Shoulder Rotators Isokinetic Profile According to Instability and/or Sport Specificity: Implications for...

To describe the shoulder rotator muscle profiles across healthy, unstable, and athletic contexts and compare the usual peak torque (PT) method and the angular range (AR) method.

Retrospective analysis of data collected cross-sectionally.

Hospital. Each participant participated in isokinetic evaluations of the shoulder rotator muscles at 60°/s (concentric/eccentric) for both shoulders.

A total of 239 participants with a mean age of 24.7 (7.5) years INTERVENTIONS: None.

We recorded the PT and AR mean torque by 10°, and we calculated the antagonist/agonist ratios. We used a 2-way repeated measures analysis of variance with a correction for multiplicity to compare laterality (ie, side-to-side) and contexts (ie, no-overhead sports healthy, no-overhead sports with unstable shoulder, overhead sports healthy, and overhead sports with unstable shoulder.

Concentric PT of external rotators were significantly lower in no-overhead athletes with shoulder instability than healthy no-overhead athletes (P=.007) and healthy overhead athletes (P=.029). The AR highlighted significant (P<.05) lower concentric external and internal rotator muscles strength: (1) in no-overhead athletes with shoulder instability than in healthy no-overhead athletes; (2) in healthy overhead athletes than in healthy no-overhead athletes; and (3) in no-overhead athletes with shoulder instability than in healthy overhead athletes. No significant difference was observed in the eccentric modality or in the PT/AR ratios. Significant side-to-side differences (P<.05) between dominant and nondominant sides were reported by both PT and AR methods.

Only the concentric muscle profiles differed across context groups. The AR allowed for a more precise detection of shoulder muscle adaptations by identifying unique muscle signatures in the moment-angle relationship. These 10° AR measurements offer complementary information and enhance the clinical utility of isokinetic profiling compared to the traditional PT method.