Figure 2.

Simulations were started with the trailing limb in an upright configuration and the forward limb oriented at the impact angle. The double support phase started when the leading limb contacted the ground, and then continued until the trailing limb length reached its undeflected length. The second single support phase continued until the limb reached an upright configuration, signaling the end of the half-gait cycle. We searched for limit cycle solutions in which the limb length, forward velocity and vertical velocity at the end of the half-gait cycle replicated the initial conditions.