Fig. 9.

Dependence of torque direction (ALPHA) on humeral rotation [ROT (ζ)] and upper arm azimuth (η) for each of the six muscles. Data are the same as those presented in the top plots of Figures 5and 6 (Subject C). α is the angle in theM_x/M_yplane, relative to the −M_x (ABD)-axis. Negative values of humeral rotation indicate external rotation; positive values indicate internal rotation. The diameters of the individual circles are proportional to values of upper arm azimuth, with the largest circles corresponding to the most lateral elbow locations.