Impact of Sprint Duration With Fixed Recovery on Acute Physiological and Performance Responses to Repeated Cycle Sprints in Hypoxia in Male and Female Sprinters.

Repeated short sprints (≤ 10 s) in hypoxia are often used to enhance performance, but acute responses to longer sprints (> 10 s) performed in a repeated-sprint format with short recovery periods (∼30 s) remain unclear. We examined performance and physiological strain during repeated short (10-s) and long (15-s) sprints with identical recovery (30 s) comparing acute responses between sexes. Sixteen highly trained sprinters (7 females) performed 7 × 10-s (10:30) and 15-s (15:30) sprints with 30-s rest in normobaric hypoxia (FiO2: 0.15), using a randomized cross-over design. Average mean power output across the seven sprints was lower in 15:30 than 10:30 (6.30 ± 0.44 vs. 6.85 ± 0.82 W/kg; p < 0.001). Sprint decrement score (Sdec) was larger in 15:30 than 10:30 (-17.9 ± 4.8% vs. -13.1 ± 4.6%; p < 0.001). Average pulse oximetry-derived peripheral oxygen saturation (SpO2) across the seven sprints was lower in 15:30 than 10:30 (87.1 ± 4.2% vs. 89.7 ± 2.7%; p < 0.001), whereas the magnitude of change from sprint 1 to sprint 7 did not clearly differ between conditions. Heart rate increased across sprints (Δsprint1-7: +9.2 ± 5.3% and p < 0.001), independently of condition (p = 0.652). ΔSpO2 correlated with ΔSdec (r = 0.609 and p = 0.012). Female athletes experienced smaller performance declines than males in both conditions (p = 0.001). Longer repeated sprints with identical rest in hypoxia impair mechanical output while inducing greater physiological strain, with comparatively smaller performance reductions in females.