Effect of visual task complexity and surface instability on perturbed balance performance among healthy older adults

Purpose : Balance control is vital for safe ambulation among older adults, especially under challenging environments like dual task paradigm and unstable surfaces. Our study aimed to assess older adults’ perturbed balance in simulated real-life scenarios during visual searching and negotiating unstable surfaces. We hypothesized that experimental conditions with more challenging visual tasks and unstable surfaces would result in a decline in postural stability and longer latency among older adults.

Methods : Eighteen participants (age: 65.8±4.0 years; F/M: 15/3) without any systemic or eye diseases were recruited. All participants were instructed to stand on a perturbed force-plate on their bare-feet and complete balance assessments using Bertec Balance Advantage™ system for the following conditions: 1) standing surface (firm/ foam surface) and 2) visual task (fixating on a stationary target/ visual searching [1 target/ 3 targets]). All measurements were repeated 3 times. Reactive balance control in terms of latency reacting to perturbation (randomly moved forward and backward) and root mean square (RMS) sway of Center of Pressure (CoP) for dominant leg in anterior-posterior (AP) and medial-lateral (ML) directions were measured. Independent t-test and one-way analysis of variance (one-way ANOVA) were used to analyze the data.

Results : Contrary to our hypothesis, the effect of visual task showed non-significant influence on latency and RMS sway of the participants (F0.10). Latency for the conditions with foam surface was not significantly different from firm surface (p>0.10). Instead, the RMS sway on the foam surface in ML direction was significantly lower than firm surface (p3.682, p
Conclusions : Opposing to our hypothesis, the effect of visual task and standing surface on latency and RMS sway were weak. Surprisingly, the RMS sway on the foam surface was significantly less than firm surface. The results may be explained by posture priority. Older adults will take posture as the priority, mainly for safety reasons. They may sacrifice their attention on the visual task. Alertness may also alter the performance, therefore standing on foam may create less sway.