Fig. 7. Fore-aft (blue) and lateral (green) center of mass (COM) wall reaction forces, COM fore-aft and lateral instantaneous velocity for two steps (one stride) during climbing for (A) a cockroach, (B) a gecko and (C) the spring-mass model (template). Cockroaches and geckos show similar COM wall reaction forces and velocities. This pattern can be represented by the template described in Fig. 8. The fore-aft and lateral forces are in-phase and the lateral force is one-half the oscillation frequency of fore-aft force. The velocities are phase-delayed from the corresponding forces by approximately /2. Climbing velocity for the cockroach is 20 cm s^-1, the gecko 49 cm s^-1, and the template 18 cm s^-1. Broken lines indicate body weight. The stepping patterns are shown below for a normalized stride. Black bars represent stance period and white spaces the swing period.