A Repeated-Measures Study: Does Acute Exposure to Simulated Moderate Altitude Alter Wingate Performance and Skeletal Muscle Oxygenation Differently in Sprinters and Middle- and Long-Distance Runners?

BACKGROUND: Acute hypoxia may preserve initial explosive power while impairing power maintenance. This study examined graded acute simulated altitude effects on Wingate performance and vastus lateralis oxygenation in sprinters and middle- and long-distance (MD/LD) athletes. METHODS: Forty-four Indian sub-elite athletes, comprising 22 sprinters and 22 MD/LD athletes, completed a 30-second Wingate test under normoxia and simulated altitudes of 2000 m and 3000 m. At least 72 hours separated the trials. Muscle oxygenation was assessed using near-infrared spectroscopy. Data were analyzed using 2×3 mixed-design repeated-measures analysis of variance, Bonferroni-adjusted comparisons, and Spearman correlations. RESULTS: At 3000 m, peak power decreased by 4.87-5.03%, average power by 7.24-9.84%, and minimum power by 11.78-15.72%. Power drop increased by 14.47-15.63%. Altitude significantly affected all Wingate outcomes (all p<0.001). The effects were largest for power drop (ηp²=0.972), minimum power (ηp²=0.954), and average power (ηp²=0.913), showing greater impairment of power maintenance. Group×altitude interactions were significant for average power (p<0.001), minimum power (p<0.001), and power drop (p=0.023), but not peak power (p=0.980). Oxygenated hemoglobin-myoglobin signal (O₂Hb), total hemoglobin (tHb), and tissue saturation index (TSI) decreased, whereas deoxygenated hemoglobin-myoglobin (HHb) increased (all altitude effects p<0.001; ηp²=0.950-0.998). At 3000 m, TSI was lower in sprinters than in MD/LD athletes (39.72±7.83% vs. 46.17±7.57%; adjusted p=0.025). Average power loss correlated with TSI change (ρ=-0.645; adjusted p<0.001) and HHb change (ρ=-0.707; adjusted p<0.001). CONCLUSION: Acute simulated altitude impaired power maintenance and fatigue resistance more strongly than initial explosive power. Changes in TSI and HHb were associated with average power loss, particularly at 3000 m. These correlations do not establish causality. Sprinters and MD/LD athletes showed different response patterns, but neither group demonstrated a consistent overall advantage. Average power, minimum power, power drop, and muscle oxygenation may be considered together when evaluating anaerobic performance under hypoxic conditions.