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Post-exercise depression of motor evoked potentials as a function of exercise duration
A Samii1, E M Wassermann, M Hallett
1Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1428, USA.
Electroencephalography and Clinical Neurophysiology
|November 18, 1997
Summary
Post-exercise depression in motor evoked potentials (MEPs) is linked to prolonged, fatiguing muscle activation. This study found that MEP depression only occurs after extended exercise, not before reaching muscle fatigue.
Area of Science:
- Neuroscience
- Exercise Physiology
Background:
- Motor evoked potentials (MEPs) exhibit post-exercise facilitation (brief activation) and post-exercise depression (prolonged activation).
- The precise onset of post-exercise depression relative to muscle fatigue is not well-defined.
Purpose of the Study:
- To investigate if post-exercise depression occurs before the onset of muscle fatigue.
- To determine the exercise duration required to elicit post-exercise depression.
Main Methods:
- 12 healthy subjects performed isometric wrist extension at 50% maximal voluntary contraction.
- Exercise duration was increased until volitional fatigue (inability to maintain force).
- MEPs were recorded from the extensor carpi radialis muscle throughout and after exercise.
Main Results:
- Mean exercise duration to fatigue was 130 seconds.
- Post-exercise depression was observed only after exercise durations exceeding 90 seconds.
- Depression did not occur before the point of fatigue was reached.
Conclusions:
- Post-exercise depression is a phenomenon associated with prolonged, fatiguing muscle contractions.
- Detecting post-exercise depression requires sustained muscle activation beyond a significant duration.