Visuomotor adaptation of voluntary step initiation in older adults

Abstract

It has been suggested that feedforward planning of gait and posture is diminished in older adults. Motor adaptation is one mechanism by which feedforward commands can be updated or fine-tuned. Thus, if feedforward mechanisms are diminished in older adults, motor adaptation is also likely to be limited. The purpose of the study was to compare the ability of healthy older versus young adults in generating a voluntary stepping motor adaptation in response to a novel visual sensory perturbation. We recorded stepping movements from 18 healthy older and 18 young adults during baseline and adaptation stepping blocks. During baseline, the stepping target remained stationary; in adaptation, a visual perturbation was introduced by shifting the target laterally during mid-step. We compared adaptation between groups, measured by improvements in endpoint accuracy and movement duration. Older adults adapted stepping accuracy similarly to young adults (accuracy improvement: 29.7 ± 27.6% vs. 37.3 ± 22.9%, older vs. young group respectively, p = 0.375), but showed significant slowness during movement. Thus older adults were able to achieve accuracy levels nearly equivalent to younger adults, but only at the expense of movement speed, at least during the early adaptation period (movement duration: 1143.7 ± 170.6 ms vs. 956.0 ± 74.6 ms, p < 0.001). With practice, however, they were able to reduce movement times and gain speed and accuracy to levels similar to young adults. These findings suggest older adults may retain the ability for stepping adaptations to environmental changes or novel demands, given sufficient practice.

Predictive and Reactive Locomotor Adaptability in Healthy Elderly: A Systematic Review and Meta-Analysis

“…F Healthy Design: Disturbed treadmill walking Perturbation: Different speeds of the belts (100 % and 50 % of fastest comfortable speed) Protocol: Tied-belt (baseline), split-belt for 10 min (early: mean of first 5 steps; mid: mean of 5 steps after 5 min; late: mean of last 5 steps), wash-out, split-belt for 2 min (readapt: mean of first 5 steps) and again tied-belt (post-tied: mean of 5 steps) Parameter: Step length, stride length and stance time asymmetry Intra-limb (stride length and stance time asymmetry) and inter-limb (step length asymmetry) LA as well as predictive (baseline vs. post-tied) and reactive (early vs. readapt) adaptive changes Similar predictive and reactive adaptive responses of young and older adults to the sequence of tied- and split-belt walking Sakai et al [ 113 ] O: n = 45 (71 ± 4 years), 26 F Healthy Design: Disturbed treadmill walking (2 km/h) Perturbation: Slip (i.e., decelerating right belt for 500 ms at TD of the heel) Protocol: 20 perturbations repeatedly in a 5-min walk Parameter: Sway, muscle activity (EMG) of lower limbs and trunk, stride time Magnitude of LA as difference between average of 10 early (first half) and 10 late (second half) subsequent perturbations steps Older adults showed reduced sway (i.e., more stable) in the second half of 20 disturbed steps (LA). While muscle EMG latencies were unchanged, two muscles of the limb indicated reduced EMG magnitude in the second half Tseng et al [ 114 ] O: n = 18 (72 ± 4 years), 12 F Y: n = 36 (26 ± 4 years), 13 F Healthy Design: Disturbed stepping movements (‘step fast and accurate’) Perturbation: Left or right shift of visual step target during volitional step initiation Protocol: 20 baseline steps followed by a block of 30 adaptation trials (target shift) Parameter: Step accuracy (foot position), duration (total, response time, weight transfer, stepping execution) Magnitude of LA as difference of early (first 3 of 30 steps) and late adaptation trials (last 3 of 30 steps) Older adults adapted stepping accuracy almost equivalent to young adults but showed slowness during the stepping movement in the early adaptation phase. With practice, older adults reduced their movement times to levels similar to young adults Yang and Pai [ 61 ] O: n = 73 (73 ± 5 years), 46 F ([ 61 , 72 – 74 ] same pool) Design, perturbation and protocol see Bhatt et al [ 72 ] (same as in [ 61 , ...…”

Neural Control of Human Locomotor Adaptation: Lessons about Changes with Aging

“…Aging studies on feedback adaptation during perturbed visually guided stepping have shown that older adults may have impaired reactive feedback processes (Table 2). When visual cues on the floor were laterally perturbed while participants were standing, older adults demonstrated delayed reactive adaptation compared to young adults, but the size of stepping error (i.e., spatial accuracy) was not impaired with increased age (Tseng and others 2009; Tseng and others 2010). With perturbed visual stepping targets in the anterior-posterior direction during treadmill walking, older adults demonstrated larger stepping error compared to younger adults (Mazaheri and others 2015).…”

Use of virtual reality technique for the training of motor control in the elderly

“…It has been suggested that feed-forward planning of gait and posture is diminished in older adults. Motor adaptation is one mechanism by which feed-forward commands can be updated or fine-tuned [40]. The ability to make timely, appropriately directed steps underpins our ability to maintain our balance and move unaided through our environment [41].…”