Do healthy subjects elevate and descend both arms in a same manner?

[Abstract]: Background. To determine whether or not healthy subjects elevate and descend their dominant and nondominant arms in the same manner is important in understanding the pathology of shoulder diseases: rotator cuff tear; impingement syndrome; stiff shoulder; and loose shoulder. Methods. Twenty young healthy subjects (17 males and 3 females, average age 24 years) were enrolled in this study. They randomly elevated and lowered both arms in the scapular plane 3 times and motion was measured using a three-dimensional motion analyzer. We calculated scapulohumeral rhythm in 10° increments and analyzed the setting phase during both elevation and lowering. Findings. There was no statistically significant difference in scapulohumeral rhythm between the dominant and nondominant arms. Scapulohumeral rhythm was stable (3.3) from 70 degrees during elevation to 70° in lowering; however, individual variations of scapulohumeral rhythm were identified, except for the previously described angles. The setting phase was identified as below 60° during elevation and a similar phase was also observed below 60° in lowering. There were two scapular motion patterns in the setting phase: the first started primarily as a scapular upward rotation; the second moved in the glenohumeral joint but less in the scapula. Interpretation. To elevate both arms in the same manner means that we can compare both the glenohumeral joint and scapular motion between affected and non-affected shoulders. The setting phase is defined as below 60° in elevation; moreover, a phase similar to the setting phase with variable scapular motion is identified during lowering.