Proposal for the assessment protocols for different shoulder muscle groups

Abstract

Isokinetic dynamometers allow an accurate measurement of the strength developed by muscle groups surrounding different joints. Nevertheless, the particular shoulder complexity offers a great variety of testing positions and articular planes for the isokinetic examiners. Consequently, users must define valid protocols and determine the reproducibility of the main parameters. Because shoulder dysfunctions frequently affect the rotator cuff muscles, our study aimed at the elaboration of a reliable isokinetic assessment for the internal (IR) and external (ER) rotators and for the abductors (ABD) and adductors (ADD) in healthy subjects. Ten male and ten female subjects (average age respectively 42 ± 5 years and 40 ± 4 years) without history of shoulder pathology participated in the study. Shoulder IR and ER were assessed using a Cybex Norm dynamometer in 90 ◦ of abduction in the frontal plane, the subject being in a lying supine position, at 2 angular velocities (60 ◦ .s −1 , 240 ◦ .s −1 ) in the concentric mode. In order to avoid the elevation of glenohumeral joint and elbow flexion during classical assessment, we proposed an original position and adapted protocol for ABD and ADD muscles. The subject was in lying lateral position, arm in the frontal plane, with a range of motion limited to 90 ◦ of abduction. Great care was taken to correctly align the glenohumeral center joint with the dynamometer axis. The new protocol proposed two speeds in the concentric mode (60 ◦ .s −1 and 180 ◦ .s −1 ). For the reproducibility study, an interval of 10 days was inserted between the two sessions of measurement.