VALIDATION OF THE LIFT-OFF TEST AND ANALYSIS OF SUBSCAPULARIS ACTIVITY DURING MAXIMAL INTERNAL-ROTATION

We used electromyographic analysis to determine the muscle activity of the shoulder muscles during the lift-off test and during resisted int ernal rotation, The activity in the upper and lower subscapularis musc le during a lift-off test from the region of the midlumbar spine was a pproximately 70% of maximal voluntary contraction. This level was sign ificantly higher than for all the other muscles tested (P < 0.05). The lift-off test with the hand placed in the region of the midlumbar spi ne resulted in one-third more electromyographic activity in the subsca pularis muscle than when the test was modified and performed with the hand at the buttocks region. A resisted lift-off test resulted in high er activities in all the muscles, but only a small increase in the pec toralis major muscle, The pectoralis major muscle was significantly mo re active during resisted internal rotation with the arm in front of t he body. Comparison of activity in the upper subscapularis with that i n the lower subscapularis muscle showed no significant differences dur ing any of the tests, This study documents the importance of the subsc apularis muscle during the lift-off test and suggests that other poten tial internal rotators of the humerus have a limited role in maintaini ng internal rotation when the arm is placed behind the back.