Effects of High-Intensity Interval Training with Blood Flow Restriction Versus Normobaric Hypoxia on Physiological...

High-intensity interval training (HIIT) is an efficient exercise strategy capable of eliciting acute cardiovascular and metabolic responses. Blood flow restriction (BFR) and normobaric hypoxia (NH) have been proposed as exposures to intensify physiological stress during exercise; however, comparative evidence between both strategies remains limited. The aim of this study was to compare acute physiological responses in HIIT protocols performed under BFR and NH in apparently healthy young men. Eight volunteers completed two HIIT sessions in this fixed-order within-subject repeated-measures study: one with BFR and one with NH (simulated altitude: 3536 m above sea level; FiO₂ ≈ 13.5%). Blood glucose, peripheral oxygen saturation (SpO₂), heart rate, and blood pressure were repeatedly measured during the exercise protocol. After Bayesian analysis, no evidence of differences in glycemic response was observed, while heart rate and diastolic blood pressure responses appeared broadly comparable between conditions. However, SpO₂ was consistently lower during NH, whereas systolic blood pressure values were higher under BFR. Although both BFR and NH induced acute physiological responses characteristic of HIIT, distinct physiological profiles were observed. NH was associated with greater systemic hypoxemic stress, whereas BFR showed higher systolic pressor responses.