Impaired response of human motoneurones to corticospinal stimulation after voluntary exercise
Article first published online: 7 SEP 2004
The Journal of Physiology
Volume 521, Issue 3, pages 749–759, December 1999
How to Cite
Gandevia, S. C., Petersen, N., Butler, J. E. and Taylor, J. L. (1999), Impaired response of human motoneurones to corticospinal stimulation after voluntary exercise. The Journal of Physiology, 521: 749–759. doi: 10.1111/j.1469-7793.1999.00749.x
- Issue published online: 7 SEP 2004
- Article first published online: 7 SEP 2004
- (Received 29 June 1999; accepted after revision 5 October 1999)
- 1Activation of descending corticospinal tracts with transmastoid electrical stimuli has been used to assess changes in the behaviour of motoneurones after voluntary contractions. Stimuli were delivered before and after maximal voluntary isometric contractions (MVCs) of the elbow flexor muscles.
- 2Following a sustained MVC of the elbow flexors lasting 5–120 s there was an immediate reduction of the response to transmastoid stimulation to about half of the control value. The response recovered to control levels after about 2 min. This was evident even when the size of the responses was adjusted to accommodate changes in the maximal muscle action potential (assessed with supramaximal stimuli at the brachial plexus).
- 3To determine whether the post-contraction depression required activity in descending motor paths, motoneurones were activated by supramaximal tetanic stimulation of the musculocutaneous nerve for 10 s. This did not depress the response to transmastoid stimulation.
- 4Following a sustained MVC of 120 s duration, the response to transcranial magnetic stimulation of the motor cortex gradually declined to a minimal level by about 2 min and remained depressed for more than 10 min.
- 5Additional studies were performed to check that the activation of descending tracts by transmastoid stimulation was likely to involve excitation of direct corticospinal paths. When magnetic cortical stimuli and transmastoid stimuli were timed appropriately, the response to magnetic cortical stimulation could be largely occluded.
- 6This study describes a novel depression of effectiveness of corticospinal actions on human motoneurones. This depression may involve the corticomotoneuronal synapse.