Clinical shoulder measurements related to joint loads in collegiate pitchers

Abstract

Background: Pitchers are prone to upper extremity injury due to repetitive high joint loads. Clinical measures of shoulder strength and range of motion (ROM) have shown links to injury risk in pitchers, however, these factors have rarely been studied in relation to throwing joint loads. The purpose of this study was to identify which clinical ROM and isokinetic strength variables were related to peak shoulder and elbow joint torques in collegiate pitchers. Methods: Thirty-three healthy collegiate pitchers participated in this study. Fastball velocity, shoulder concentric and eccentric strength, and passive shoulder ROM variables were analyzed using a Lasso regression to determine what factors influenced shoulder internal rotation torque and elbow varus torque. Results: Fastball velocity was selected by the Lasso as indicator of increased shoulder and elbow torque. Passive shoulder external rotation ROM was also selected as an important factor in joint loading with increased shoulder external rotation ROM being related to lower joint loads. The bilateral ratio of shoulder internal rotator concentric strength was related to peak shoulder and elbow torques with an increase in the bilateral ratio of shoulder strength leading to reduced joint torques. Increases in the eccentric external rotator to concentric internal rotator strength (functional ratio) of the dominant arm and increases in dominant arm eccentric internal rotator strength were both related to increases in each joint torque. Conclusion: Results from the study indicate that pitch speed, passive shoulder external rotation ROM, and the isokinetic shoulder strength profile including internal rotator strength and functional strength ratio of pitchers are related to joint loading during the pitch and may be important to monitor in relation to injury risk and/or during rehabilitation. These results provide insight into the role that both shoulder ROM and rotator cuff strength play in the dynamic stabilization of the elbow and shoulder during pitching.

Keywords

• Baseball
• Range of motion
• Isokinetics
• Lasso regression
• Rotator cuff
• Torque