The capacity to perform all-out efforts intermittently with short recovery periods (i.e., < 30 s) is determinant for success in many sports modalities. However, the practice of intermittent sprints has a very high energetic/metabolic cost and neuromuscular demand leading to the instauration of fatigue process. The time-course of sprints performance and neuromuscular recovery after intermittent sprints it is not completely clear. The most frequent tools applied to the investigation of the time-course recovery of sprints performance and neuromuscular fatigue are the surface electromyography (EMG) and neuromuscular electrical stimulation (NMES), beyond the performance itself. However, a methodological problem arises since this methods are capable to identify only the peripheral fatigue (i.e., muscular machinery failure) and central fatigue at spinal level (i.e., spinal cord failure), being undetectable a failure in the descending central motor drive (CMD) generated at corticospinal level. The association of the previous mentioned tools with transcranial magnetic stimulation (TMS) (i.e., technique that is able to stimulate specific pools of motoneurons of the motor cortex) would give additional information about the exact point of the neuromuscular failure during the fatigue process and the time-course of performance and neuromuscular recovery from intermittent sprints. Therefore, we aim to investigate the time-course of sprints performance and neuromuscular fatigue recovery after a set of intermittent sprints with special concerns to the association of EMG, NMES and TMS for track the point of failure during the recovery process. The experimental procedures will occur in 7 sessions. In the first two sessions, the participants will be familiarized with the tests protocols (i.e., sprints in the instrumented ergometer, electrical and transcranial stimulations). In the subsequent session, participants will perform an Incremental Test (IT) to determine the maximal oxygen uptake (VO2max) and peak power output (PPO). After 48 h, will be performed the IST + NMA session (intermittent sprint test - IST; neuromuscular assessment - NMA) with 24 or 48 h of recovery for the subsequent IST + NMA session. The sessions with 24 or 48 h of recovery will be performed in a randomized order and apart by 1 week recovery. The IST + NMA session will be composed by IST (ten 6-s all-out sprints with 30-s of passive recovery) with the NMA being performed before and immediately after IST. The NMA will be composed by two sets of two 5-s maximal isometric voluntary contractions (MVC) with 1 min recovery between the MVCs and 1 min recovery between sets. During the first MVC will be delivery a single TMS and during the second MVC will be delivery the follow sequence: I) single NMES 5 s prior to MVC; II) doublet high frequency NMES during the MVC; III) doublet high frequency NMES 5 s after the MVC; and IV) doublet low frequency NMES 10 s after MVC. The IT and IST will be performed in an instrumented cycle ergometer developed to allow a very short gap between the termination of the IST and the beginning of NMA.
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