Fig. 10. Comparison of the joint kinematics of model 3 (red lines), model 4 (blue lines) and experimental frogs (black line represents data from one frog). The forward dynamics of models 3 and 4 were driven with the joint torque pattern estimated from the kinematics of experimental frogs. The hindlimb joint angles of both models closely corresponded to the experimental data for the first 70ms of each simulation run. After 60-70ms, the metatarsal joint (Meta) of experimental frogs begins to extend (lower right panel). Model 3 did not capture this reversal of tarsometatarsal joint motion because the metatarsal—phalangeal segment was fixed to the ground. Model 4, which allowed passive rotation of the metatarsal segment above the ground (i.e. no active torques were applied about the tarsometatarsal joint), did capture this kinematic effect. ab—add, abduction—adduction; Ext, external.