Meeting Abstract

79.1  Friday, Jan. 6  Slip Perturbation Recovery in the Frilled Dragon, a Dynamically Stable Bipedal Runner MARA, K.R.*; HSIEH, S.T.; Temple University; Temple University

In nature animals often encounter unsteady or unpredictable surfaces and must traverse them while maintaining dynamic stability. Yet, most previous locomotor studies have focused on steady state, non-perturbed, locomotion. As a result, the effects of an unexpected perturbation on center of mass (COM) dynamics and subsequent recovery kinematics remain relatively poorly understood. The goal of this study was to describe locomotor kinematics during unperturbed bipedal locomotion, slip perturbation, and ensuing slip recovery in the frilled dragon (Chlamydosaurus kingii), a dynamically stable bipedal runner. We used a 3D auto tracking system (Motion Analysis Corp.) to identify body and limb kinematics in frilled dragons as they encountered, and recovered from, an unexpected slip perturbation. Our preliminary data indicate that in response to an unexpected slip perturbation frilled dragons modify their locomotor kinematics to minimize perturbations to the COM and maintain dynamic stability. During the stride in which the slip perturbation occurs, the unperturbed leg exhibits a shorter swing time, thereby decreasing the overall stride duration and increasing stride frequency. Consequently, the stride frequency is increased during the slip perturbation but returns to normal after one recovery stride. Furthermore, duty factor for the foot encountering the slip perturbation is lower (0.34 ± 0.02 SE) than the non-slip foot (0.46 ± 0.02) with both feet returning to expected (non-slip) duty factors (0.38 ± 0.02) within 1 recovery stride. Finally, we found that lower limb kinematics were remarkably similar between slip perturbation trials and steady state non-slip trials. Lower limb kinematics and COM dynamics during slip perturbation and slip recovery will also be discussed.