抄録
During exercise, oxygen must be taken out of the air and sent to the exercising muscles, and carbon dioxide derived from metabolism must be discharged quickly from our bodies. Otherwise, acid-base and/or blood gases homeostasis will be lost and exercise cannot be continued. Accordingly, ventilation should increase quickly and precisely in accordance with metabolic demand during exercise (Exercise Hyperpnea). It is recognized that the chemoreceptor reflex should keep the tension of blood gases fixed thus maintaining homeostasis. However, during moderate constant load exercise blood gases are kept at nearly the same levels as during rest although ventilation markedly increases. The alternating mechanisms for exercise hyperpnea are assumed to be two neural pathways, central command and peripheral neural reflex. These neural mechanisms should operate from the onset of exercise so that ventilation increase rapidly and roughly before the metabolic byproducts reach the carotid body. Thus, the neural mechanisms are indispensable in the maintenance of homeostasis during exercise.The initial ventilatory response to exercise within 20s at the start of exercise, named Phase I, is derived solely from neural origin suggesting that to investigate Phase I response is very valuable for better understanding of exercise hyperpnea and its contribution to homeostasis. Our laboratory has been focused on Phase I and in this symposium I will introduce the accumulated data concerning the characteristics of Phase I in various subject groups (e.g. elderly, athletes etc.) and conditions (e.g. bedrest, muscle soreness etc.). [J Physiol Sci. 2007;57 Suppl:S51]
