Changes in glenohumeral range of motion by repetitive pitching and their relationship with arm speed during pitching

This study aimed to (1) examine the acute changes in the glenohumeral range of motion (ROM) after repetitive pitching and (2) clarify whether arm speed during pitching is associated with changes in the glenohumeral internal rotation (IR) and horizontal adduction (HADd) ROM. Fifteen healthy college males with over five years of baseball experience participated. Glenohumeral ROMs of IR, external rotation, and HADd were measured using a digital inclinometer before, immediately after, and one day after completing 100 repetitive full-effort pitches. Arm speed during pitching was measured using wearable inertial measurement unit sensors. IR ROM significantly decreased immediately after (p < 0.001) and a day after (p = 0.043) the pitching task compared to the baseline values. HADd (p = 0.361) and external rotation (p = 0.935) ROM exhibited no changes between pre-and post-pitching. Changes in the IR ROM were associated with arm speed during pitching (β = -0.728, p = 0.002 for pre-post change; β = -0.645, p = 0.009 for pre-post one-day change). Our findings imply that reductions in the glenohumeral IR ROM may precede chronic adaptations of the throwing shoulder. Furthermore, arm speed during pitching was a predictive factor for the changes in the glenohumeral IR ROM.