ABSTRACT

　Hyperthermia during exercise leads to increases in ventilation independently of metabolic factors, resulting in hypocapnia and cerebral hypoperfusion. This study examined the effects of sleep deprivation on body temperature and cardiorespiratory responses during exercise in the heat. Six male subjects performed a cycle exercise at 50% of peak oxygen uptake in the heat (37℃ ambient temperature and 50% relative humidity) until their esophageal temperature (Tes) reached 39℃ or they could no longer continue the exercise. Normal sleep (control trial) or ~ 28h of wakefulness (sleep loss trial) preceded the exercise-heat test. Tes, minute ventilation (VE), respiratory gases, sweat rate (ventilated capsule method) and skin blood flow (laser-Doppler), heart rate and arterial blood pressure during the exercise were measured continuously. Exercise duration did not differ between trials (P>0.05). Tes at rest tended to be lower in the sleep loss than control trial, and it during exercise and at the end of exercise did not differ between trials (P>0.05). Plotting ventilatory and thermoregulatory responses against Tes showed that VE at Tes of 38.8℃ was higherin the sleep loss than control trial (P<0.05), and the sensitivity of VE to rising Tes (slope of the Tes-VE relation) tended to be greater in the sleep loss than control trial. Sleep loss did not affect the Tes thresholds for sweating and cutaneous vasodilation and the sensitivities of the responses (P>0.05). These results indicate that during prolonged exercise in the heat, sleep deprivation can accelerate hyperthermia-induced hyperventilation during prolonged submaximal exercise in the heat.

DESCENTE SPORTS SCIENCE Vol.38/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE