The belly-press test for the physical examination of the subscapularis muscle: electromyographic validation and comparison to the lift-off test.
The purpose of this study was to determine the validity of the belly-press test as a clinical test for the subscapularis muscle with the use of electromyography (EMG). In addition, the belly-press and lift-off tests were compared to determine whether the two physical examination techniques are equivalent in their evaluation of the upper and lower portions of the subscapularis muscle. EMG data of 7 muscles (upper subscapularis, lower subscapularis, infraspinatus, latissimus dorsi, teres major, pectoralis major, and supraspinatus) were studied in 16 healthy volunteers. Average EMG amplitudes were contrasted within and between tests. Both the belly-press and lift-off tests activated the upper and lower portions of the subscapularis muscle greater than all other muscles, indicating that both tests are valid and specific for evaluation of the subscapularis muscle (P <.05). The belly-press test was found to activate the upper subscapularis muscle significantly more than the lift-off test (P <.05), whereas the lift-off test was found to pose a significantly greater challenge to the lower subscapularis muscle than the belly-press test (P <.05). These findings may improve the clinical testing and assessment of the subscapularis muscle.