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


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.



Document Type





altitude, critical power, fatigue, upper-body exercise

Publication Date


Journal Title

High Altitude Medicine and Biology