Electromyographic Activities of the Rotator Cuff Muscles During Walking, Eating, and Washing.

OBJECTIVE: The aim of this study was to evaluate the activity of rotator cuff (RC) muscles during activities of daily living.

DESIGN: Motion analysis was conducted with 14 volunteers. Activation of RC (subscapularis, supraspinatus, and infraspinatus) was assessed using electromyography (EMG). Walking was performed with or without a shoulder immobilizer. Eating was conducted with or without the support of the elbow with the contralateral hand. Washing the hair was simulated while standing or leaning forward; washing the body was simulated while standing or holding the elbow; and washing the face was simulated using both hands while leaning forward.

RESULTS: During walking, RC's peak EMG activities remained below 7% maximum voluntary isometric contraction at all times, regardless of the use of immobilizers. Eating caused mild EMG activities (14%-32%), whereas eating with elbow support resulted in significantly lower EMG activities in the supraspinatus and infraspinatus. Washing the hair standing moderately activated RC (23%-57%), whereas leaning forward decreased it to 6% to 36%. Washing the body while holding the elbow decreased infraspinatus activation to 4% from 10% when standing. Washing the face with both hands and leaning forward resulted in high-peak EMG activities in the upper subscapularis (37%).

CONCLUSIONS: There was no difference in RC activity level between walking with or without immobilizers. From the point of muscle contraction, an immobilizer is not mandatory. Holding the elbow with the contralateral hand while eating or washing can help decrease the load in the supraspinatus and infraspinatus.