title: Neuromuscular failure is unlikely to explain the early exercise cessation in hot ambient conditions.
abstract: Baseline, postexercise (20 min cycling) and postexhaustion (incremental test) neuromuscular function was assessed in control (24°C) and hot (40°C) conditions. Heat affects the plantar flexors and knee extensors differently, but most of the effects of heat (e.g., M-wave decrement) and fatigue (e.g., voluntary activation and H-reflex decrement) were independent of each other. However, peripheral fatigue of the knee extensors was lower at exhaustion in hot than neutral environment (peak twitch decrement from baseline to exhaustion: -19% vs. -33%, p < .05). In addition, heat had no negative effect on transcranial magnetic stimulation responses during cycling, and neuromuscular failure is unlikely to explain the early exercise cessation in the heat (13 min 50 s vs. 17 min 9 s) that occurred when participants reached maximal perceived exertion (19.2 vs. 19.1, ns) with higher core temperature (38.7°C vs. 38.2°C, p < .05) and heart rate (184 bpm vs. 179 bpm, p < .05).
authors.affiliation: Research and Education Centre, ASPETAR-Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. sebastien.racinais@aspetar.com
authors.forename: Sébastien
authors.initials: S
authors.lastname: Racinais
authors.forename: Olivier
authors.initials: O
authors.lastname: Girard
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D009468:Neuromuscular Diseases / Q000503:physiopathology*; D013696:Temperature; D050781:Transcranial Magnetic Stimulation