Age-related differences in visual sampling requirements during adaptive locomotion.

This study investigates if there are age- and falls-risk related differences in the length of time individuals need following fixation of a stepping target in order to step accurately onto it. This aim was achieved by manipulating the timing and location of stepping target presentation and comparing the effects on stepping performance between young adults, older adults characterised as having a low risk of falling and older adults characterised as having increased risk of falling (N = 10 in each group). Eye and lower limb kinematics were recorded using an eye tracker interfaced with a 3D motion analysis system. Temporal and spatial characteristics of eye and stepping movements were analysed and compared between groups and conditions in which participants had either <1, 2 or 3 s, following target fixation, in order to view and respond to target presentations. Comparisons were made between steps to centrally or laterally positioned targets (125% of individual participant's normal step width). The results showed that high-risk older adults required significantly more time than low-risk older and younger adults in order to plan and execute medio-lateral stepping adjustments. A reduced ability to make rapid sideways stepping adjustments to avoid obstacles or step on safe areas may contribute towards trips and falls in these individuals. Possible neural mechanisms underlying this group-related decline in performance are discussed.