the femur was

fixed, such as bridging position, contraction of the GM induced the pelvis to move

posteriorly and decrease anterior pelvic tilt and lumbar lordosis. Many previous

studies have emphasized that an important function of the GM is to maintain pelvic

stability. Oh et al. (2007) suggested that performance of the abdominal drawing-in

maneuver during prone hip extension encouraged activation of the hip extensors

while decreasing activation of the ES and reducing the anterior pelvic tilt. They

explained that increased GM muscle activity could be affected by biomechanical

alterations such as a reduced anterior pelvic tilt. Tateuchi et al. (2012) focused on

improvements in hip muscle balance between agonists and antagonists, which could

reduce the anterior pelvic tilt. An altered balance in muscle activation, especially a

hip flexor (tensor fasciae latae) dominant to the hip extensors (GM and

semitendinosus), during prone hip extension resulted in abnormal movement patterns,

such as anterior pelvic tilt and excessive lumbar extension.

The present study has several limitations. First, measurement errors were likely to

have occurred when measuring the pelvic kinematics because this study used only

two-dimensional image processing software. A three-dimensional motion analysis

system or real-time measuring system will be needed to improve the precision of

measurement in future studies. Second, the findings of this study are difficult to

generalize to the entire patient population because only healthy and young subjects

-28-

participated. Subjects with a broad age range and clinical symptoms such as GM

weakness should be investigated in future to strengthen the clinical implications of

this study. Finally, this study used a cross-sectional design and could not identify the

long-term effects of preactivation of the GM on HAM and ES activity. Future

longitudinal studies are necessary to show distinct differences in GM, HAM, and ES

muscle activity and anterior pelvic tilt angle.

-29-

Conclusion

This study investigated the effects of bridging with IHA using a Thera-Band on

GM, HAM, and ES activity; the GM/HAM and ES ratios; and the anterior pelvic tilt

angle. GM muscle activity increased significantly and the anterior pelvic tilt angle

decreased significantly during bridging with IHA using a Thera-Band. These findings

indicate that the application of a Thera-Band preactivates the GM before the initiation

of bridging, enhances GM activity, and prevents excessive anterior pelvic tilt during

bridging. Therefore, bridging with IHA using the Thera-Band can be implemented as

an effective method to facilitate GM muscle activity and reduce the anterior pelvic tilt

angle.

-30-

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국문 요약

교각운동 시 세라밴드를 이용한 대둔근의 전활성화가

대둔근의 근활성도와 골반의 전방경사

각도에 미치는 영향

연세대학교 대학원

물리치료학과

최 슬 아

대둔근은 많은 사람들이 상당한 시간을 앉아서 생활하면서 쉽게

약화되고 늘어나게 된다. 약화된 대둔근에 대한 보상작용으로 슬괵근의

단축, 우세한 척추기립근과 함께 나타나는 과도한 골반의 전방경사가 관찰

되기도 한다. 따라서 본 연구의 목적은 교각운동 시 세라밴드를 이용한

등척성 고관절 외전이 대둔근, 슬괵근, 척추기립근의 근활성도와

대둔근/슬괵근, 대둔근/척추기립근의 근활성비, 그리고 골반의 전방경사

각도에 미치는 영향을 알아보는 것이다. 본 연구를 위해 21명의 건강한

-39-

대상자가 참여하였고 모든 대상자는 세라밴드를 이용하여 등척성 고관절

외전을 적용한 교각운동과 그렇지 않은 교각운동을 실시하였다. 대둔근,

슬괵근, 척추기립근의 근활성도 자료를 수집하기 위해 표면 근전도를

사용하였고, 골반의 전방경사 각도는 이미지 제이 소프트웨어를 이용하여

측정하였다. 대둔근, 슬괵근, 척추기립근의 근활성도와 대둔근/슬괵근,

대둔근/척추기립근 근활성비, 그리고 골반의 전방경사 각도를 등척성

고관절 외전을 적용한 교각운동과 그렇지 않은 교각운동에서 비교하기

위해 짝비교 t-검정을 하였다.

세라밴드를 이용하여 등척성 고관절 외전을 적용한 교각운동에서

대둔근의 근활성도는 유의하게 증가하였고 골반의 전방경사 각도는

유의하게 감소하였다. 하지만 슬괵근, 척추기립근의 근활성도와

대둔근/슬괵근, 대둔근/척추기립근의 근활성비에서는 유의한 차이를

보이지 않았다. 본 연구의 결과를 바탕으로, 교각운동 시 세라밴드를

이용한 등척성 고관절 외전이 대둔근의 근활성도를 증진시키고 골반의

전방경사 각도를 감소시키는 데 효과적인 방법이 될 수 있음을 시사한다.

핵심 되는 말: 교각운동, 대둔근, 전활성화, 세라밴드.