Isokinetic scapular muscle performance in overhead athletes with and without impingement symptoms

Context: Overhead activities such as throwing, tennis, or volleyball place athletes at considerable risk for overuse injuries. A relationship between scapulothoracic muscle imbalance and shoulder pain has been suggested. Objective: To compare the isokinetic muscle performance of the scapular muscles between overhead athletes with impingement symptoms and uninjured overhead athletes and to identify strength deficits in the patient population. Design: A repeated-measures analysis of variance with 1 within-subjects factor (side) and 1 between-subjects factor (group) was used to compare strength values and agonist:antagonist ratios across sides and across groups. Setting: University laboratory. Patients or Other Participants: Thirty overhead athletes with chronic shoulder impingement symptoms and 30 overhead athletes without a history of shoulder pain. Intervention(s): A linear protraction-retraction movement in the scapular plane at 2 velocities (12.2 cm/s and 36.6 cm/s). Main Outcome Measure(s): Isokinetic strength values and protraction:retraction ratios for both velocities. Results: Overhead athletes with impingement symptoms showed decreased force output:body weight at both velocities in the protractor muscles on the injured side compared with the uninjured side (−13.7% at slow velocity, −15.5% at high velocity) and compared with the control group at high velocity (−20.7%). On both sides, the patient group had significantly lower protraction:retraction ratios than the control group, measured at slow velocity (nondominant = −11%, dominant = −13.7%). Conclusions: Overhead athletes with impingement symptoms demonstrated strength deficits and muscular imbalance in the scapular muscles compared with uninjured athletes