The effects of normobaric hypoxic resistance training on muscle strength in healthy adults.

Normobaric hypoxic resistance training (NHRT) has emerged as a novel approach to enhancing muscle strength, potentially offering advantages over conventional resistance training. However, its efficacy in healthy adults remains uncertain. This systematic review and meta-analysis aimed to evaluate the effects of NHRT on muscle strength indicators, including one-repetition maximum (1RM), isometric strength, and isokinetic strength, in healthy adults.

Methods: Following PRISMA 2020 guidelines, four databases (PubMed, Web of Science, SportDiscus, and CNKI) were searched from inception to October 25, 2024, for randomized controlled trials. Study quality was assessed using the Cochrane Risk of Bias tool. Effect sizes were calculated using Review Manager 5.4.

Results: A total of 22 RCTs involving 487 healthy adults were included. The meta-analysis revealed a significant small-to-moderate improvement in 1RM (SMD = 0.22, 95% CI [0.06, 0.38]) but no statistically significant effects on isometric strength (SMD = 0.32, 95% CI [-0.05, 0.70]) and isokinetic strength (SMD = 0.25, 95% CI [-0.11, 0.62]). Subgroup analyses indicated that oxygen concentrations of 14-16% and training loads of 60-80% 1RM produced the most substantial gains, particularly among untrained participants.

Conclusions: NHRT is a promising strategy for enhancing 1RM in healthy adults, with its effectiveness influenced by hypoxic levels, training load, and baseline training status. Optimal outcomes were observed at oxygen concentrations of 14-16% and moderate training loads (60-80% 1RM), particularly in untrained individuals. Further high-quality studies are warranted to confirm these outcomes and explore the underlying mechanisms.Registration number on PROSPEROCRD42024547100.