We studied the effects of exercise on the blood fluidity. The subjects were 18 healthy males (21.6±0.8 yr, control : 5, soccer : 9, gymnastics : 4) . We measured the filtration time of whole blood by the Nuclepore filtration method as an index of blood fluidity. The filtration time at rest in the control group, soccer group, and gymnastics group was 59.8±11.9s, 42.5±15.1 s, 28.6±6.7s, respec tively. The filtration time at rest in the soccer group was significantly shorter than that in the control group (p<0.001) . There were no significant differences in filtration time at rest between the control and gymnastics groups, and between the soccer and gymnastics groups. The filtration time after single aerobic exercise was significantly prolonged compared with that before (p<0.001) . The filtration time before and after anaerobic exercise and muscular exercise was not significantly changed. The degree of filtration time prolongation was significantly lower in groups who drank water compared to groups who did not (p<0.001) . The effect of taking a sauna on filtration time was not significant. These results indicates the effect of aerobic exercise on blood fluidity, and the importance of water intake during exercise.

The aim of this study was to investigate the relationship between heart rate variability (HRV) during exercise and ventilatory threshold (VT), using the MemCalc system which is superior in spectral analysis. Nine healthy male subjects with no cardiopulmonary disease performed an exercise test to exhaustion to determine VT on a bicycle ergometer. Low frequency (LF : 0.04-0.15 Hz), high frequency (HF : 0.15-0.40Hz) and LF/HF ratio power spectra were calculated by maximum entropy method (MEM) spectral analysis, using the MemCalc system. In each case, when the subject started exercise, the HF component declined rapidly during the first 30 seconds ; and compared to the resting value, it declined to approximately 5 % at VT. The possibility of using this phenomenon as a criterion for setting intensity of exercise is tinder consideration. The LF/HF ratio showed different patterns of variation among the subjects. A significant linear relationship was seen between the declining rate of the HF component and VT (r=0.93, p<0.001), suggesting a corres pondence between the heart's capability of adjusting to maintained exercise and high endurance capacity.