A Combined Hot and Hypoxic Environment during Maximal Cycling Sprints Reduced Muscle Oxygen Saturation: A Pilot Study.
Journal:
Journal of sports science & medicine
PMID:
35321130
Abstract
The present study investigated the effects of a combined hot and hypoxic environment on muscle oxygenation during repeated 15-s maximal cycling sprints. In a single-blind, cross-over study, nine trained sprinters performed three 15-s maximal cycling sprints interspersed with 7-min passive recovery in normoxic (NOR; 23℃, 50%, FiO 20.9%), normobaric hypoxic (HYP; 23℃, FiO 14.5%), and hot normobaric hypoxic (HH; 35℃, FiO 14.5%) environments. Relative humidity was set to 50% in all trials. The muscle oxygenation was evaluated during exercise using near-infrared spectroscopy. The oxygen uptake (VO) and arterial oxygen saturation (SpO) were also monitored. There was no significant difference in peak or mean power output among the three conditions. The reduction in tissue saturation index was significantly greater in the HH (-17.0 ± 2.7%) than in the HYP (-10.4 ± 2.8%) condition during the second sprint (p < 0.05). The average VO and SpO were significantly lower in the HYP (VO = 980 ± 52 mL/min, SpO = 82.9 ± 0.8%) and HH (VO = 965 ± 42 mL/min, SpO = 83.2 ± 1.2%) than in the NOR (VO = 1149 ± 40 mL/min, SpO = 90.6 ± 1.4%; p < 0.05) condition. In conclusion, muscle oxygen saturation was reduced to a greater extent in the HH than in the HYP condition during the second bout of three 15-s maximal cycling sprints, despite the equivalent hypoxic stress between HH and HYP.