Minimal Effects of Moderate Normobaric Hypoxia on the Upper Body Work–Time Relationship in Recreationally Active Women

Minimal Effects of Moderate Normobaric Hypoxia on the Upper Body Work–Time Relationship in Recreationally Active Women: High Altitude Medicine &Biology, Ahead of Print.



Abstract

Background: Sex-based differences in metabolism and morphological characteristics may result in unique exercise responses during periods of limited oxygen availability.



Purpose: To evaluate the effects of moderate normobaric hypoxia on the parameters of the work–time relationship during upper body exercise in women.



Materials and Methods: Thirteen recreationally active women (age: 22.7 ± 2.6 years; height: 167 ± 8.6 cm; weight: 66.4 ± 9.7 kg; body fat: 27.6% ± 5% body fat) completed a maximal graded exercise test in both normobaric hypoxia (H; fraction of inspired oxygen (FiO2) = 0.14) and normoxia (N; FiO2 = 0.20) on an arm ergometer to determine peak oxygen uptake (VO2peak) and peak power output (PPO). Each participant completed four constant, work rate, arm-cranking time-to-exhaustion tests at 90%–120% PPO in both environmental conditions. Linear regression was used to estimate critical power (CP) and anaerobic capacity (W′) through the work–time relationship during the constant work rate tests. Paired sample t-tests compared mean differences between VO2peak, PPO, CP, and W′ between conditions (normoxia vs. hypoxia). Two-way (condition × intensity) repeated measures analysis of variance (ANOVA) was used to compare total work (TW) and time to exhaustion.



Results: Hypoxia significantly reduced VO2peak (N: 1.73 ± 0.31 L·minute−1 vs. H: 1.62 ± 0.27 L·minute−1, p = 0.008), but had no effects on PPO (N: 78.08 ± 14.51 W vs. H: 75.38 ± 13.46 W, p = 0.09), CP (N: 57.44 ± 18.89 W vs. H: 56.01 ± 12.36 W, p = 0.55), and W′ (N: 4.81 ± 1.01 kJ vs. H: 4.56 ± 0.91 kJ, p = 0.51). No significant condition × intensity interactions were noted for TW or time to exhaustion (p > 0.05).



Conclusions: Moderate normobaric hypoxia significantly reduced VO2peak, but had minimal effects on CP and W′ using the work–time model in women.