Fig. 1. Anuran model morphology. (A) Dorsal view showing an ellipsoid body and cylindrical leg segments connected to two thin plate feet. Foot velocity components are also shown: cranio-caudal translational velocity (v_t), medio-lateral translational velocity (v_l) and rotational velocity (v_r). The foot angle (_f) is defined with respect to the body midline, and v_COM denotes the forward swimming velocity of the body (COM, center of mass). Joint angles at the hip (_h), knee (_k) and ankle (_a) are indicated with shaded discs. (B) Posterior view showing the shape and dimensions of the feet. The coordinate system used for added mass calculations is shown by arrows for aft-directed translation (x), lateral translation (y) and a rotational axis (z) about the ankle. A separate coordinate system is used for the motion of the body. Velocity in the direction of the arrows is defined as positive in their respective coordinate systems. All dimensions shown correspond to measurements taken from frog 1. Note that all limb movements are constrained to occur in the frontal (x–y) plane. a–c, dimensions of the foot.