Nicol van DykRehabilitation Department9 April 2016

INTER-SEASON VARIABILITY IN

ISOKINETIC STRENGTH ELITE FOOTBALL

Contributing Authors– Rod Whiteley– Cristiano Eirale– Bhavesh Kumar– Bruce Hamilton– Hans Tol– Aziz Farooq– Roald Bahr– Erik Witvrouw

Introduction

Odds Ratio p-value 95% CI

Q Con 60 0.99 0.06 0.99 - 1.00

H Con 60 0.99 0.17 0.99 - 1.00

Q Con 300 0.99 0.97 0.99 - 1.00

H Con 300 0.99 0.20 0.99 - 1.00

H Ecc 60 0.99 0.12 0.99 - 1.00

Q Con 60 BW 0.71 0.03* 0.52 - 0.97

H Con 60 BW 0.75 0.29 0.43 -1.29

Q Con 300BW 1.10 0.87 0.56 - 1.89

H Con 300 BW 0.75 0.29 0.43 - 1.29

H Ecc 60 BW 0.73 0.04* 0.54 - 0.99

Q Con 60/ H Con 60 0.76 0.32 0.44 - 1.32

H Con 60/ H Ecc 60 1.08 0.90 0.34 - 3.40

Q Con 300/ H Con 300 1.46 0.26 0.76 - 2.79

Q Con 300/ H Ecc 60 1.46 0.35 0.66 - 3.25

Q Con 60 BW 0.71 0.03* 0.52 - 0.97

H Ecc 60 BW 0.73 0.04* 0.54 - 0.99

Q Con 60 BW Effect Size

0.17 6.9 Nm

H Ecc 60 BW Effect Size

0.18 7.1 Nm

4 seasons

614 players

190 injuries

1931Isokinetic

Tests performed are WEAK risk factors

HAMSTRING STRAIN INJURIES

have a small association with

Odds Ratio p-value 95% CI

Q Con 60 0.99 0.06 0.99 - 1.00

H Con 60 0.99 0.17 0.99 - 1.00

Q Con 300 0.99 0.97 0.99 - 1.00

H Con 300 0.99 0.20 0.99 - 1.00

H Ecc 60 0.99 0.12 0.99 - 1.00

Q Con 60 BW 0.71 0.03* 0.52 - 0.97

H Con 60 BW 0.75 0.29 0.43 -1.29

Q Con 300BW 1.10 0.87 0.56 - 1.89

H Con 300 BW 0.75 0.29 0.43 - 1.29

H Ecc 60 BW 0.73 0.04* 0.54 - 0.99

Q Con 60/ H Con 60 0.76 0.32 0.44 - 1.32

H Con 60/ H Ecc 60 1.08 0.90 0.34 - 3.40

Q Con 300/ H Con 300 1.46 0.26 0.76 - 2.79

Q Con 300/ H Ecc 60 1.46 0.35 0.66 - 3.25

Q Con 60 BW 0.71 0.03* 0.52 - 0.97

H Ecc 60 BW 0.73 0.04* 0.54 - 0.99

Q Con 60 BW Effect Size

0.17 6.9 Nm

H Ecc 60 BW Effect Size

0.18 7.1 Nm

4 seasons

614 players

190 injuries

1931Isokinetic

Tests performed

Quadriceps Concentric strength

Hamstrings Eccentric strength

are WEAK risk factors HAMSTRING STRAIN INJURIES

Aim

How stable is the strength variable

we are testing?

All Teams in Qatar Stars

League (n=14 teams)

2010-2014

No isokinetic tests performed

(n=52 subjects)

Isokinetic Tests during Periodic Health Evaluation

(n=614 subjects) mean follow up of 2.24 years

Q Con 60°/s(n= 556)

H Con 60°/s(n= 555)

Q Con 300°/s(n= 556)

H Con 300°/s(n=556)

H Ecc 60°/s(n=562)

Materials & Methods

Over 1 season

240 players

Over 2 seasons

86 players

Over 3 seasons

18 players

Consecutive Isokinetic Strength Tests

Statistical Analyses

Systematic Error• Mean difference• Paired sample

t-tests

Random Error• Intraclass

Correlation Coeficient (ICC)

• Measurement Error

Statistical Analyses

Systematic Error• Mean difference• Paired sample

t-tests

Random Error• Intraclass

Correlation Coeficient (ICC)

• Measurement Error

Measurement Error

Standard Deviation (Season 1 – Season 2)

Quadriceps Concentric @60°/s

Hamstrings Eccentric @60°/s

Quadriceps Concentric strength

Measurement error

24.5 Nm (10.5%)

Mean (SD)

234.1 Nm (37.0)

ICC (95% CI)

0.82 (0.78,0.85)

Minimal detectable change (MDC)

67.9 Nm

Results

Measurement error26.6 Nm (14.6%)

Hamstrings Eccentric strength

Results

Mean (SD)

181.7 Nm (37.0)

Min detectable change (MDC)

73.7 Nm

ICC (95% CI)

0.68 (0.61,0.73)

Results

• 1st study to investigate stability/variability

• Large sample group over multiple seasons

• Different measures of variability tested

• No measure of exposure– Intervention/injury

Strengths and Limitations

Clinical Take Home Message

Substantial Isokinetic Inter-season Variability

• When testing strength…

Be careful interpreting isokinetic strength

NO

YES

MAYBE

• ?

Thank you