Common and Divergent Physiological Responses to Hypoxia and Heat.

Exposure to environmental stressors such as hypoxia or heat has emerged as an effective strategy to stimulate physiological adaptations, enhance sport/physical performance and promote health. Both environmental stressors activate shared molecular pathways, notably through the stabilisation of hypoxia-inducible factor-1 alpha and the induction of heat shock proteins, which mediate cellular protection and systemic molecular adaptation. However, hypoxia and heat differ in several aspects, including induction modalities, monitoring methods, metrics used to assess physiological strain and substantial intra- and inter-individual variability. Together, these differences challenge direct comparison and/or combination. Therefore, this current opinion highlights research gaps by critically presenting the common and distinct physiological responses and adaptations to hypoxia and heat exposure. It also emphasises the importance of monitoring internal physiological strain rather than external environmental stress to better account for individual variability. Finally, we propose future research perspectives to address current methodological challenges.