Effects of constitution and physical training for obesity were investigated. 17 nature-excessively fat and 9 non-obese Wistarstrain male rats were bred at the room temperature of 23.0±1°C and humidity of 60% and fed ad libitum from 3 to 14 weeks after birth. At 4 weeks after birth, excessively fat rats were separated two groups. the former was loaded by motor driven treadmill for 8 weeks at a speed of 25 m/min for less than 15 min once daily and 6 times in a week. The latter was not loaded. Their running ability and basal metabolism were measured at 14 weeks after birth. Furthermore, weight of ventricle, liver and skeletal muscle (tibialis anterior, extensor digitorum longus, soleus, plantaris and gastrocnemius) on all groups were measured. Results are as follows.
　1. Body weight of excessively fat rats were more heavy at rate of 10% than control rats. Rates of muscle weight to body wight were lower, especially tibialis anterior and soleus were lower significantly (p<0.007, p<0.001, respectively). On the contrary, the rate of liver weight to body weight was more heavy significantly (p<0.001) than control, and its ratio are 1.5-1.7 fold.
　2. It seems that basal metabolism of the excessively fat rats were lower than the control rats, according to their low rate of muscle weight to body weight.
　3. Running ability of excessively fat rats showed 2.7 fold increase compared with those of non-loaded rats by physical training. It seems to increase basal metabolism on training rats as the result of the rised relative weight of ventricle and muscle to body weight.

DESCENTE SPORTS SCIENCE Vol.7/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE