Background: The understanding of the glenohumeral (GH) joint motion during baseball pitching should be necessary for diagnosis and treatment for throwing shoulder. The purposes of this study were firstly to investigate the motions of the scapula, pelvis, upper body, and upper limbs and secondly to speculate the motion of the GH joint and the scapula from the top position to ball release.
Methods: We observed the pitching of 2 professional and 2 high-level amateurs with a digital camera and a video camera, recording each motion of the pelvis, upper body, scapula, and upper limbs. We classified pitching motion into 3 phases which were slide, upper body rotation, and arm throwing in order to simply analyze the motion in each phase.
Results: Each scapula protracted and retracted respectively during pitching motion. The pelvis which was closed in the stride, ball release, and follow-through synchronized with scapular motion. The throwing arm moved in the scapular plane and made the elbow extend to the ball release. Internal rotation of the humeral head was a little from the top position to the ball release.
Discussion: Both scapula and pelvis synchronized at each phase of pitching motion. The motion of the GH joint was speculated to be a small amount from the top position to ball release.
