Alterations in ventilation and gas exchange during exercise-induced carbohydrate depletion

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Abstract
The relationships between ventilation , oxygen consumption , and carbon dioxide production during work were studied in four trained males during exercise-induced carbohydrate depletion. Repeated bouts of heavy treadmill exercise (6 min at 95% max) were performed once per hour for 24 h in order to promote a shift in energy substrate from carbohydrate to fat. Measurements of and recorded during each minute indicated that was unaffected by the number of runs, whereas showed a progressive reduction which amounted to 24% during the final run. A corresponding decline of 19% was observed in the respiratory exchange ratio. No significant change in occurred between any of the runs. It is concluded that during heavy, repeated, muscular exercise, reductions in , strongly suggestive of an increased fat oxidation, are not accompanied by a corresponding change in ventilation.