Acute Effects of Moderate Altitude and Normoxia on Physiological, Neuromuscular, and Performance Responses in Highly Trained Swimmers

Background: Acute exposure to moderate altitude may modify physiological responses to exercise, yet its effects on neuromuscular function and repeated-sprint performance in highly trained swimmers remain unclear. This study compared the acute effects of moderate altitude and normoxia during the same training protocol. Methods: A quasi-experimental repeated-measures design was employed, with six highly trained swimmers completing testing sessions under both normoxic and moderate-altitude conditions, separated by 1 week. Peripheral oxygen saturation (SpO2), heart rate (HR), countermovement jump (CMJ), squat jump (SJ), rating of perceived exertion (RPE), blood lactate concentration ([La−]), and repeated-sprint swimming performance (4 × 50 m) were assessed. Results: SpO2 was lower at altitude than in normoxia (p < 0.001, ηp2 = 0.915), while HR showed a condition × time interaction (p = 0.007, ηp2 = 0.391). CMJ, SJ, RPE, and [La−] did not differ between conditions. Sprint performance declined across repetitions for 15 m and 25 m splits (p ≤ 0.002), but no altitude effect or altitude × repetition interaction was observed for any performance measure (p > 0.18). Conclusion: Acute moderate-altitude exposure induced physiological changes, particularly reduced SpO2, without impairing neuromuscular function, perceived exertion, lactate responses, or repeated-sprint swimming performance.