Balance maintenance in normal seated reach.

Abstract

Seated reach capability is limited by the strength, range of motion, and balance capabilities of the individual. In forward reaches people are able to maintain balance by generating forces and torques at their hips, supporting themselves over their legs. In contrast, lateral reaches, particularly those in which torso motion is required, are frequently limited by balance. A model-based study and two experiments involving human participants investigated the effect of task characteristics (motion duration, torso recruitment, and hand load) on the differences in static and dynamic analyses and the magnitude of the center of pressure excursion. The results indicate that static, terminal posture analysis is sufficient for evaluation of most seated tasks. An additional experiment used center of pressure excursion measurement to quantify the balance-maintenance capability of thirty-eight adults ranging in age from 21 to 74 years. While the excursion capability decreased with age when a handle was not used, the use of a handle by the contralateral hand allowed older participants to produce lateral excursions similar to those of the younger participants. Three examples of how the results of this dissertation can be applied are presented. The first demonstrates how motion and postural prediction can be affected by integration of balance considerations. In the second, balance prediction and the capability estimates are used in the design of a vehicle environment. The third is an evaluation of the forward-reaching motions and strategies of people with spinal cord injury.