Control of rapid limb movements for balance recovery: age-related changes and implications for fall prevention

Abstract

BACKGROUND: balancing reactions that involve rapid stepping or reaching movements are critical for preventing falls. These compensatory reactions are much more rapid than volitional limb movements and can be very effective in decelerating the centre-of-mass motion induced by sudden unpredictable balance perturbation; however, age-related deterioration in the neural, sensory and/or musculoskeletal systems may impede the ability to execute these reactions effectively. OBJECTIVE: this paper summarises recent research regarding age-related changes in compensatory stepping and reaching reactions and the practical implications of these findings for fall prevention programmes. RESULTS: even healthy older adults experience pronounced difficulties. For stepping reactions, the main problems pertain to control of lateral stability--arresting the lateral body motion that occurs during forward and backward steps, and controlling lateral foot movement so as to avoid collision with the stance limb during lateral steps. Older adults appear to be more reliant on arm reactions than young adults but are less able to execute reach-to-grasp reactions rapidly. CONCLUSIONS: it is important for clinicians to assess compensatory stepping and reaching, in order to identify individuals who are at risk of falling and to pinpoint specific control problems to target for balance or strength training or other intervention. More effective use of stepping and reaching reactions can be promoted through improved design and appropriate use of sensory aids, mobility aids, footwear, handrails and grab-bars. It is particularly important to address the problems associated with the control of lateral stability because it is the lateral falls that are most likely to result in hip fracture.