One Step, Two Steps, Three Steps More Directional Vulnerability to Falls in Community-Dwelling Older People

Abstract : Falls leading to disability are common occurrences with advancing age. Stepping is a natural protective option for maintaining balance and preventing falls. There are directionally dependent challenges for protective stepping associated with falls among older individuals. The aim of this study was to determine the stepping response patterns evoked by different directions of externally applied postural disturbances in younger and older adults and in relation to falls. Seventy-five community-dwelling adults were tested: 26 younger adults and 49 older adults. Fall history of older participants was tracked prospectively for 1 year after testing. Steps were randomly evoked in 12 directions by a motorized waist-pull system. The number of recovery steps, type of stepping strategy, and first step kinematic characteristics were determined. Younger participants mainly used single recovery steps regardless of the perturbation direction. For the older groups, multiple steps occurred predominantly and were least for the forwardbackward directions and greatest for the lateral directions. Trials with three or more recovery steps were increased laterally only for the fallers. Overall, fallers initiated stepping earliest, but other stepping characteristics were similar between the groups for forwardbackward perturbations. Aging differences in stepping strategies for diagonal and lateral perturbations included numerous interlimb collisions. Adaptive changes in stepping characteristics between forward and lateral perturbations were also observed in relation to age and risk of falls. These results indicated an age-associated reduction in balance recovery effectiveness through stepping particularly for the lateral direction among older individuals at greater risk for falls.