The muscle glycogen is an important energy source for muscle contraction especially in prolonged exercise. One of the important factors for improvement of physical performance in athletes is the storage of extra-amount of glycogen (supercompensation) in liver and muscles. During 120 minutes treadmill exercise (intensity of exercise was approximatly 80% VO2max), the glycogen concentration was significantly decreased to 36% in liver and 46% in muscles after 60 minutes exercise. At 90 and 120 minutes of exercise, the level of glycogen concentration of liver and muscles statistically were not different from the levels of the 60 minutes exercise. The repletions of glycogen in the liver and muscles in overnight fasted control(C) and 120 minutes treadmill exercise(E) groups during l80minutes after glucose ingestion were investigatect. ln the liver, the concentration of glycogen in C and E groups were markdly increased till 120 minutes after zlucose ingestion, hut the levels of concentration at 180 minutes were decreased comparing to the levels of 120 minutes in both groups. In the muscles, the repletion of glycogen at 60, 120 and 180 minutes of C and E groups were significantly increased comparing to 0 minute of respective groups in the soleus and plantaris muscles. In soleus(SOL), the repletion of glycogen in all of the E groups was significantly higher than that of the respective C groups. However, the repletion of glycogen in all of the E groups of plantaris was revealed higher tendency comparing to respective C groups. Mean repletion rates of glycogen in liver and muscles after glucose ingestion were highest during the first 60 minutes in all groups and the rates of E groups were 2-3 times than those of respective C groups. These results suggest that the glycogen supercompensation in the muscle be provided with decrement of glycogen concentration by exercise, increment of glucose uptake by muscuiar contraction itself and increased insuJin level, and the activation of glycogen synthetase by insulin.