Changes in corticomotor excitation and inhibition during prolonged submaximal muscle contractions

✍ Scribed by Paul Sacco; Gary W. Thickbroom; Michelle L. Thompson; Frank L. Mastaglia

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 145 KB
• Volume: 20
• Category: Article
• ISSN: 0148-639X
• DOI: 10.1002/(sici)1097-4598(199709)20:9<1158::aid-mus11>3.0.co;2-p

✦ Synopsis

Changes in motor evoked potential (MEP) amplitude, post-MEP silent period duration, and interpolated twitch torque were measured using transcranial magnetic (TMS) and electrical (TES) stimulation during a 20% maximum voluntary contraction of the elbow flexors sustained to exhaustion. TMS-and TES-induced MEP amplitude increased progressively over the contraction period up until the point of exhaustion. The TMSinduced silent period was prolonged only during the second half of the contraction period, the time course being different from that of the MEP responses, whereas the TES-induced silent period did not change. The findings indicate that corticomotor excitability increases during a sustained submaximal voluntary contraction and that, as fatigue develops, there is a progressive buildup of intracortical inhibition. This may represent a mechanism whereby corticomotor output is maintained at an appropriate level to preserve optimal motor unit firing frequencies during a fatiguing contraction.