Effect of handrail height and age on the timing and speed of reach-to-grasp balance reactions during slope descent.

ABSTRACT

We investigated the effect of handrail height on the timing and speed of reach-to-grasp balance reactions during slope descent, in fourteen younger and thirteen older adults. Participants walked along an 8° slope mounted to a robotic platform. Platform perturbations evoked reach-to-grasp reactions. Handrail height did not significantly affect handrail contact time (i.e., time from perturbation onset to handrail contact) or movement time (i.e., time from EMG latency to handrail contact). Participants appeared to compensate for the increased hand-handrail distance with higher rails via increased peak upward hand speed, and decreased vertical handrail overshoot. Aging was associated with slower EMG latency, reduced hand acceleration time, and increased hand deceleration time. Our findings suggest that participants were not disadvantaged by higher handrails from reach-to-grasp timing or speed perspectives, and that other metrics (e.g., center-of-mass control after grasping) may be more important when evaluating handrail designs for balance recovery.