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Effect of fatigue on hamstring coactivation during isokinetic knee extensions
J P Weir1, D A Keefe, J F Eaton
1Program in Physical Therapy, University of Osteopathic Medicine and Health Sciences, Des Moines, IA 50312, USA.
European Journal of Applied Physiology and Occupational Physiology
|December 5, 1998
Summary
Muscle fatigue increases hamstring muscle coactivation during knee extensions. This effect is consistent across different contraction speeds, indicating fatigue
Area of Science:
- Biomechanics
- Exercise Physiology
- Neuromuscular Control
Background:
- Quadriceps fatigue can alter knee joint stability.
- Hamstring coactivation plays a crucial role in protecting the knee joint.
Purpose of the Study:
- To investigate the impact of quadriceps fatigue on hamstring muscle coactivation.
- To determine if isokinetic contraction velocity influences this response.
Main Methods:
- Electromyography (EMG) recorded from vastus lateralis and biceps femoris muscles.
- Ten males and ten females performed maximal knee extensions at two isokinetic speeds (1.75 and 4.36 rad x s(-1)).
- Fatigue was induced over 50 repetitions per speed.
Main Results:
- Hamstring coactivation increased with quadriceps fatigue at both tested speeds.
- Higher coactivation levels were observed at the faster isokinetic speed (4.36 rad x s(-1)).
- The rate of coactivation increase during fatigue was independent of contraction velocity.
Conclusions:
- Quadriceps fatigue enhances hamstring coactivation, a protective mechanism.
- Contraction velocity influences the magnitude of coactivation but not the fatigue-induced rate of increase.
- Findings suggest fatigue-induced changes in neuromuscular control are velocity-independent.