Meeting Abstract

P2.195  Thursday, Jan. 5  Limb swing dynamics of wild turkeys during normal and perturbed swings. CLIFTON, GT*; HONG, C; GEYER, H; BIEWENER, AA; Harvard ; Harvard; Carnegie-Mellon; Harvard

Existing research on muscle control of terrestrial locomotion focuses on stance, during which the limb supports the body and propels the center of mass forward. Limb swing has often been assumed to occur passively through inertial pendular motion. Past work suggests that this is unlikely, yet the limb dynamics during normal and perturbed swings is poorly understood. To characterize the swing phase we recorded limb kinematics using high-speed videography of wild turkeys (M. gallopavo) walking and running on a treadmill. Perturbation trials were taken using rectangular obstacles attached to the belt of the treadmill as swing-phase perturbations. We limited analysis of perturbed trials to steps directly upon the obstacle. Data for three turkeys showed consistent joint angle and dynamics patterns across a range of speeds (0.42 – 5.42 m/s). The hip and knee torques demonstrate almost exact inverse coupling. The ankle torque exhibits a smaller coupling with the knee, which increases during the latter portion of swing phase. This suggests that biarticular tissues, muscle or tendon, strongly contribute to the limb’s swing dynamics in normal walking and running. Joint work patterns also reflect this coupling. Hip flexion work is paired with knee extension and ankle flexion. In contrast, the tarsometatarsophalangeal (TMP) joint works like a simple spring, extending quickly then flexing during swing. In perturbed swings, all three turkeys maintained strong coupling of the hip and knee torques, although the patterns significantly changed. Thus, control mechanisms for obstacle negotiation may continue to rely on biarticular structures across the hip and knee joints. These results contribute to our understanding of neuromuscular control of limb swing and perturbation recovery in bipeds.