Central fatigue in sports and daily exercises. A magnetic stimulation study

Previous transcranial magnetic stimulation (TMS) studies showed exercise-induced depression of motor evoked potentials (MEP). The purpose of the present study was to evaluate changes in MEP size and central motor conduction time (CMCT) after various kinds of exercise of daily life and sports. Changes of both central and peripheral motor conduction were recorded immediately after predominantly aerobic (climbing stairs and jogging) and anaerobic (press-ups, dumb-bell holding, and 400 m-run) exercise. Strength exercise resulted in a significant decrease of MEP amplitudes. Exhausting press-ups reduced the mean MEP amplitude by 33% as compared to pre-exercise value, exhausting dumb-bell holding reduced the mean MEP amplitude by 66%. Aerobic exercises (climbing 600 steps and jogging 50 minutes) did not significantly change MEP amplitudes. The compound motor action potentials (registered after supramaximal peripheral electrical stimulation) remained unchanged after each paradigm. CMCT was not significantly altered by any of the exercises under investigation. Peripheral motor conduction time (PMCT) was slightly lengthened by 4% after isometric dumb-bell holding. PMCT and total motor conduction time were decreased after aerobic exercises, probably due to an increase of temperature of the lower extremities. In conclusion, TMS is a suitable technique for objective evaluation of central fatigue. The present study is the first to show its possible use in sports medicine, indicating that only exhaustive or strength exercises result in reduced MEPs.