抄録
Five trained (long distance runners) and five untrained subjects tried to run on a treadmill at the relative intensity of 70% Vo_2 max for two hours, while blood samples were taken at 30min intervals. Three untrained subjects, however, gave up on the way after 90min of running because of exhaustion. Plasma norepinephrine (NE) level was higher in the trained group (3.6±0.8ng/ml) than in the untrained group (2.2±0.7ng/ml) at 30 min of the exercise. Thereafter, NE in the former stayed almost constant in contrast to gradual increase in the latter. Taken as a whole the NE level during exercise was almost same between two groups. Plasma epinephrine (E) level in both groups elevated gradually in accordance with time course of exercise. However, the degree of increase was more rapid in the untrained group, which resulted in significantly higher E (2.7±1.4ng/ml) compared with the trained group) (0.9±0.3ng/ml) at 90min of the exercise. On the other hand, lower respiratory exchange ratio, lower serum lactate, higher serum glucose and higher serum free fatty acid were attained in the trained group during exercise. Significantly negative correlations were observed between plasma E and serum glucose at 30min (r=-0.856,P<0.01) and 90min (r=-0.893, P<0.01) of the exercise; Plasma E increased exponentially when serum glucose decreased below the resting level. Therefore, high response of E in the untrained group to the exercise was considered mainly to be due to lower level of blood glucose caused by greater level of untilization of carbohydrate as the energy fuel.
