Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
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©Journal of Sports Science and Medicine (2021) 20, 684 - 689   DOI: https://doi.org/10.52082/jssm.2021.684

Research article
A Combined Hot and Hypoxic Environment during Maximal Cycling Sprints Reduced Muscle Oxygen Saturation: A Pilot Study
Keiichi Yamaguchi, Tomohiro Imai, Haruka Yatsutani, Kazushige Goto 
Author Information
Graduate School of Sport and Health Science, Ritsumeikan University, Shiga, Japan

Kazushige Goto
✉ 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577, Japan
Email: kagoto@fc.ritsumei.ac.jp
Publish Date
Received: 15-02-2021
Accepted: 05-07-2021
Published (online): 01-09-2021
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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%, FiO2 20.9%), normobaric hypoxic (HYP; 23℃, FiO2 14.5%), and hot normobaric hypoxic (HH; 35℃, FiO2 14.5%) environments. Relative humidity was set to 50% in all trials. The vastus lateralis muscle oxygenation was evaluated during exercise using near-infrared spectroscopy. The oxygen uptake (VO2) and arterial oxygen saturation (SpO2) 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 VO2 and SpO2 were significantly lower in the HYP (VO2 = 980 ± 52 mL/min, SpO2 = 82.9 ± 0.8%) and HH (VO2 = 965 ± 42 mL/min, SpO2 = 83.2 ± 1.2%) than in the NOR (VO2 = 1149 ± 40 mL/min, SpO2 = 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.

Key words: Heat stress, normobaric hypoxia, environmental stressor, muscle oxygenation


           Key Points
  • The muscle oxygen saturation was reduced to a greater extent in the combined hot and hypoxia than in hypoxia alone during the second bout of three 15-s maximal cycling sprints, despite similar arterial oxygen saturation.
  • There was no significant difference among conditions for peak and mean power outputs during three 15-s maximal sprints.
  • These results suggest that acute exposure to a combined hot and hypoxia would partially promote local hypoxia in the working muscles without a negative effect on sprint performance.
 
 
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