Almudehki, F. A., Girard, O., Grantham, J., Berger, N., & Racinais, S. (2009). Neuro-muscular fatigue development during repeated cycling sprints in a hot environment. ACSM 56th Annual Meeting, Seattle, Washington, Presentation Number 2676.

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This study investigated the contributions of central and peripheral factors in the development of neuromuscular fatigue during repeated sprints in a hot environment. Males (N = 10) performed two 38-minute blocks of repeated sprint trials consisting of eight 6-second sprints of maximal cycling interspaced by five minutes of active recovery. Trials were performed in control (24C; 24% RH) and hot (40C; 40% RH) environmental conditions in random order After each sprint, maximal percutaneous electrical stimulations were applied to the femoral nerve both at rest and during maximal voluntary contraction. To examine potential impairment in central drive, changes in EMG activity of the vastus lateralis muscle (normalized to the M-wave amplitude as well as muscle activation) were quantified during maximal voluntary contraction of the knee extensors. Peripheral fatigue was assessed by examining the amplitude of the M-wave and twitch contractile properties following single stimuli. Both core and skin temperatures were monitored throughout by a telemetric pill and patches respectively.

Rating of perceived exertion, heart rate, and skin temperature were significantly higher in the hot condition when compared to the control condition. Core temperature, peak power production, maximal voluntary contraction, and muscle electrical activity during the maximal voluntary contractions or the cycling sprints were not influenced by the hot humid environmental condition in this pattern of exercise.

Implication. Power is not affected by hot conditions while other physiological factors are. [This is an example that if one inferred from changed physiological factors that performance would also change, they would be wrong.]

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