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Mechanisms contributing to knee extensor strength loss after prolonged running exercise.
G Y Millet1, V Martin, G Lattier
1INSERM/ERIT-M 0207 Motricité-Plasticité, Faculté des Sciences du Sport, Université de Bourgogne, 21078 Dijon Cedex, France. gmillet@u-bourgogne.fr
Journal of Applied Physiology (Bethesda, Md. : 1985)
|October 23, 2002
Summary
Prolonged running significantly reduces knee extensor strength due to central fatigue and neuromuscular factors. Greater strength loss in runners is linked to reduced voluntary activation.
Area of Science:
- Exercise Physiology
- Sports Science
- Neuromuscular Function
Background:
- Muscle strength decline after endurance exercise is a common issue for athletes.
- Understanding the underlying mechanisms is crucial for optimizing training and recovery.
Purpose of the Study:
- To investigate the neuromuscular mechanisms contributing to knee extensor strength loss after prolonged running.
- To identify factors associated with greater strength decrements in trained runners.
Main Methods:
- Maximal voluntary contraction (MVC) and superimposed twitches to assess voluntary activation (%VA).
- Percutaneous electrical stimulation of the femoral nerve (single twitch, 0.5-s tetanus at 20 and 80 Hz).
- Electromyogram (EMG) of the vastus lateralis recorded during stimulation and MVC.
Main Results:
- Knee extensor MVC decreased by 23.5% post-exercise (P < 0.001).
- Voluntary activation (%VA) also significantly reduced post-exercise (P < 0.05).
- Strength loss and activation deficit were highly correlated (R = 0.88, P < 0.001).
Conclusions:
- Central fatigue, neuromuscular propagation, and muscular factors contribute to strength loss after prolonged running.
- Runners experiencing the largest strength reductions exhibit significant activation deficits.