Distributions of plantar loads are altered when walking in anxiety-inducing virtual settings but not under cognitive demand

Abstract

Additional cognitive load and fall-related anxiety alter balance and locomotor control, independent of motor demands. Exposing participants to virtual elevation increases perceived cost of falling, and individuals alter the distribution of medial and lateral plantar loading to maintain balance and avoid a lateral postural threat (in virtual reality). Here, we extend this prior work to examine anterior and posterior loading in response to cognitive demand and virtual elevation to induce anxiety. We predicted that the distribution of plantar loads between the medial and lateral, and anterior and posterior compartments of in-shoe load sensors would indicate within-step changes to locomotor balance control across walking conditions. Healthy participants (N=16) were pseudorandomized into single- or dual-task trial blocks first. While wearing a head-mounted virtual-reality display and in-shoe load sensors, participants walked at self-selected pace overground on a 40cm wide by 5.2 m long walkway at virtual high and low elevation during single and dual-tasks. For dual-tasking, participants walked and talked extemporaneously about a randomly selected topic. All participants wore their own footwear. The distribution of medial and lateral and anterior and posterior loads was computed across normalized stance. Statistical parametric mapping determined significant differences in plantar load distribution by walking condition. Fall-related anxiety led to a more medial load distribution during 11% to 75% of stance and more posterior distribution during heel strike from 0% to 4% of stance. There were no load distribution changes due to the extemporaneous speech dual-task. Walking at high virtual elevation, not during a dual-task, led to a medial shift in plantar load during stance, and more posterior loading during initial contact. Plantar load distributions were primarily adjusted within-steps to avoid lateral postural threats when step width was constrained by a narrow path.