Concentric and Eccentric Isokinetic Rotator Cuff Ratios in Skilled Tennis Players

Abstract

Kevin Kennedy, PT, ATC* • David W. Altchek, MDt Irving V. Glick, MD=I= Hospital for Special Surgery, New York --------------------. -------------------The purpose of this study was to compare the concentric and eccentric strength of the internal and external rotators in skilled tennis players. Isokinetic testing of 62 male and female tennis players (Volvo levels 4-5 through 6-0) was performed on a LIDO Active Isokinetic System. Tests were conducted bilaterally for concentric internal and external rotation at 60 deg/sec, and for concentric and eccentric external rotators at 150 deg/sec. The concentric isokinetic testing of the dominant side at 60 deg/sec showed an external rotation to internal rotation ratio of 0.67 for average work per repetition. On the nondominant side, the ratio was 0.77. This difference represents a statistically significant difference in the work of the internal rotators in the playing arm. When tested at 150 deg/sec concentrically and eccentrically for the external rotators, it was found that the eccentric to concentric ratio was 1.46 for the average work per repetition on the dominant side. On the nondominant side, the ratio was 1.19. This difference represents a statistically significant difference in the work performed by the external rotators eccentrically. It was also determined that on the playing arm the external rotators' torque ratio, eccentric to concentric, was 1.43. From our data it was concluded that when measured eccentrically, the external rotators of the dominant arm were significantly stronger than those on the nondominant arm.