60.4 Friday, Jan. 6 Perturbed bipedal running: How do touch down conditions affect stance dynamics? BLUM, Y*; BIRN-JEFFERY, A; DALEY, MA; Royal Veterinary College; Royal Veterinary College; Royal Veterinary College email@example.com
Our goal is to identify control strategies used by birds to achieve stable and robust locomotion in uneven terrain. We want to investigate how touch down conditions, which are determined by swing leg control strategies, influence stance dynamics during both steady state running and in the presence of ground height disturbances (i.e. a step down). Avian running trials were conducted on a runway, and dynamics and kinematics of five birds (guinea fowl, Numida meleagris) were recorded. We had three experimental setups, consisting of a flat pathway, a ramp with a 4 cm drop and a ramp with a 6 cm drop. The results suggest that swing leg control, namely the time-dependent adjustment of leg angle and leg length in anticipation of ground contact, affects the initial conditions of the following stance phase, and therefore, controls the stance phase as well. Especially the horizontal impulse (i.e. speeding up or slowing down), and both the net center of mass work and the net leg work (i.e. energy production or absorption) seem to be strongly related to center of mass velocity, leg angle and leg length at the instant of touch down. While the flight phase might be controlled by a mainly feed-forward and time-dependant swing leg strategy with a triggered starting point, our results suggest that during stance phase the system’s energy is regulated depending on the resulting leg conditions at the instant of touch down. Such a combination of control strategies, namely a “blind” flight control with a stance control that relies on its initial conditions, could work without feedback and might explain why running birds such as guinea fowl are such remarkable obstacle negotiators.