Effects of High-Intensity Interval Training in Normobaric Hypoxia on Anaerobic Performance in Young Untrained Men Across Different Hypoxic Exposure Models

Background: Normobaric hypoxia is increasingly used as an additional environmental stimulus in training programs; however, its practical role in improving anaerobic performance remains unclear. This study analyzed how a four-week high-intensity interval training (HIIT) program performed under different hypoxic exposure models affected selected anaerobic performance indices in young men. Methods: Forty-five healthy, non-elite physically active men completed the study. Participants were assigned to one of four groups: control, normoxic training, live low–train high group, and live high–train low group. The training intervention consisted of 12 HIIT sessions performed over four weeks. Anaerobic performance was assessed before and after the intervention using a 20-s maximal cycling sprint test. Results: No significant group × time interactions were found for any variables obtained from the 20-s maximal cycling sprint test, including peak power (PP; p = 0.109, ηp2 = 0.136), relative peak power (rel_PP; p = 0.641, ηp2 = 0.040), relative mean power (rel_MP; p = 0.438, ηp2 = 0.063), relative total work (rel_TW; p = 0.515, ηp2 = 0.054), fatigue index (FI; p = 0.231, ηp2 = 0.099), and time to peak power (tPP; p = 0.673, ηp2 = 0.036). Conclusions: The findings suggest that, under the applied conditions, normobaric hypoxia does not provide a sufficient additional stimulus to enhance anaerobic performance adaptations. From an applied exercise physiology perspective, the specificity and structure of the training stimulus are critical when designing short-term HIIT interventions. They may be more important than hypoxic exposure itself for improving short-duration maximal cycling sprint performance.