Figure 1.

Comparison of ventilation (A), ventilatory equivalent for carbon dioxide ($\dot{\text{V}}$_E/$\dot{\text{V}}$CO₂) (B), end-tidal CO₂ (C), and arterial oxygen saturation (D), all plotted against oxygen uptake, during incremental cycle exercise in healthy young and older adults. Values are mean ± SEM. ^*P < 0.05 healthy young versus older adults. P_ETCO₂, partial pressure of end-tidal carbon dioxide; SpO2, oxygen saturation by pulse oximetry. Reproduced with permission from the publisher (Faisal et al., 2015).