The Acute Effects of Normobaric Hypoxia on Strength, Muscular Endurance and Cognitive Function: Influence of Dose and Sex

Abstract

The aim of this study was to examine the acute effects of different levels of hypoxia on maximal strength, muscular endurance, and cognitive function in males and females. In total, 13 males (mean ± SD: age, 23.6 ± 2.8 years; height, 176.6 ± 3.9 cm; body mass, 76.6 ± 2.1 kg) and 13 females (mean ± SD: age, 22.8 ± 1.4 years; height, 166.4 ± 1.9 cm; body mass, 61.6 ± 3.4 kg) volunteered for a randomized, double-blind, crossover study. Participants completed a one repetition strength and muscular endurance test (60% of one repetition maximum to failure) for squat and bench press following four conditions; (i) normoxia (900 m altitude; FiO2: 21%); (ii) low dose hypoxia (2000 m altitude; FiO2: 16%); (iii) moderate dose hypoxia (3000 m altitude; FiO2: 14%); and (iv) high dose hypoxia (4000 m altitude; FiO2: 12%). Heart rate, blood lactate, rating of perceived exertion, and cognitive function was also determined during each condition. The one repetition maximum squat (p = 0.33) and bench press (p = 0.68) did not differ between conditions or sexes. Furthermore, squat endurance did not differ between conditions (p = 0.34). There was a significant decrease in bench press endurance following moderate (p = 0.02; p = 0.04) and high (p = 0.01; p = 0.01) doses of hypoxia in both males and females compared to normoxia and low dose hypoxia, respectively. Cognitive function, ratings of perceived exertion, and lactate were also significantly different in high and moderate dose hypoxia conditions compared to normoxia (p < 0.05). Heart rate was not different between the conditions (p = 0.30). In conclusion, high and moderate doses of acute normobaric hypoxia decrease upper body muscular endurance and cognitive performance regardless of sex; however, lower body muscular endurance and maximal strength are not altered.

Sex comparisons in physiological and cognitive performance during hypoxic challenge

“…Though accounting for a small percentage of SpO 2 , these results are consistent with Archiza et al (2020) findings regarding sex differences in diaphragmatic muscle fatigue under acute hypoxia. However, our finding of lower SpO 2 for females is inconsistent with prior work using less severe altitudes that found no sex differences ( Hohenauer et al, 2022 ; Karayigit et al, 2022 ). The altitudes examined here most closely align with the 8% O 2 used by Archiza et al (2020) .…”

“…The altitudes examined here most closely align with the 8% O 2 used by Archiza et al (2020) . Moreover, given the small sample sizes used in previous work ( Hohenauer et al, 2022 ; Karayigit et al, 2022 ), their null result for sex differences in SpO 2 was possibly due to inadequate power. The larger sample size used in our study afforded us a better opportunity to assess these differences, and our results did indicate that the effect was quite small with sex, age, and BMI only accounting for 6% variance in SpO 2 ( Table 3 ).…”

“…Also looking at respiratory effects of hypoxia, Camacho-Cardenosa et al (2022) found that males had an increase in minute ventilation and a steeper initial decrease in peripheral oxygen saturation (SpO 2 ) compared to females during a 7 h moderate hypoxia exposure (15% O 2 ). Two additional studies examined sex differences in the effects hypoxia have on cold stress ( Hohenauer et al, 2022 ) and muscle endurance ( Karayigit et al, 2022 ), but both studies found no difference in SpO2 between sexes during those moderate hypoxia exposures. These inconsistent findings suggest that there may be sex differences in physiological response to hypoxic challenge.…”

Recommendations for Women in Mountain Sports and Hypoxia Training/Conditioning

“…Finally, resistance training in hypoxia can lead to structural and functional skeletal muscle adaptations, but potential sex-based differences have not been investigated [ 182 ]. While no difference was found between women and men performing squat and bench press at both maximal (i.e.…”

Biological Mechanisms Underlying Physical Fitness and Sports Performance: An Editorial

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