Abstract
The purpose of this study was to determine whether significant concentric strength and range of motion differences exist between the dominant and nondominant shoulders of highly skilled junior tennis players. Concentric isokinetic testing of 26 (12 male and 14 female, 11- to 14-year old) highly skilled tennis players was conducted using a Cybex 350 and UBXT. Tests were conducted bilaterally for shoulder internal and external rotation with 90 deg abduction at 60, 90, 210, and 300 deg/sec. Significantly greater (p < 0.005) dominant arm internal rotation strength was measured compared with the nondominant arm for boys at all four testing speeds for peak torque and best work repetition. No significant difference was found in external rotation at any speed for peak torque and best work repetition for boys. Bilateral comparisons also showed significantly greater (p < 0.05) internal rotation strength on the dominant arm of the girls at 60, 90, and 210 deg/sec for peak torque and at 210 and 300 deg/sec for best work repetition. No significant difference was measured for external rotation at any testing speed for peak torque or best work repetition. Significantly less (p < 0.05) goniometrically assessed internal rotation range of motion and greater (p < 0.05) external rotation range of motion was found on the dominant arm of the boys when compared with the nondominant extremity. The girls also had less (p < 0.05) internal rotation range of motion on the dominant arm, but did not have a significant difference between extremities in external rotation. Selective development of the internal rotators of the shoulder relative to the external rotators was found in the dominant arm of highly skilled junior tennis players at a very young age. The imbalance of strength found in this study is important to physical therapists in rehabilitation and design of specific conditioning programs for the upper extremity athlete.