Respiratory and blood gas responses in exercising birds.

The effects of exercise in birds on changes in body temperature, ventilation, blood gases and air-sac gases are reviewed. Except in the case of isothermic exercise below the anaerobic threshold, birds hyperventilate during exercise. Exercise hyperventilation is greater at higher exercise intensities and at higher environmental temperatures. The domestic fowl appears to be a suitable model for the study of physiological responses to exercise in running birds. A prior period of training is necessary to accustom the birds to laboratory procedures. The possible neural and/or humoral mechanisms controlling exercise hyperpnea are listed. Intrapulmonary hypocapnia seems to exclude the possibility that lung chemoreceptors are responsible for the hyperpnea during exercise, but these receptors probably play a predominant role in the determination of ventilatory pattern.