抄録
[Purpose] We studied the angular velocities of the trunk and upper extremities using a 3D analyzing system to analyse the throwing motion.
[Materials and methods] Ninety best pitches, which 34 baseball pitchers(14 professionals,5 semiprofessionals,15 high school players) threw, were examined. The throwing motions were recorded by two NAC high speed videos. The angular velocities between the two shoulders and the upper arms(shoulders), between the upper arms and the fore-arms (elbows), the fore-arms and balls(wrists), between the two shoulders and the pelvis (trunks) were calculated. Measurements were taken of the acceleration phase and the follow through phase.
[Results] The angular velocities of the trunk showed first the peak level during from 10% to 30% of the acceleration phase. Then, the peak levels of angular velocities successively improved in the shoulder (from 40% to 60%), the elbow and the wrist (from 80% to 100%).
In the follow through phase, the angular velocities of the shoulder increased again right after the ball release.
[Discussion] The throwing motion is based on the rotation in the throwing plane. According to our results, the rotational energy transferred smoothly from the proximal to the distal parts of the body, as shown in the changing peak levels of the angular velocities. We believe that pain or fatigue prevent an efficient energy transmission and this strain results in a throwing injury.
