Fatigue after short (100-m), medium (200-m) and long (400-m) treadmill sprints

Abstract

The aim of this study was to compare the aetiology of neuromuscular fatigue following maximal sprints of different distances. It was hypothesized that increasing the distance would modify the type of peripheral and induce central fatigue. 11 subjects performed 100-, 200- and 400-m sprints on a motorized instrumented treadmill. Neuromuscular function, evaluated before (Pre), 30 s after (Post), and 5 and 30 min after the sprints (Post5 and Post30), consisted in determining maximal voluntary knee extensors torque (MVC), maximal voluntary activation of the knee extensors (%AL), maximal compound muscle action potential amplitude and duration on vastus lateralis, single twitch (Tw), and low- (Db10) and high-frequency torque. Compared with peak values, running speed decreased by 8%, (P < 0.01), 20% (P < 0.001) and 39% (P < 0.001) at the end of the 100-, 200- and 400-m sprints, respectively. MVC was not altered following 100 and 200 m, but decreased by 14% (P < 0.001) after the 400 m, was still depreciated Post5 (-11%, P < 0.01) and went back to initial values Post30. A decrease in %AL (-6.0%, P < 0.01) was observed Post5 for the 400 m. Tw, Db10 and low-to-high doublets ratio decreased Post-sprints and were not recovered Post30 after all sprints. Single maximal sprints of 100-400 m did not alter sarcolemmal excitability but induced progressive and substantial low-frequency fatigue and a slight reduction in neural drive with increasing sprint duration. Despite altered single or paired stimulations, MVC strength loss was detected only after the 400 m.

Maturation-related differences in neuromuscular fatigue after a short-term maximal run

“…The speed deceleration and the post-exercise blood lactate and blood pH levels indicate that the subjects made an allout effort. In line with previous studies [6,7], adults showed a decrease in MVc torque (-16.1%) after the run. children and adolescents presented no change in MVc despite the loss of running speed, which might be due to faster recovery before the post-fatigue tests.…”

“…Thus, in line with the recent study by Tomazin et al [7], the peripheral fatigue could have been caused by the processes beyond the sarcolemma. consistently with earlier studies [4,6], both adolescents and adults showed a decrease in MRTD that is limited by the rate of crossbridge transition from the weakly to strongly bound state [25].…”

“…Both the present and the previous studies [4,7] suggest that the M-wave remains unchanged after a shortterm maximal run. Although depressed M-waves have been observed after very short repeated sprint (12 × 40 m) [6] and maximal jumping exercise [22], it may be that the neuromuscular junction and the sarcolemma retain their functionality during continuous anaerobic long-sprint distances.…”

“…Previous studies addressing neuromuscular fatigue in adults have consistently shown significant reductions (from -35 to -8%) in the plantar flexor / knee extensor PT after short-term high-intensity running efforts [4][5][6][7]. Accordingly, both adolescents and adults presented peripheral fatigue in this study.…”

“…Fatigue can be caused by impairments in central and peripheral processes [3]. In the context of high-intensity running or jumping exercise, fatigue has mainly been attributed to the peripheral processes, including the excitation-contraction (E-c) coupling and cross-bridge cycling [4][5][6][7], while central factors seem to play a minor a role [6,7]. Unfortunately, studies of this type have so far focused mainly on grown-up subjects.…”