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Muscle Imbalances: Testing and Training Functional Eccentric Hamstring Strength in Athletic Populations
Published on: May 1, 2018
Rate of torque and electromyographic development during anticipated eccentric contraction is lower in previously
David A Opar1, Morgan D Williams, Ryan G Timmins
1School of Exercise and Nutrition Science, Queensland University of Technology, Brisbane, Australia. d.opar@qut.edu.au
The American Journal of Sports Medicine
|October 31, 2012
Summary
Recreational athletes with previous hamstring injuries show reduced muscle activity and torque in the injured leg during eccentric contractions. This may hinder rehabilitation effectiveness and increase reinjury risk.
Area of Science:
- Sports Medicine
- Biomechanics
- Neuromuscular Physiology
Background:
- Limited research exists on how prior hamstring strain injuries impact muscle activation during high-torque tasks.
- Understanding these effects is crucial for effective rehabilitation and preventing re-injury in athletes.
Purpose of the Study:
- To investigate if recreational athletes with a history of unilateral hamstring strain injury exhibit reduced myoelectrical activity and torque development in the previously injured limb.
- To compare rate of torque development (RTD) and impulse (IMP) at specific time points (30, 50, 100 ms) post-contraction onset between injured and uninjured limbs.
Main Methods:
- A case-control study involving 26 recreational athletes (13 with prior unilateral hamstring strain, 13 controls).
- Isokinetic dynamometry and surface electromyography (iEMG) of biceps femoris long head and medial hamstrings during eccentric contractions (-60 and -180 deg·s⁻¹).
- Comparison of RTD, IMP, and iEMG between injured and uninjured limbs in the affected group.
Main Results:
- The injured limb showed significantly lower RTD and IMP at 50 and 100 ms during slow eccentric contractions (-60 deg·s⁻¹) compared to the uninjured limb.
- Lower biceps femoris long head myoelectrical activity (iEMG) was observed at 100 ms for both contraction speeds in the previously injured limb.
- No significant differences in medial hamstring activation or between-limb comparisons in the control group were found.
Conclusions:
- Previous hamstring injuries are associated with reduced torque production and biceps femoris long head activation during eccentric contractions.
- These neuromuscular deficits may impede rehabilitation progress and increase the risk of recurrent hamstring injuries.
- Rehabilitation programs should consider addressing neural function and enhancing myoelectrical activity in knee flexors post-injury.
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