In order to clarify pitching mechanism for the progress of pitching performance and the achievement of more long-running career, pitching motions of 2 professional baseball pitchers were analyzed biomechanically using motion capture system and floor force plates. One (pitcher A) is in his 28th year on the active list, and the other (pitcher B) is in his second year on the active list. Both are in the first team. As a result, pitcher A pitched using leg, torso and pitching arm in sequence concentrically. This mechanism was named "triple step rocket system". However pitcher B pitched using only leg and pitching arm concentrically. These differences were quantified through energetic analysis, called "distribution ratio of joint concentric energy". Then we defined "pitching efficiency" as a ratio of kinetic energy of the ball pitched to summation of whole body energy produced in pitching motion. The ball speed of pitcher B was faster than that of pitcher A, nevertheless the pitching efficiency of pitcher A were better than that of pitcher B. These results were caused by the difference of the movement of torso between both pitchers. This shows that torso rotation is important to pitching mechanism.
