Meeting Abstract
P1.158 Monday, Jan. 4 Effects of increased rotational inertia on the mechanics of human cutting turns BROWN, Brian*; JINDRICH, Devin L; Arizona State University; Arizona State University brian.brown@asu.edu
Locomotion in the environment is seldom steady-state. Animals and humans must constantly maneuver to change direction and negotiate obstacles. Maneuvering performance can determine predation risk for animals injury risk for humans. However, the mechanics and motor control of maneuverability are poorly understood. Comparative studies have suggested that common mechanical constraints and control strategies may be used by a diversity of runners. A simple algebraic model can successfully relate the ground-reaction forces used by bipeds (ostriches and humans) and hexapods (cockroaches) during running turns to a limited set of morphological and behavioral parameters. However, the active responses of to perturbations have not been determined. We sought to assess the mechanical and behavioral consequences of perturbations to two morphological parameters: mass (M) and rotational inertia (I). We studied humans during moderate-speed running. We constructed a rigid backpack frame with rigid poles attached at the waist, extending fore and aft. The apparatus weighs 5.7 kg. The pack is tightly fitting and adjustable to each participant. By adding mass to different locations fore and aft of the center of mass (COM), M and I could be independently changed. Changes in M of 1%-4% can increase I about the vertical axis by 1-4 times. Kinematics were collected using a VICON® 3-D motion tracking system, and ground-reaction forces measured using two force platforms (Bertec) covered by rubber mats to obscure their location. Subjects ran at 3 m/s and executed sidestep cuts with their right leg. Preliminary results suggest that although increasing I may decrease braking forces somewhat, even the highest (4%) increases were not associated with acceleratory forces, suggesting active changes to other behavioral parameters in addition to ground-reaction forces.
