Fig. 2

Comparisons of cardiorespiratory parameters between normoxia and hyperoxia on each gradient. a SpO₂ on the level and b uphill gradient. c V_E on the level and d uphill gradient. e P_ETCO₂ on the level and f uphill gradient. g \( \dot{V}{\mathrm{O}}_2 \) on the level and h uphill gradient. i \( \dot{V}{\mathrm{CO}}_2 \) on the level and j uphill gradient. k HR on the level and l uphill gradient, respectively. Open circles and squares represent walking under normoxia and hyperoxia. Filled circles and squares represent running under normoxia and hyperoxia. To avoid overlapping plots at each speed, normoxic and hyperoxic data were plotted 0.1 km h⁻¹ slower or faster than the actual speeds. ⁺p < 0.05, ^*p < 0.01, and ^#p < 0.001 between normoxia and hyperoxia