Changes in motor cortical excitability during human muscle fatigue.
Open Access
- 15 January 1996
- journal article
- research article
- Published by Wiley in The Journal of Physiology
- Vol. 490 (2), 519-528
- https://doi.org/10.1113/jphysiol.1996.sp021163
Abstract
1. The excitability of the motor cortex was investigated during fatiguing con of the elbow flexors in human subjects. During sustained contractions at 30 and 1 voluntary force (MVC), the short‐latency electromyographic responses (EMG) evoke brachii and brachioradialis by transcranial magnetic stimulation increased in si EMG in the elbow flexors following the evoked muscle potential (silent period), duration during a sustained MVC but not during 30% MVCs nor during a sustained M muscle (adductor pollicis). 2. When the blood supply to brachioradialis was blocked with sphygmomanometer cuff sustained MVC, the changes in EMG responses to transcranial stimulation rapidly control values, This suggests that changes in these responses during fatigue wer small‐diameter muscle afferents. 3. Tendon vibration during sustained MVCs indicated that the changes in the resp cortial stimulation were not mediated by reduced muscle spindle inputs. 4. Muscle action potentials evoked in brachioradialis by electrical stimulation cervicomedullary junction did not increase in size during sustained MVCs. Thus, cortically evoked responses during sustained MVCs reflects a change in cortical Although the silent period following cervicomedullary stimulation lengthened, it substantially shorter than the cortically evoked silent period. 5. The altered EMG responses to transcranial stimulation during fatigue suggest exitation and increased inhibition in the motor cortex. As these changes were un manipulation of afferent input they presumably result from intrinsic cortical pr altered voluntary drive to the motor cortex.Keywords
This publication has 24 references indexed in Scilit:
- Decline in spindle support to alpha‐motoneurones during sustained voluntary contractions.The Journal of Physiology, 1991
- Spinal motor neuron excitability during the silent period after cortical stimulationElectroencephalography and Clinical Neurophysiology/Evoked Potentials Section, 1991
- Percutaneous electrical stimulation of corticospinal pathways at the level of the pyramidal decussation in humansAnnals of Neurology, 1991
- Effects of electric and magnetic transcranial stimulation on long latency reflexesExperimental Brain Research, 1991
- Excitation of the corticospinal tract by electromagnetic and electrical stimulation of the scalp in the macaque monkey.The Journal of Physiology, 1990
- Late muscular responses to transcranial cortical stimulation in manElectroencephalography and Clinical Neurophysiology, 1990
- Electric and magnetic stimulation of human motor cortex: surface EMG and single motor unit responses.The Journal of Physiology, 1989
- Responses in small hand muscles from magnetic stimulation of the human brain.The Journal of Physiology, 1987
- The Effect of Respiratory Muscle Fatigue on Respiratory SensationsClinical Science, 1981
- Voluntary strength and fatigueThe Journal of Physiology, 1954