Objectives: This overview of systematic reviews aimed to synthesize and critically evaluate the current evidence on the effects of exercise performed under hypoxic or altitude conditions in adults, with particular attention to studies reporting altitude-related clinical outcomes. Materials and Methods: Following PRIOR and PRISMA guidelines, and with the protocol registered in PROSPERO CRD420261325746, a comprehensive search was conducted on 22 February 2026 across Medline/PubMed, Scopus, Web of Science, Epistemonikos, and Preprints.org, using the query “Exercise AND Hypoxic AND Altitude Sickness.” Because the search included “Altitude Sickness,” this review may miss some studies on performance or physiological adaptations under hypoxia. Eligibility was defined according to the PICOS framework, including only systematic reviews with or without meta-analyses in adults exposed to normobaric or hypobaric hypoxia. Methodological quality was assessed using AMSTAR 2. Results: A total of 137 records were identified (114 from databases and 23 through citation tracking), of which 28 systematic reviews met inclusion criteria. Nineteen included quantitative meta-analyses. Structured altitude training strategies—live high–train low (LHTL), live low–train high (LLTH), and live high–train high (LHTH)—were generally associated with improvements in maximal oxygen uptake and hematological parameters, particularly in trained and athletic populations. In contrast, acute hypoxic exposure was consistently associated with reduced exercise performance and increased susceptibility to altitude-related symptoms in unacclimatized individuals. Evidence regarding effects on body composition and metabolic outcomes was heterogeneous and inconsistent. According to AMSTAR 2, most meta-analyses presented critically low or low methodological quality. Conclusions: Exercise under hypoxic conditions may enhances aerobic and hematological adaptations in trained populations, whereas acute exposure tends to impair performance and entails clinical risks. However, given the restricted search strategy, substantial heterogeneity, lack of formal overlap quantification, and the predominance of low methodological quality reviews, these findings should be interpreted with caution. Evidence on metabolic benefits remains limited, highlighting the need for further high-quality systematic reviews and meta-analyses to clarify optimal hypoxic training protocols and outcomes.
Fuentes-Barría et al. (Fri,) studied this question.