Effects of Normobaric Hypoxia of Varying Severity on Metabolic and Hormonal Responses Following Resistance Exercise in Men and Women

Background/Objectives: Resistance exercise under hypoxic conditions induces various metabolic and hormonal responses, yet the relationship between hypoxia severity and anabolic hormone responses remains unclear. This study aimed to assess the effects of a single bout of resistance exercise on metabolic and hormonal responses in normoxia and three levels of hypoxia in both men and women. Methods: The study involved 16 physically active individuals with at least two years of experience in recreational resistance training. The participants completed resistance exercise sessions in normoxia and normobaric hypoxia at simulated altitudes of 3000 m (H3000), 4000 m (H4000), and 5000 m (H5000). Blood levels of total testosterone (T), cortisol (C), growth hormone (GH), and metabolic variables were measured before and after exercise. Results: In women, severe hypoxia (H4000 and H5000) was found to significantly enhance post-exercise increases in T and GH compared to H3000 (p < 0.05), without affecting C levels. In men, hypoxia (regardless of intensity) did not significantly augment post-exercise changes in T and GH compared to normoxia. In H4000 conditions, an increase in C levels was observed (p < 0.05), leading to an unfavorable reduction in the T/C ratio. Additionally, a reduction in the total number of repetitions performed during the training session and a weakened metabolic response (lactate and creatine kinase) were observed in men at H5000. Conclusions: In women, severe hypoxia (H5000) was found to induce a pronounced hormonal response, particularly in GH levels. The use of severe hypoxia during resistance exercise appears unfavorable in men due to a reduced metabolic response, and diminished exercise capacity, coupled with a failure to induce more favorable changes in the secretion of anabolic hormones than in normoxic conditions.