Test-retest reproducibility of concentric strength values for shoulder girdle protraction and retraction using the Biodex isokinetic dynamometer

The aim of this study is to determine the rest-retest reproducibility for measuring the peak torque and the total work of the protractors and retractors of the shoulder girdle according to the isokinetic concentric muscle action. The tests were performed in two sessions at a 7 day interval. Nineteen healthy volunteers were included. Evaluation was carried out with a Biodex((R)) System 3 isokinetic dynamometer using the closed chain attachment. The protocol consisted of 5 isokinetic concentric contractions at a linear velocity of 12.2 cm/sec and 10 repetitions at a velocity of 36.6 cm/sec. The shoulder girdle protraction and retraction movements were performed with the arm horizontal in the scapular plane, which is 30 anterior of the frontal plane. Intraclass-Correlation-Coefficients were calculated to establish day-to-day repeatability. Results show an excellent reproducibility for isokinetic peak torque at both velocities on the non dominant side (ICC 0.94-0.96) and very good to excel lent reproducibility on the dominant side (ICC 0.88-0.92). Reproducibility was also very good for total work values in both movement directions at both velocities (ICC 0.82-0.89). The results indicate that isokinetic protraction and retraction strength evaluation is a reliable tool in the evaluation of shoulder girdle muscular performance. This may be clinically important in the assessment of shoulder dysfunction.