Meeting Abstract

74.3  Tuesday, Jan. 6  Ground Reaction Force and Center of Mass Dynamics of Goats and Dogs during Trotting and Galloping. BIEWENER, A A*; ROS, I; LEE, D V; ANTONNEN, J; HIGGINS, T; Harvard University; Harvard University; UNLV; Harvard University; Harvard University abiewener@oeb.harvard.edu

How does the center of pressure (CoP) resulting from distributed limb ground reaction forces (GRF) track the center of mass (CoM) of an animal as it moves using different gaits? What are the patterns of pitch, roll and yaw moments that result from mismatches in CoP and GRF-CoM tracking? We recorded GRF, CoP and limb and body kinematics to estimate CoM location of goats and dogs as they trotted and galloped steadily across four force platforms, providing a full stride cycle map of CoP/GRF-CoM tracking and CoM moments. We hypothesized that pitch moments would be greatest for galloping due to fore-hind timing asymmetry and that roll moments would be greatest due to contralateral fore-hind contact during trotting. We found that pitch moments were greatest in both species during trotting and galloping. However, supporting our hypothesis, pitch was 2-3x greater during galloping. Dogs galloped with larger size-normalized CoM pitch moments compared with goats. CoM roll moments were 33-50% of pitch moments and yaw moments were least (15-22% of pitch). Head-up and head-down pitch was associated with fore vs hind timing of deceleration and acceleration in the direction of travel. The timing and distribution of limb GRFs during trotting and galloping in dogs and goats enables the CoP-GRF to track CoM closely, keeping CoM moments low. These studies are applied to developing more stable legged robots (supported by DARPA Biodynotics).