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Changes in corticomotor excitability after fatiguing muscle contractions
P Sacco1, G W Thickbroom, M L Byrnes
1Centre for Neuromuscular and Neurological Disorders, Australian Neuromuscular Research Institute, University of Western Australia, Queen Elizabeth II Medical Centre, Perth, Western Australia 6009, Australia. psacco@cyllene.uwa.edu.au
Muscle & Nerve
|December 5, 2000
Summary
Fatigue reduces brain and spinal cord excitability. A weak muscle contraction can abolish this post-exercise depression, suggesting spinal mechanisms contribute to reduced corticomotor excitability.
Area of Science:
- Neuroscience
- Exercise Physiology
- Motor Control
Background:
- Fatiguing exercise impacts neural pathways controlling muscle activity.
- Understanding how different exercise types affect corticomotor excitability is crucial for rehabilitation and performance.
Purpose of the Study:
- To determine if exercise type and duration influence corticomotor excitability after fatigue.
- To investigate the role of spinal versus central mechanisms in post-exercise excitability changes.
Main Methods:
- Comparing motor evoked potential (MEP) responses of the biceps brachii using transcranial magnetic stimulation (TMS).
- Subjects performed either a 60-second maximal voluntary contraction (MVC) or a sustained 20% MVC to exhaustion.
- MEP responses were recorded at rest and during a weak tonic contraction.
Main Results:
- Resting MEP amplitude significantly decreased after both maximal and submaximal fatiguing protocols.
- Facilitated MEP amplitude showed a smaller, transient decrease only after the sustained submaximal exercise.
- A weak tonic contraction abolished the post-exercise depression in resting MEP amplitude.
Conclusions:
- Both maximal and submaximal fatiguing exercise reduce corticomotor excitability.
- Spinal mechanisms contribute to the observed decrease in excitability following fatiguing exercise.
- The type and duration of exercise differentially affect the recovery of corticomotor excitability.