[Importance of chemoreceptor stimuli to the speed of switching the respiratory response to exertion on and off].

The magnitude of the exercise respiratory response and its switch on and switch off rates were studied in 12 normal men breathing different gas mixtures. It was shown that hypercapnic stimulus reinforced and accelerated the respiratory response to exercise. Hypoxic stimulus mostly resulted in the increased though transient changes in the ventilatory rate at the start and at the end of exercise. This effect seems likely to be mediated by the fast-responding arterial chemoreceptors.