Meeting Abstract

115.3  Monday, Jan. 7  Compensations for increased rotational inertia during human cutting turns JINDRICH, DL*; QIAO, M; California State University, San Marcos; Arizona State University djindrich@csusm.edu

Locomotion in a complex environment is seldom steady-state, but the mechanisms used by animals to power and control unsteady locomotion (stability and maneuverability) are not well understood. We used a morphological perturbation (increased rotational inertia) to determine the compensations used to perform sidestep cutting turns during running. Previous studies have argued that because humans have low yaw rotational inertia relative to body mass, braking forces are used to prevent body over-rotation during turns. We tested the hypotheses that increasing body rotational inertia would allow for decreased braking forces during stance. We recorded ground reaction force and body kinematics from seven participants performing 45 degree sidestep cutting turns and straight running at 5 levels of body rotational inertia, with increases up to 4-fold. Braking forces remained consistent at different rotational inertias, facilitated by anticipatory changes to horizontal plane body rotational speed. Moreover, increasing inertia revealed that the opposing effects of several turning parameters (i.e. initial rotation and rotation due to medio-lateral forces) result in a system that is robust to changes in rotational inertia. These results suggest that in submaximal effort turning, legged systems are robust to changes in morphological parameters, and that compensations can involve relatively minor adjustments between steps to change stance initial conditions.