Modulation of corticospinal excitability and short intracortical inhibition during submaximal force outputs of the biceps brachii in chronic resistance trained and non-resistance trained individuals

Abstract

Most of studies investigating neural mechanisms during isometric voluntary contractions have focused mainly on the corticospinal tract. Little is known about the modulation of the intracortical inhibitory and facilitatory circuits during different levels of muscle activation. Also, studies using a transcranial magnetic stimulation (TMS) to examine neural adaptations have shown that excitability of the corticospinal tract is modulated following chronic resistance training. But, the effects of a long period of resistance training on the modulation of intracortical interactions has not examined yet. The current study was designed to assess corticospinal excitability and short intracortical inhibition (SICI) modulation using two different TMS protocols during different target forces. Using these techniques, we sought to determine whether a central nervous system excitability and SICI system changes as a function of contraction intensity, as well as determine whether these probable changes were similar in chronic resistance trained (RT) and non-RT subjects.