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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