Internal- and External-Rotation Peak Torque in Little League Baseball Players With Subacromial Impingement Syndrome: Improved by Closed Kinetic Chain Shoulder Training

Context: Many studies have explored closed kinetic chain (CKC) shoulder exercises (SEs) with a sling because they are safer and more effective than open-chain exercises, especially in early stages of treatment. However, the application of CKC SE in youth baseball players has rarely been attempted, although teenage baseball players also experience shoulder pain. Objective: To investigate the effects of CKC SE on the peak torque of shoulder internal rotation (IR) and external rotation (ER) in youth baseball players. Design: Single-group pretest, posttest. Setting: Biomechanics laboratory. Participants: 23 Little League Baseball players with subacromial impingement syndrome. Interventions: The CKC SE with a sling was CKC shoulder-flexion exercise, extension exercise, IR exercise, and ER exercise. This exercise regimen was conducted 2 or 3 times/wk for 8 wk. Main Outcome Measures: The peak torque of shoulder ER and ER was measured using an isokinetic dynamometer. Concentric shoulder rotation was performed, with 5 repetitions at an angular velocity of 60 /s and 15 at 180 /s. Results: The IR and ER peak torque significantly increased at each angular velocity after the exercise program. In particular, the increase in IR and ER peak torque values was statistically significant at an angular velocity of 180 /s. Conclusions: CKC SE was effective in increasing shoulder IR and ER strength, demonstrating its potential benefits in the prevention and treatment of shoulder injury. In addition, increased IR peak torque appears to improve throwing velocity in baseball players.