Voluntary activation of knee extensor muscles with transcranial magnetic stimulation

We discovered that the contemporary procedure for assessing voluntary activation of knee extensor muscles with transcranial magnetic stimulation (TMS) is invalid. TMS activates too few agonist quadriceps motoneurons and many antagonist hamstrings to estimate resting twitch accurately. A modified procedure, in which TMS-evoked superimposed twitches are considered together from femoral nerve stimulation, valid but only select individuals who meet rigorous eligibility criteria.