A system for the analysis of posture and stance in quadrupeds

This paper describes a system for the quantitative analysis of posture and stance in the freely standing quadruped. The focal point of the system is a moving force platform operated by hydraulic servos under computer control. Cats are trained to stand on a support consisting of 4 force plates. Stance is perturbed by the controlled movement of the platform and the evoked postural responses are quantified in terms of the ground reaction forces, the activity of selected muscles, and the movements of the body segments. New developments that are described include: (1) the moving platform, (2) a miniature, triaxial force plate for detecting ground reaction forces under each paw, and (3) a new video camera capable of freezing rapid movements.