Bicarbonate infusion and pH clamp moderately reduce hyperventilation during ramp exercise in humans

1 Département de Kinésiologie, Université de Montréal, Montréal, Quebec, Canada; 2 Institute of Sports and Preventive Medicine, University of Saarland, Saarbrucken, Germany; and 3 Laboratoire de Physiopathologie de l'Exercice, HYLAB, Clinique du Mail, Grenoble, France Submitted 17 May 2006 ; accepted in final form 28 August 2006 ABSTRACT To test the hypothesis that the decrease in plasma pH contributes to the hyperventilation observed in humans in response to exercise at high workloads, five healthy male subjects performed a ramp exercise [maximal workload: 352 W (SD 35)] in a control situation and when arterialized plasma pH was maintained at the resting level (pH clamp) by intravenous infusion of sodium bicarbonate [129 mmol (SD 23), beginning at 59% maximal workload (SD 5)]. Bicarbonate infusion did not modify O 2 consumption ( O 2 ) but significantly ( P < 0.05) increased arterial P CO 2 , plasma bicarbonate concentration, and respiratory exchange ratio ( P < 0.05). At the three highest workloads, pulmonary ventilation ( E ) and E / O 2 were 5–10% lower ( P < 0.05) when bicarbonate was infused than in the control situation, and hyperventilation was reduced by 15–30%. These data suggest that the decrease in plasma pH is one of the factors that contribute to the hyperventilation observed at high workloads. ventilatory threshold; lactate; acid-base balance; chemoreceptors Address for reprint requests and other correspondence: F. Péronnet, Département de Kinésiologie, Université de Montréal, CP 6128, Centre Ville, Montréal, QC, Canada H3C3J7 (e-mail: francois.peronnet{at}umontreal.ca )