Figure 1.
Overview of the neuromuscular function (NMF) evaluation (panel A) and the experimental protocol (panel B).
NMF evaluation before exercise (PRE) consisted of four parts in the following order: Part I: MVC and electrically evoked quadriceps responses; Part II: determination of the optimal TMS site; Part III: determination of the optimal TMS intensity; Part IV: maximal voluntary activation with TMS. NMF consisted in part I and IV only after the first (MID1), the second (MID2) and the third (POST) bout of cycling.
Figure 2.
Typical traces recorded before (Pre) and after (Post) the 4-h cycling bout of exercise for MVC force and potentiated doublets (panel A), maximal voluntary activation assessed with TMS during contractions at 100%, 75% and 50% MVC (panel B), and motor evoked potential for the rectus femoris muscle recorded during contractions at 100%, 75% and 50% of MVC (panel C).
Arrows indicates the time of transcranial magnetic stimulation (TMS). Dotted lines indicate the end of the cortical silent period (CSP).
Figure 3.
Maximal voluntary contraction (MVC) force (panel A), maximal voluntary activation assessed by interpolated twitch technique (VAFNES, panel B) and maximal voluntary activation assessed by transcranial magnetic stimulation (VATMS, panel C) of the knee extensor muscles, before (PRE), after 80 min (MID1) and 160 min (MID2) of cycling and after the 4-h cycling exercise (POST).
Significantly different from PRE: *P<0.05, **P<0.01, ***P<0.001.
Table 1.
Amplitude of the potentiated high-frequency paired-pulse force (PDb100), potentiated peak twitch force (Pt), estimated resting twitch (ERT) and ratio of paired-pulse peak forces at 10 Hz to 100 Hz (Db10∶100) in the knee extensor muscles, and EMG (M-wave) responses to single-pulse stimuli for rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) muscles before (PRE), after 80 min (MID1) and 160 min (MID2) of cycling and after the 4-h cycling exercise (POST).
Figure 4.
Motor-evoked potential normalized to maximal M-wave amplitude (MEP·Msup−1) at 50, 75 and 100% of maximal voluntary contraction level for rectus femoris (RF, panel A), vastus lateralis (VL, panel B) and vastus medialis (VM, panel C) before (PRE), after 80 min (MID1) and 160 min (MID2) of cycling and after the 4-h cycling exercise (POST).
Significantly different from PRE: *P<0.05.
Table 2.
Corticospinal silent period (ms) of the rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) during contractions at 50, 75 and 100% of maximal voluntary contraction (MVC) of the quadriceps femoris muscles before (PRE), after 80 min (MID1) and 160 min (MID2) of cycling and after (POST) the 4-h cycling exercise.
Table 3.
Total EMG root-mean-square (RMS) normalized by maximal M-wave amplitude (CyclRMS/M) measured at the beginning of each bout and every 20 min during the three 80-min bouts of cycling for the rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) muscles and rating of perceived exertion (RPE), blood glucose, blood lactate and core temperature measured before (PRE) the 4-h cycling exercise and at the end of every 80 min cycling bout.