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. 2017 Sep 20;8:707. doi: 10.3389/fphys.2017.00707

Figure 1.

Figure 1

(A) Picture of the experimental set-up to measure elbow flexors submaximal and maximum voluntary contractions (MVC), voluntary activation (VA), and electromyography (EMG) and placement of EMG electrodes, transcranial magnetic stimulation (TMS), motor point stimulation and Erb's point stimulation. (B) Participants' performed an experimental protocol that consisted of a set of pre-fatigue voluntary contractions (100, 75, 50, 25% MVC, VA-pre), 4 sets of fatiguing contractions and 4 sets of voluntary contractions (100, 75, 50, 25% MVC, VA 1–4) and a set of voluntary contractions (100, 75, 50, 25% MVC) at 5- and 10-min post-fatigue (VA-post 5 and 10). A set of VA contractions was always performed following a set of fatiguing contractions. The VA contraction sets were performed in order to derive an estimated potentiated resting twitch (see Materials and Methods for details) to estimate VA. The black arrows indicate that the participant received several stimuli. The blue boxes indicate VA set contractions and the red bars represent fatiguing set contractions. (C) For each contraction (25–100% MVC) in the VA set, participants received TMS and motor point stimulation (at 2 and 4 s, respectively) and motor point stimulation and Erb's point stimulation (at 2 and 3 s, respectively) following the contraction when the elbow flexors were at rest. The blue trace represents one contraction in the VA set.