The purpose of this study was to investigate the tendency of injuries and physical characteristics in junior high school soft tennis players and clarify the characteristics of movements associated with the cause of injuries. A total of 20 players(16 males and 4 females) were involved in the study and were divided into the Injury group(n=11) and the Non-injury group(n=9) based on a medical history questionnaire. One person from each group was selected considering their position and handedness, and their forehand stroke motions were recorded using a 3-D motion analysis system. The joint angle was determined from the calculated three-dimensional coordinates. During the swing, participants in the Injury group started the joint movement in the order of trunk, lower extremity, and upper extremity; whereas those in the Non-injury group started the joint movement in the order of lower extremity, trunk, and upper extremity. In the forehand stroke, rotational energy is mandatory to be transmitted from the lower limbs to the trunk and then to the upper limbs for generation of effective swing velocity. It was suggested that deviation from this transmission pattern of the rotational energy could be one of the factors causing the injury.
