The Effects of Delayed Visual Feedback on Dynamic Postural Control.

Purpose: Vision provides essential sensory feedback to maintain upright stance yet is affected by inherent processing delays within the central nervous system. Mismatches between visual and motor responses caused by visual delays may also result in motion sickness. In the current study, virtual reality (VR)-generated visual delays were used to examine the relationships among delayed visual feedback, postural responses, and visually induced motion sickness during a dynamic balance task. Methods: Young healthy adults stood on a force plate mounted to a motorized platform that sinusoidally translated continuously in the anteroposterior (AP) direction for 60 seconds; they wore a VR head-mounted display, surface electromyography (EMG), and full-body motion capture markers. Center of pressure (CoP) was recorded through ground reaction forces using the force plate, kinematics were collected to observe whole-body responses, and surface EMG was used to record muscle activity. Questionnaires were completed after each trial to evaluate subjective measures of perceived stability and visually induced motion sickness. Results: The amplitude of kinetic, kinematic responses, and muscle activity increased with visual delay and returned to baseline levels when participants were re-exposed to the visual delay conditions. Conclusions: Strategies used to maintain postural stability under delayed feedback conditions can adapt to sensory delays, without experiencing motion sickness, even if the perceived stability is initially compromised.