Relationship between scapulothoracic joint angle during shoulder flexion and pitching motion at the late cocking phase

Abstract

Objective: This study aimed to evaluate the relationship between scapulothoracic joint (STJ) motion during pitching at the late cocking (LC) phase and shoulder flexion among baseball players.

Methods: This study recruited baseball players. Measurements during pitching and shoulder flexion motion were conducted using a three-dimensional motion device. The maximum STJ angles during pitching at the LC phase were calculated between timing of foot contact of the non-pivot leg and maximum shoulder external rotation (the LC phase). STJ angles during shoulder flexion motion were calculated from 30° to 120° of shoulder flexion (the raising and lowering phases). The relationship between each STJ angle during shoulder flexion motion and pitching was evaluated using Pearson’s correlation coefficient.

Results: The maximum value of STJ external rotation angle during pitching at the LC phase was significantly correlated with the STJ internal rotation angle of 90°(r＝0.314) and 120°(r＝0.300) during shoulder flexion at the raising phase. The maximum value of STJ posterior tilt angle during pitching was significantly correlated with SJT posterior tilt angle at 30° (r＝0.314) and 60°(r＝0.300) during the raising phase and SJT anterior tilt angle at 30°(r＝0.577) and 60°(r＝0.432) during the lowering phase.

Conclusion: This study found insufficient STJ posterior tilt and external rotation angle during late cocking of pitching motion correlated with insufficient posterior tilt angle of STJ and excessive internal rotation during shoulder flexion motion.