KINESIOLOGY OF THE EMPTY CAN TEST

The ''empty can test'' has been described to isolate supraspinatus mus cle activity from the activity of other rotator cuff muscles. The shou lder is positioned in 90 degrees of abduction, with full internal rota tion, and 30 degrees of forward flexion and maintained against resista nce. The purpose of this study was to determine if the supraspinatus m uscle is isolated by the empty can test. Ten normal male subjects were studied (age 25-43/mean 32) with fine-wire electromyography recording from their nondominant arm middle deltoid, supraspinatus, infraspinat us, and teres minor. During the maneuver electromyogram activity was s een not only in the supraspinatus, but also in the infraspinatus and t he middle head of the deltoid. Teres minor was inactive throughout the test; however, this is interesting because the teres minor and infras pinatus have previously been described as a functional unit. Our study found that the empty can test does not allow selective activation of the supraspinatus muscle.