Hypoxia during supramaximal exercise reduces aerobic metabolism with a compensatory increase in anaerobic metabolism without affecting exercise performance. A similar response is elicited by preexercise voluntary hypocapnic
hyperventilation, but it remains unclear whether hypocapnic
hyperventilation and
hypoxia additively reduce aerobic metabolism and increase anaerobic metabolism during supramaximal exercise. To address that issue, 12 healthy subjects (8 males and 4 females) performed the 30-second Wingate anaerobic test (WAnT) after (1) spontaneous breathing in normoxia (control, ∼21% fraction of inspired O2 [FiO2]), (2) voluntary hypocapnic
hyperventilation in normoxia (
hypocapnia, ∼21% FiO2), (3) spontaneous breathing in
hypoxia (
hypoxia, ∼11% FiO2), or (4) voluntary hypocapnic
hyperventilation in
hypoxia (combined, ∼11% FiO2). Mean power output during the 30-second WAnT was similar among the control (561 [133] W),
hypocapnia (563 [140] W),
hypoxia (558 [131] W), and combined (560 [133] W) trials (
P = .778).
Oxygen uptake during the 30-second WAnT was lower in the
hypocapnia (1523 [318] mL/min),
hypoxia (1567 [300] mL/min), and combined (1203 [318] mL/min) trials than in the control (1935 [250] mL/min) trial, and the uptake in the combined trial was lower than in the
hypocapnia or
hypoxia trial (all P < .001).
Oxygen deficit, an index of anaerobic metabolism, was higher in the
hypocapnia (38.4 [7.3] mL/kg),
hypoxia (37.8 [6.8] mL/kg), and combined (40.7 [6.9] mL/kg) trials than in the control (35.0 [6.8] mL/kg) trial, and the debt was greater in the combined trial than in the
hypocapnia or
hypoxia trial (all P < .003). Our results suggest that voluntary hypocapnic
hyperventilation and
hypoxia additively reduce aerobic metabolism and increase anaerobic metabolism without affecting exercise performance during the 30-second WAnT.