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The human force:velocity relationship; activity in the knee flexor and extensor muscles before and after eccentric
O M Rutherford1, C Purcell, D J Newham
1Applied Biomedical Research Group, Division of Physiology, School of Biomedical Sciences, King's College London, Guy's Campus, London, UK.
European Journal of Applied Physiology
|June 8, 2001
Summary
Eccentric contraction training did not improve maximal voluntary forces or alter muscle activation strategies in humans. Neural learning or activation patterns do not explain the lower-than-expected eccentric forces observed.
Area of Science:
- Biomechanics
- Human Physiology
- Motor Control
Background:
- The human force-velocity relationship often shows lower eccentric forces than predicted.
- Unique activation strategies and neural learning are potential explanations for this phenomenon.
Purpose of the Study:
- To investigate the impact of eccentric contraction practice on the force-velocity relationship of knee extensors.
- To assess changes in agonist and antagonist muscle activity following eccentric training.
Main Methods:
- Eight healthy adults underwent a 4-week eccentric contraction training program.
- Maximal voluntary contractions (MVCs) were performed isokinetically at various speeds before and after training.
- Electromyogram (EMG) activity of agonist and antagonist muscles was recorded.
Main Results:
- Eccentric training did not significantly alter force production or relative EMG activity.
- A trend towards increased dynamic forces was observed post-training.
- Eccentric MVC forces became similar to isometric forces after training, unlike before.
Conclusions:
- Neural learning mechanisms do not appear to explain the reduced voluntary eccentric forces in humans.
- Total muscle activation strategies are also unlikely to be the underlying cause.