Meeting Abstract

S5.2-2  Sunday, Jan. 5 10:30  Compensations During Unsteady Locomotion. QIAO, M; JINDRICH, D. L.*; University of Omaha; California State University, San Marcos

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 use behavioral, morphological, and impulsive perturbations to determine the compensations used during unsteady locomotion. At the both the whole-body and joint levels, quasi-stiffness models are useful for describing adjustments to leg and joint function associated with maneuvers. However, alterations to leg and joint mechanics are often distinct for different phases of the step cycle or specific joints. For example, negotiating steps involves independent changes of leg stiffness for compression and thrust phases of stance. Moreover, the compensations used to reject impulsive lateral perturbations may be gait and step phase dependent. Unsteady locomotion also involves parameters that are not part of the simplest reduced-parameter models of locomotion (e.g. the Spring-Loaded Inverted Pendulum). Extensive coupling among translational and rotational parameters must be taken into account to stabilize locomotion or maneuver. For example, maneuvers with morphological perturbations (increased rotational inertia turns) involve changes to several aspects of movement, including initial rotation conditions and ground-reaction forces. Coupled changes to several parameters may be employed to control maneuvers on a trial-by-trial basis. Compensating for increased body inertia during turns is facilitated by the opposing effects of several mechanical and behavioral parameters. Consequently, reduced-parameter models can be useful for describing unsteady locomotion, but animals may employ coupled changes to many parameters that depend on context.