Author(s): BOULARES, A., DUPUY, O., LUIGI BRAGAZZI, N., PICHON, A., Institution: POITIERS UNIVERSITY , Country: FRANCE, Abstract-ID: 1276

INTRODUCTION:
Intermittent hypoxia (IH) is widely used to enhance athletic performance, yet evidence remains fragmented across diverse protocols (LLTH, LHTL, LHTLH) and training modalities. Recent systematic reviews (SRs), meta-analyses (MAs), and network meta-analyses (NMAs) report heterogeneous findings, limiting practical recommendations. This umbrella review aimed to synthesize and critically appraise the highest level of evidence regarding the effects of IH protocols on physical performance outcomes.
METHODS:
Following PRIOR guidelines (PROSPERO CRD42024465481), seven databases were searched from inception to June 2025. Eligible studies were SRs with or without MA/NMA investigating systemic IH strategies (LLTH, LHTL, LHTLH) and reporting at least one performance outcome. Methodological quality was assessed using AMSTAR-2. Overlap between reviews was quantified using the Corrected Covered Area (CCA).
RESULTS:
Twenty-two SRs were included, encompassing 487 unique primary studies and 5,333 participants (13–67 years). Fourteen included MAs and three included NMAs. Overall overlap was low (CCA=3.5%). IH protocols demonstrated significant improvements in aerobic and anaerobic performance. LHTL combined with low-altitude training showed large effects on V̇O₂max (SMD=1.04, 95%CI [0.47–1.61]). Simulated altitude training produced similar effects (SMD=0.91 [0.44–1.38]). Repeated sprint training in hypoxia (RSH) improved V̇O₂max (SMD=0.76 [0.29–1.23]) and repeated-sprint ability (SMD=0.46, p=0.05). Hypoxic HIIT elicited greater V̇O₂max gains than normoxia (SMD=1.14; SMD=0.68 in recent MA). RSH with voluntary hypoventilation improved sprint fatigue resistance (SMD=0.60, p=0.005). Hematological adaptations were inconsistent and primarily observed with prolonged exposure (>12 h·day⁻¹). Methodological quality was predominantly low to critically low.
CONCLUSION:
IH training enhances multiple domains of performance, with the strongest evidence supporting LHTL, hypoxic HIIT, and RSH for aerobic and repeated-sprint outcomes. Benefits appear largely mediated by peripheral and metabolic adaptations rather than robust erythropoiesis in most protocols. However, methodological limitations and protocol heterogeneity temper certainty. Optimizing hypoxic dose and individualizing prescriptions are critical to maximize performance benefits.