The interaction between environmental temperature and hypoxia on central and peripheral fatigue during high-intensity dynamic knee extension

This study investigated causative factors behind the expression of different interaction types during exposure to multi-stressor environments. Neuromuscular fatigue rates and time to exhaustion (TTE) were investigated in active males (n=9) exposed to three climates (5°C,50%-rh/23°C,50%-rh/42°C,70%-rh) at two inspired oxygen fractions (0.209/0.125 FIO2; equivalent attitude=4100 m). After 40-mins rest in the environmental conditions, participants performed constant workload (high-intensity) knee extension exercise until exhaustion, with brief assessments of neuromuscular function every 110-s. Independent exposure to cold, heat and hypoxia significantly (p0.198). In contrast, combined exposure to hypoxic-heat reduced TTE by 609-s, showing a significant antagonistic interaction (p=0.003) similarly supported by an increased rate of peripheral fatigue development (increased by 8.3%.min-1). A small decline (