Among the baseball players, the shear forces on the shoulder at ball release can be significantly reduced by achieving 10.7° of horizontal shoulder adduction and 80.6° of shoulder abduction as per the study published in the ‘The American Journal of Sports Medicine.’

The baseball players during pitching experienced an intense anterior shoulder pain due to an excess joint reaction force on the shoulder and unrestrained shoulder horizontal abduction at ball release. Hiroshi Tanaka and colleagues conducted a descriptive laboratory study to evaluate an association between force on the shoulder while releasing the ball and horizontal abduction posture of the shoulder. The analysis also assessed the range of shoulder motion and relative rotational pose of the shoulder at ball release to reduce the force on the shoulder.

A total of 183 young baseball pitchers of 15.5 ± 1.2 years old who had no elbow/shoulder problems were selected. Overall five fastballs were thrown to a catcher behind the home plate by every pitcher. The 3-dimensional measurements from 36 reflective markers were used to assess kinetics and kinematics of the shoulder, which is used to pitch the ball. The association between forces on the shoulder (proximal, superior-inferior and anterior-posterior) and relative rotational postures of the shoulder (horizontal adduction-abduction and abduction) at the time of releasing the ball was also determined. The range of motion and particular rotational position, which subsequently reduces the forces on the shoulder, were also evaluated.

The magnitude of anterior-posterior and superior-inferior forces on the shoulder showed a statistically significant relationship with horizontal adduction-abduction and abduction position of the shoulder respectively  .001). The least superior-inferior and anterior-posterior forces were noticed with the combination of 10.7° of horizontal adduction and 80.6° of shoulder abduction. Both superior-inferior and anterior-posterior forces got increased considerably in case of any >5° deviation from above noticed the least value of forces. These results might be helpful to reduce and prevent shoulder pain.