This study was aimed to investigate the relationship between the clinical symptoms around the scapula and kinematic differences of baseball pitches in overhand throwers.115 male baseball pitchers were measured with a motion capture system (ProReflexTM MCU-500+, Qualisys Inc, Sweden) after adequate physical examinations. The subjects were classified into the following two groups according to their tenderness around the scapula; group A: without pain (54 cases, mean age: 17 ± 5.4 years old, height: 1.7 ± 0.1 m, mass: 64 ± 13.3 kg), group B: with pain (61 cases, age: 17 ± 4.7 years old, height: 1.7 ± 0.1 m, mass: 64 ± 12.7 kg). The angular displacements of the shoulder, trunk, hip and knee were calculated during pitching motion. These parameters were compared between the two groups. T test was used for statistical analysis, and the p < 0.05 was considered to be significant. At the instant of front foot contact, abduction of the shoulder in group B was smaller than in group A (p < 0.05). At ball release, the trunk rotation and the horizontal adduction of the shoulder in group B were smaller than those in group A (p < 0.05). The hip of the throwing arm side in group B tended to be in adducted and internally rotated position rather than in group A. It is important to investigate the relationship between the clinical symptoms and the motion data of throwers for improving their performance. The results showed that the manner of pitch might have some relations with shoulder pain. In the clinical scene, it was suggested to mind the posture of baseball pitchers to prevent their shoulder pain.
