Impact of visual rotations on heading direction and center of mass control during steady state gait.

Abstract

Visual information is essential to navigate the environment and maintain postural stability during gait. Visual field rotations alter the perceived heading direction and center of mass (CoM) trajectory. This interaction, referred to as visual coupling, is poorly characterized during steady-state gait. Moreover, it is unclear how visual field rotations affect CoM control relative to the continuously changing base of support (BoS). This study aimed to characterize the role of visual information in heading and mediolateral (ML) balance control during unperturbed, steady-state gait. Sixteen healthy participants walked on an instrumented treadmill, naïve to sinusoidal low-frequency (0.1 Hz) rotations of the virtual environment. Rotations had a 1) high (CMH) or 2) low amplitude (CML), or were 3) periodical left-right manipulations (PM) with 10 second intervals. Coupling between CoM trajectory and visual manipulations was in-phase and showed strong cross-correlations on group level (CML: 0.88, CMH: 0.91 and PM: 0.95) and moderate to strong on individual level (CML: 0.52 ± 0.15, CMH: 0.56 ± 0.17 and PM: 0.80 ± 0.07). Higher manipulation amplitudes induced stronger CoM trajectory deviations. The margin of stability (MoSML), characterizing ML balance control, decreased towards the deviation direction and increased at the opposite side. Furthermore, a pelvis and feet reorientation towards the manipulation direction was observed. We concluded that visual information is continuously used to determine and adjust heading direction during steady-state gait. To facilitate these adjustments, the body was reorientated and the CoM-ML shifted closer to the lateral BoS boundary towards the adjusted heading direction, while preserving CoM excursion.