Oxygen Saturation, Heart Rate, and Blood Lactate Responses to Acute Simulated Altitude in Sprinters and Middle- and Long-Distance Athletes

BackgroundAcute hypoxia reduces oxygen availability and may increase physiological strain during supramaximal exercise.This study examined peripheral oxygen saturation (SpO₂), heart rate (HR), and blood lactate responses to graded simulated altitude in Indian sub-elite sprinters and middle-and long-distance (MD/LD) athletes. MethodsForty-four male athletes, comprising 22 sprinters and 22 MD/LD athletes, completed a 30-second Wingate test under normoxia and simulated altitudes of 2000 and 3000 m.Hypoxic trials followed 60 minutes of exposure, and trials were separated by at least 72 hours.SpO₂ was measured at rest and immediately postexercise.HR was assessed at rest, during Wingate exercise, and at three-minute recovery.Blood lactate was measured at rest, immediately post-exercise, and at six recovery points up to 30 minutes.Mixed-design repeated-measures analysis of variance (ANOVA) examined group, altitude, and time or phase effects. ResultsSpO₂ decreased progressively with altitude and fell further after exercise.Altitude, time, and altitude × time effects were significant (all p < 0.001), with an altitude effect size of ηp² = 0.991.No group-related SpO₂ effects were significant.HR increased with altitude and remained above resting values at three-minute recovery.Altitude, phase, and altitude × phase effects were significant (all p < 0.001).The overall HR group effect was nonsignificant (p = 0.053), but the group × altitude × phase interaction was significant (p = 0.010).Lactate reached its highest sampled mean at three minutes and remained elevated at 30 minutes.Sprinters showed higher post-exercise and recovery concentrations.Lactate showed significant group, altitude, and time effects (all p < 0.001) and all two-way interactions, but no significant three-way interaction (p = 0.123). ConclusionsAcute simulated altitude increased desaturation, cardiovascular strain, and post-exercise lactate concentrations.Group differences were clearer for lactate than for overall SpO₂ or HR, but cannot be attributed solely to training background or slower lactate clearance.Combined physiological assessment and serial lactate sampling may support more informed monitoring of exercise responses under acute hypoxia.