Isokinetic assessment of the shoulder rotators: a study of optimal test position

P>Background: Isokinetic assessment of the shoulder rotator cuff is a common component of shoulder muscles assessment. Nevertheless, the extensive mobility of the shoulder poses great difficulty in finding a consensus protocol for evaluation. Objective: To select an optimal protocol, among three, based on the best reproducibility and reliability of strength scores derived from internal and external rotator tests. Method: The dominant side external and internal rotator muscles of twelve healthy male subjects were evaluated based on a concentric protocol (60 degrees s-1 and 240 degrees s-1) in three different test positions: two in lying supine with the arm in either 90 degrees or 45 degrees abduction and one in the seated position with the arm moving in the scapular plane on the dominant shoulder. Subjects were tested twice over 10 days. Results: The two lying installations were associated with the lowest coefficient of variation (7 center dot 1-11 center dot 8%) and smallest detectable difference (7-15 center dot 9 N center dot m) for peak moment and strength ratios. Consequently, the lying positions were chosen for rotators assessment with 90 degrees of abduction associated with a higher reproducibility for the agonist/antagonist ratios or 45 degrees if some pain was provoked. In any case, the coefficient of variation did not exceed 12%. Conclusion: Based on a reproducibility and reliability analysis, we recommend the testing of isokinetic strength of the shoulder rotators to be conducted in supine lying, with the arm at 90 degrees or 45 degrees abduction in the frontal plane.