Discussion
voluntary muscle contractions, fatigue
CONTRACTION, CONTRACTIONS
The present study assessed the effects of a potent antimuscarinic drug on MEP area and TMS-evoked SP during voluntary contractions. To achieve this, a contraction protocol was used to assess cholinergic effects during brief contractions of 10%, 25%, 50%, 75%, and 100% MVC. This was followed by a second protocol that assessed MEPs during the same contraction intensities, however, a consistent within-subject and between-subject level of fatigue was induced before each contraction. The main finding was that the antimuscarinic drug reduced the TMS-evoked SP during unfatigued contractions but did not affect MEPs under any contraction condition. This suggests that the cholinergic system does not influence corticospinal excitability during voluntary muscle contractions, but instead affects inhibitory circuits associated with the TMS-evoked silent period.