In the present study, we examined longitudinal changes in body size and fitness test records of high school students (males：n=16 ; females：n=6) who had been engaged in“Aikido”as their extracurricular activities from the 1st through the 3rd grade. The chronological changes of body size and and fitness test records were analyzed by repeated-measure analysis of variance at significant level of P＜0.05. Both the body size physical fitness of every subject were significantly improved throughout the three years. This led us to the conclusion that, by training in "Aikido"”throughout their high school years, even the subjects with poor body compositions at baseline showed conspicuous improvement compared with the standard levels of japanese high school counterparts. Another significant improvement was observed in their fitness test records , especially such components as flexibility, agility and grip-strength. Thus, our findings suggest that tge specific skill training in "Aikido", such as footwork,turnover of attack and defense, and‘kata’ (training of forms), might result in the improvement of fitness levels.