Functional activity characteristics of individuals with and without shoulder disorders

Objective. To test the reliability of three-dimensional shoulder complex movements during functional tasks, and to compare motion patterns between two groups.; Design. Within-session intraclass correlation coefficients (ICC) and standard error of measurement of the kinematic and electromyographic (EMG) data during the 5 functional tasks were calculated. Two-way repeated analyses of variances were used to determine any difference existed between the two groups.; Background. Evaluating functional activities is a key concern for a clinician in the diagnostic assessment, outcome measurement, or planning treatment programs of patients.; Methods. The dominant right arms of 25 asymptomatic male subjects, 30–82 years old; and 25 male subjects with shoulder disorders, 27–80 years old, were assessed, using a 3-D electromagnetic movement recording system and an EMG system.; Results. Good within-session reliability was found across the 5 tasks in both groups (ICC = 0.63 to 0.99). The standard error of measurement was equal to or less than 2.5 degrees or 0.4 centimeters for all kinematic variables across the 5 tasks in both groups. The standard error of measurement was less than 3.5% maximal voluntary contraction (MVC) for all EMG muscular activities across the 5 tasks except for the serratus anterior muscle in one task (7.7% MVC). Relative to the group without shoulder disorder, the group with shoulder disorder showed decreased scapular posterior tipping across the 5 functional tasks, increased scapular elevation in two tasks, decreased scapular upward rotation in one task, decreased humeral elevation in one task, and decreased humeral lateral rotation in one task. At the same time, upper trapezius and anterior deltoid muscle electromyographic activity increased in the group with shoulder disorder as compared with the group without shoulder disorder in five and two tasks respectively. The serratus anterior muscle demonstrated decreased activity in the group with shoulder disorder in three tasks.; Conclusions. The 3-D shoulder complex kinematics and associated muscular activities during the functional tasks can be reliably quantified by the motion analysis and EMG systems in individuals with and without shoulder disorders. Scapular tipping, upper trapezius muscle function, and serratus anterior muscle function may have implications in the rehabilitation of patients with shoulder disorders.