Yoshio Kuroda

Effect of alteration of peripheral blood flow on the central circulation in man during supine cycling in different ambient temperatures

SummaryWhether the alteration of peripheral circulation caused by changing ambient temperature (Ta) affects central circulatory changes in man during supine cycling was investigated in four well-trained men, who exercised at two levels (117.7 or 176.6 W). Exercise metabolic rate (VO2) in cold (0‡ C or 10‡ C) was the same as it was at 20‡ C, whereas the cardiac output (CO; CO2 rebreathing technique) and heart rate were significantly lower (e.g., 176.6 W at 0‡ C, both p<0.01). In heat (30‡ C or 40‡ C), the VO2 reduced with falling CO and mean arterial blood pressure from those at 20‡ C (e.g., 176.6 W at 40‡ C, all cases p<0.01), whereas the peak post-exercise calf blood flow (CBFp) increased (p<0.01). The VO2 and stroke volume (SV) were inversely proportional to the ratio of CBFp to CO/kg body weight (CBFp/CO) (r>−0.78, p<0.001). Total peripheral resistance (TPR) was related to arteriovenous oxygen difference (A-VO2 difference) (r>0.78, p<0.001). The TPR and A-VO2 difference decreased as Ta rose, while CBFp/CO was almost the same. As CBFp/CO had exceeded 50 and further progressed, however, the two parameters elevated until the same level as that at 0‡ C. The present results suggest that during moderately prolonged (16–60 min) supine cycling in different Tas the central circulatory changes are mainly affected by the altered peripheral blood flow in competing between skin and muscle for blood flow.

Strenuous Exercise Electrocardiogram of Top Class Swimmers in Mexico City

The effect of strenuous exercise (60 knee bends in 1min.) on the electrocardiogram was studied in 8 top class swimmers in Mexico City (altitude 2, 240M.). The electrocardiographic changes during the 3 week Mexico training were compared with the responses in Tokyo.(1) Heart rate immediately after the exercise increased markedly on the second day in Mexico, and declined gradually. Heart rate before and immediately after the exercise remained at higher level during Mexico training than in Tokyo.(2) Average amplitudes of P waves before and after the exercise in lead II were taller during Mexico training than in control study in Tokyo, the most prominent P waves after the exercise being observed on the second day in Mexico. P pulmonale at rest was observed in 2 cases. Right axis deviation of P waves was observed in 3 cases. These changes in heart rate and P waves returned to the control value after coming back to Tokyo.(3) Amplitude of T waves in lead II decreased immediately after the exercise throughout the study. Decreased amplitude of T waves before and after the exercise was remarkable after 12 days of Mexico training.(4) The junctional depression of ST segment after the exercise was remarkable in the first week of Mexico training, and disappeared gradually in the following week.(5) Relative QT duration was increased 2 and 5min. after the exercise. Relative QT duration increased during the Mexico training both before and after the exercise.These electrocardiographic changes during Mexico training and anginal chest pain experienced during and after the race indicated the need for the careful health examination of the athletes.