Isokinetic strength tests are often used in risk factor analyses and Return to play decision making. However, there may be a large amount of variability within these measures. We share our results from the Rehabilitation Department at Aspetar in these slides.

1. Nicol van Dyk
Rehabilitation Department
9 April 2016
INTER-SEASON VARIABILITY
IN
ISOKINETIC STRENGTH
ELITE FOOTBALL

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

4. Introduction

5. 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
1931
Isokinetic
Tests
performed are WEAK risk factors
HAMSTRING STRAIN INJURIES
have a small association with

6. 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
1931
Isokinetic
Tests
performed
Quadriceps Concentric strength
Hamstrings Eccentric strength
are WEAK risk factors
HAMSTRING STRAIN INJURIES

7. Aim

8. 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
240players
Over 2 seasons
86players
Over 3 seasons
18players
Consecutive Isokinetic Strength Tests

9. Statistical Analyses
Systematic Error
• Mean difference
• Paired sample
t-tests
Random Error
• Intraclass
Correlation
Coeficient (ICC)
• Measurement Error

10. 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)

11. 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

12. Measurement error
26.6 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)

13. Results

14. • 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

15. Clinical Take Home Message
Substantial Isokinetic
Inter-season Variability
• When testing strength…
Be careful interpreting
isokinetic strength
NO
YES
MAYBE
• ?

17. Thank you