Functional activities characteristics of shoulder complex movements: Exploration with a 3-D electromagnetic measurement system.

The high prevalence of shoulder-related dysfunction has focused increased attention on functional activity assessment. This study (1) tested the reliability of three-dimensional shoulder complex movements during four functional tasks representing different levels of task difficulty, (2) characterized the four functional tasks, and (3) examined the relationships between age and shoulder movements. Twenty-five asymptomatic subjects, all veterans aged 30-82, performed the four functional tasks. Good within-session reliability was found (movement pattern: similarity index = 0.81 to 0.97, peak values: intraclass correlation coefficients = 0.88 to 0.99). The raising arm to overhead height task (hard task) placed the greatest demand on scapular motions and humeral elevation (p < 0.005). During the functional tasks, significant correlations existed between age and scapular tipping, humeral elevation, and scapular upward rotation (r = -0.62 to 0.50, p < 0.05). Correlation results indicated that elderly subjects have a greater potential for serratus anterior muscle weakness and shoulder capsule tightness.