The effects of cognitive demand on distributions of medial and lateral plantar loads while walking in anxiety-inducing virtual settings.

Introduction: Both fall-related anxiety and cognitive demands affect balance and gait without additional motor complexity. High elevation settings in virtual reality elicit 'stiffening of posture' (i.e. reduced sway) and gait (i.e. slower gait speeds) that may influence locomotor balance. The purpose of this exploratory analysis was to examine locomotor balance control during a dual-task (DT), extemporaneous speech, and in anxiety-inducing settings. We predicted cognitive demand and fall-related anxiety would affect mediolateral locomotor balance, indicated by the difference between medial and lateral plantar loads.

Methods: Participants were pseudorandomized into single-task (ST) or DT blocks first but always walked in low before high elevation virtual environment. Participants walked on a wooden walkway at a self-selected pace in virtual settings for one minute while wearing a head-mounted display (HTC Vive, version 2.0) and in-shoe load sensors (Loadsol Pro, novel). For the DT, participants concurrently spoke extemporaneously about a randomly assigned topic. Locomotor balance was examined using the distribution between the medial and lateral plantar loads across normalized stance. Statistical parametric mapping determined significant differences in medial and lateral plantar load distributions between walking conditions.

Results: Insoles were fitted onto participants (N = 8, five women, height = 1.7 (0.1) meters, weight = 71.8 (11.5) kilograms). The SPM two-dimensional repeated measures ANOVA found a region of difference for the main effect of height from 33 % to 35.5 % of stance (p = .033). The medial and lateral plantar load distribution was decreased representing a more medial position of the center of pressure (COP) at approximately 34 % of the stance phase walking at high VR height compared to low VR height.

Significance: Walking in anxiety-inducing settings , but not umder cognitive demand, was associated with a more medial position of the COP at 34 % of stance, suggesting a dynamic spatially-based balance response to laterally-oriented postural threats during the early stance phase of a step.