This study assessed the influence of muscle strength training in the immature period on training effect after maturity. Seven- weeks-old male Wister rats were used in each group (experimental and control group). The tenotomy method was used to create a model of muscle hypertrophy. The rats in the experimental group, were repeatedly injected with bupivacaine to activate a satellite cells in their muscle tissue.
　After three bupivacaine injections, the muscle weight of the bupivacaine experimental group was recovered to the muscle weight of the control group, and a tendon was then removed surgically. The muscle cells in the tissue of the control group were enlarged and exhibited muscle hypertrophy, and open spaces were observed in the perimysium and endomysium. Small cells with central nuclei, were observed in the perimysium and endomysium.
　Most muscle cells were newly generated after three bupivacaine injections. Most of the muscle fibers the contralateral muscle in the experimental group had central nuclei. In addition, enlarged cells formed by fusion between muscle cells were observed in the muscle tissue in the tenotomy side in the experimental group.
　The FGF was expressed in the muscles in the control group. and its expression increased with compensation load. In the experimental group, on the other hand, the level of FGF gene expression on the contralateral side was extremely decrerased, but it increased in response to a compensation load.
　Increases in plantaris and soleus muscle weight after maturity were compared in the group in which muscle hypertrophy was induced by tenotomy in the immature period and in the control group. The rates of increase in weight of the plantaris muscle, were significantly different between the two groups, and also there was a significant a socalled fast muscle, difference in the weight of soleus muscle, a so-called slow muscle, between the two groups.
　Muscle weight in the group of rats whose tendon was removed surgically in the immature period increased in response to compensatory load. The results of experimental 1suggested that activation of satellite cells in the immature period adversely affects muscle enlargement after maturity. However, no such results were obtained in this experiment. Future study is needed to elucidate the case.

DESCENTE SPORTS SCIENCE Vol.22/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE