Objective

To determine the electromyographical (EMG) activation levels of shoulder musculature during early rehabilitation exercises to regain active range of motion.

Design

Descriptive.

Setting

University clinical research laboratory.

Participants

Ten asymptomatic volunteers (age, 25 ± 5 years; height, 171 ± 7 cm; weight, 78 ± 15 kg).

Intervention

Fine-wire (supraspinatus and infraspinatus) and surface (anterior deltoid, upper trapezius, lower trapezius, and serratus anterior) electrodes recorded EMG activity from each muscle during 12 therapeutic exercises completed during a single testing session in random order.

Main Outcome Measure

EMG root mean squared amplitude normalized to a percentage of maximum voluntary contraction (% MVC).

Results

Passive exercises generated the lowest mean EMG activity (<10%) for all muscles studied. The standing active shoulder elevation exercises generated the greatest mean EMG activity with an upper boundary of 95% CI (40% MVC). Overall the active-assistive exercises generated a small (<10%) increase in muscle activity compared with the passive exercises for the supraspinatus and infraspinatus muscles, which was not a significant increase (P > .05).

Conclusion

This electrophysiological data in normal volunteers suggest that many exercises used during the early phase of rehabilitation to regain active elevation do not exceed 20% MVC. Progression from passive to active-assisted can potentially be performed without significantly increasing muscular activation levels exercises. Upright active exercises demonstrated a consistent and often a statistically significant increase in muscular activities supporting that these exercises should be prescribed later in a rehabilitation program.