The purpose of this study was to determine the torque produced by the
supraspinatus muscle within the functional motion planes of forward flexion
and elevation in the plane of the scapula. An isokinetic dynamometer was
used to measure the reduction in torque produced by isolated paralysis of
the suprascapular and axillary nerves in ten normal volunteers. A
calculation of the potential torque of the supraspinatus and deltoid
muscles was obtained from the product of the moment arm, cross-sectional
area, and integrated electromyographic signal. The results of both the
dynamometer measurement and the calculation of torque supported our
conclusion that the supraspinatus and deltoid muscles are equally
responsible for producing torque about the shoulder joint in the functional
planes of motion.