Meeting Abstract
44.2 Wednesday, Jan. 5 Limb swing dynamics of wild turkeys as a function of speed and gait. CLIFTON, G.*; HONG, C.; GEYER, H.; BIEWENER, A. A.; Concord Field Station, Harvard U., Bedford, MA; CFS, Harvard U., Bedford, MA; Robotics Institute, Carnegie-Mellon University, Pittsburgh, PA; CFS, Harvard U., Bedford, MA glenna.clifton@gmail.com
Although it plays a major role for gait stability, comparably little is known about the limb swing dynamics of terrestrial animals during normal swings and recoveries. Terrestrial animals increase speed mainly by decreasing stance phase duration (and duty factor) to increase stride frequency, with a more uniform swing phase period. While this may suggest that limbs swing like passive pendulums, past work shows that this is unlikely the case. It is unclear, however, how the inertial dynamics of limb swing and recovery are controlled across speeds and gaits. To begin investigating swing dynamics and control, we recorded the kinematics of limb swing (QualysisTM motion capture at 240 Hz) in wild turkeys (M. gallopavo) walking and running on a treadmill. The inertial dynamics of limb motion were determined using inverse dynamics based on the recorded kinematics and segmental inertial properties. Data for two turkeys show consistent inertial dynamics across a range of walking and running speeds (0.42 – 5.42 m/s). A strong coupling of joint torques exists throughout swing for the hip and knee. The ankle torque shares in this coupling in the second half of swing, while it is coupled with that of the tarsometatarsal (TMT) joint in the first half. This suggests major contributions of biarticular structures, muscles or tendons, to swing limb dynamics in walking and running. The coupling is also reflected in the joint work patterns. Hip flexion work is coupled to knee and ankle extension work. In contrast, the TMT joint operates as a simple rotary spring, flexing during the first half and re-extending before the second half of swing. Future work will use these results to better understand and simulate the neuromuscular control of limb swing and swing recovery in animals and humans.
