Fig. 3. Maximum force output by Group 2 motors as a function of their mass. The least squares fit (solid line) is: F_max=55 M^0.999. The dashed line is the scaling fit for Group 1 motors for which F_max scales as M^0.67 (Fig. 2). Inset: the frequency distribution of mass specific force output for all of the Group 2 motors on the main plot. Maximum force output (N) and motor mass (kg).