In 9 healthy young male subjects, cardiorespiratory responses during sinusoidal exercise were examined with or without whole body precooling. The work rate varied sinusoidally between 10% and 60% levels of oxygen uptake reserve at a 2-min period for 30 min. The decrease in mean body temperature of about 1.4℃ was observed by precooling for 1 hour by using a water perfused suit. The averaged, maximal, and minimal values, magnitude of response (difference between maximal and minimal values), and phase lags at the top and bottom of the work rate (ΔTz and ΔTn, respectively) were measured in each exercise cycle for cardiorespiratory parameters. The progressive increase in magnitude of response in oxygen uptake was delayed as a result of precooling. This phenomenon might be of peripheral origin. Based on findings of respiratory sinus arrhythmia response, an index of cardiac parasympathetic activity during sinusoidal exercise was introduced and it was suggested that cardiac parasympathetic activity tends toward greater fluctuation with a higher maximal level after precooling. Furthermore, whole body cooling before exercise tends to increase the ΔTz in the rate of perceived exertion, and might cause the decline in perceptual capacity of the change in work rate at a higher work rate.

DESCENTE SPORTS SCIENCE Vol.27/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE