VENTILATORY RESPONSES TO CO2 REBREATHING AT REST AND DURING EXERCISE IN UNTRAINED SUBJECTS AND ATHLETES

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Abstract
Ventilatory responses to CO2 during rest and exercise were studied in 10 marathon runners and 14 untrained subjects by the rebreathing method. The average responses of the untrained subjects and athletes at rest as measured by the slope of .ovrhdot.VE-PACO2 [pulmonary ventilation-alveolar CO2 partial pressure] curves were 1.86 and 1.12 l/min .cntdot. mmHg, the difference being statistically significant (P < 0.05). During exercise the slope of .ovrhdot.VE-PACO2 decreased from 1.86 to 0.62 in the controls, and from 1.12 to 0.62 in the athletes (.PI. < 0.01). The mean slope obtained in the athletes, at rest and during exercise, was .apprx. 50-60% of that in untrained subjects (P < 0.05). The difference in the .ovrhdot.VE-PACO2 curves between the athlete and the untrained group may be due to a reduced excitability of the respiratory center and/or by a reduced input signal.