VENTILATORY SENSITIVITY TO CARBON-DIOXIDE - THE INFLUENCE OF EXERCISEAND ATHLETICISM

Endurance training reduces the ventilatory response to a given level o f work, and there is evidence that endurance athletes possess attenuat ed chemosensitivity at rest; but it is unclear whether attenuation per sists during exercise. We compared the carbon dioxide sensitivity (S) of endurance-trained (ETG), sprint-trained (STG), and control subjects (CG), at rest and during cycle ergometry. Steady-state carbon dioxide (CO2) inhalation was employed; ventilatory parameters were measured u sing an ultrasonic flowmeter linked to a computer. CO2 concentrations were measured at the mouth using an infrared CO2 analyzer or mass spec trometer. Mean resting CO2 sensitivity of the ETG was significantly lo wer than that of the STG (P < 0.05), but not the CG (P < 0.058). S inc reased from rest to exercise in all endurance-trained subjects, but th e responses of the STG and CG were varied. Compared to rest, mean S wa s significantly higher during exercise for the ETG, but not for the ST G or CG. S was the same in all groups during exercise. During air brea thing exercise all subjects were mildly hypercapnic. The ETG showed th e greatest rise in mean alveolar PCO2, but this could not be attribute d to attenuated chemosensitivity since responsiveness during exercise was identical in all three groups.