Evidence for age-related decline in visuomotor function and reactive stepping adjustments

Abstract

This study investigated age-related and fall-risk-related differences in the ability to make visually guided reactive stepping adjustments during locomotion. Participants were asked to walk towards and step accurately onto a visual target which, during the step towards it, moved to an unpredictable location at an unpredictable time. We measured lower limb kinematics and eye movement characteristics of young adults and two groups of older adults deemed to be either at a low- or high-risk of falling. High-risk older adults produced significant deviations in foot trajectory with latencies of ∼300 ms, compared to 280 ms in low-risk older adults and ∼200 ms in young adults. Furthermore, high-risk older adults were unable to generate adjustments with the same magnitude and consistency as low-risk older adults and young adults. Saccadic reaction latencies also were doubled in high-risk older adults compared to young. Analysis of covariance showed that the significant between group differences in final foot placement error could be accounted for by differences in saccadic response times. We propose that age-related delays in visuomotor processing times may disrupt the timing and magnitude of stepping adjustments, possibly contributing to an increased likelihood of falls.