Acute performance and physiological responses to repeated‐sprint exercise in a combined hot and hypoxic environment. Issue 12 (26th June 2020)

• Record Type: Journal Article
• Authors: Yamaguchi, Keiichi; Kasai, Nobukazu; Hayashi, Nanako; Yatsutani, Haruka; Girard, Olivier; Goto, Kazushige
• Is Part Of: Physiological reports. Volume 8:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-06-26
• Subjects: combination of stressors -- heat stress -- hypoxia -- repeated‐sprints; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.14466
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: We investigated performance, energy metabolism, acid–base balance, and endocrine responses to repeated‐sprint exercise in hot and/or hypoxic environment. In a single‐blind, cross‐over study, 10 male highly trained athletes completed a repeated cycle sprint exercise (3 sets of 3 × 10‐s maximal sprints with 40‐s passive recovery) under four conditions (control [CON; 20℃, 50% rH, FiO2 : 20.9%; sea level], hypoxia [HYP; 20℃, 50% rH, FiO2 : 14.5%; a simulated altitude of 3, 000 m], hot [HOT; 35℃, 50% rH, FiO2 : 20.9%; sea level], and hot + hypoxia [HH; 35℃, 50% rH, FiO2 : 14.5%; a simulated altitude of 3, 000 m]). Changes in power output, muscle and skin temperatures, and respiratory oxygen uptake were measured. Peak (CON: 912 ± 26 W, 95% confidence interval [CI]: 862–962 W, HYP: 915 ± 28 W [CI: 860–970 W], HOT: 937 ± 26 W [CI: 887–987 W], HH: 937 ± 26 W [CI: 886–987 W]) and mean (CON: 808 ± 22 W [CI: 765–851 W], HYP: 810 ± 23 W [CI: 765–855 W], HOT: 825 ± 22 W [CI: 781–868 W], HH: 824 ± 25 W [CI: 776–873 W]) power outputs were significantly greater when exercising in heat conditions (HOT and HH) during the first sprint ( p < .05). Heat exposure (HOT and HH) elevated muscle and skin temperatures compared to other conditions ( p < .05). Oxygen uptake and arterial oxygen saturation were significantly lower in hypoxic conditions (HYP and HH) versus the other conditions ( p < .05). In summary, additional heat stress when sprinting repeatedly in hypoxia improved performance (early during exercise), while maintaining low arterial oxygen saturation. Abstract : The present study investigated performance, energy metabolism, acid‐base balance, and endocrine responses to repeated sprint exercise in a hot and/or hypoxic environment. Our findings suggest that additional heat stress to hypoxia enhances repeated sprint performance with maintaining low arterial oxygen saturation.