Delayed facilitation of motor cortical excitability following repetitive finger movements

Objectives. To define motor cortical excitability changes occurring at vari ous times after non-fatiguing bimanual exercise of the index fingers. Methods: Twenty healthy right-handed subjects were studied with transcrania l magnetic stimulation (TMS) of the right non-dominant hemisphere. They Per formed regular (3-4/s) repetitive opening-closing bilateral movements of th e index finger onto the thumb. Motor evoked potentials (MEPs) of the left f irst dorsal interosseus (FDI) and rate of the repetitive finger movements w ere determined (1) before exercise, (2) immediately following 3 exercise pe riods of 30, 60 and 90 s, and (3) over a subsequent 30 min rest period. Results: Rate of movement did not show significant change during any of the exercise periods but did increase significantly when tested after 15 min o f rest. MEPs immediately after 30 and 60 a of exercise were facilitated whe reas MEPs after 90 s of exercise did not differ from baseline measures. MEP amplitudes were significantly increased after rest of approximately 15 min compared to the baseline MEPs. In contrast, motor potentials evoked by per ipheral nerve stimulation were unchanged throughout the experimental test p eriods. Conclusions: Motor cortical excitability relating to an intrinsic finger mu scle (FDI) was facilitated beginning 15 min after a brief period of non-for ceful, repetitive activity of that muscle. This delayed facilitation of mot or cortex after exercise may represent a form of short-term potentiation of motor cortical excitability. (C) 2000 Elsevier Science Ireland Ltd. All ri ghts reserved.