The oxygen cost and hyperlactatemia of voluntary hyperventilation during exercise

The effects of hyperventilation during exercise were studied with 4 healthy subjects. After an initial training period, each subject exercised on a bicycle ergometer at a workload requiring 70% of maximal aerobic capacity (v0_max) for 20 minutes. At least 4 test rides were performed: 2 control and 2 hyperventilation work bouts. . Voluntary hyperventilation occurred during min 10-20 of hyperventilation rides, following a l0-min control period. Subjects attempted to double pulmonary ventilation by increasing frequency and maintaining tidal volume, and to produce a decrease of end-tidal PC02 to 20-30 mm Hg. Post-exercise blood samples were taken to determine lactate concentration. Pulmonary minute volume (VI), 02 uptake (V02), C02 production (vCO2), respiratory exchange ratio (R), heart rate (HR), and lactate data were compared between control and hyperventilation periods. Over a VI range of 58-103 1/min, a mean O2 cost of 2.9 ml/l accounted for an average 7% of total VO2. The range of 02 costs was 0.2-5.2 ml/1. VC02, R, and HR also increased with hyperventilation, as did post-exercise lactate levels, the latter increasing by 53% with hyperventilation.

cost and lactate concentration. The metabolic consequences of hyperventilation do vary among subjects, perhaps according to the degree of acid-base changes associated with respiratory alkalosis.