Effect of Optokinetic Stimulation in The Virtual Reality Environment on WeightBearing Shift During Gait Movement in Healthy Subjects

Objective: This study aimed to determine whether optokinetic stimulation (OKS) in the virtual reality (VR) environment via a head - mounted display (HMD) could significantly shift weight bearing (shift of the center of pressure (CoP) position) during gait movement in healthy subjects. Patients with hemi - plegia after stroke exhibit postural instability with weight-bearing shift to the non - paretic side. This adversely affects activities of daily living, and increases the risk of falls during gait movement.Increasing the CoP on the paretic direction, and correcting the asymmetry are considered important for addressing the problems. Methods: The present study investigated the effect of OKS in a VR environment on posture balance, and assessed whether the stimulation could induce a stable shift of CoP during gait movement as well as during static standing. CoP during static standing, and the foot pressure during gait were measured to evaluate the weight-bearing balance. For OKS, a pattern of random dots was presented and was continuously moved in horizontal (HOKS) and torsional (TOKS) directions through an HMD. Results: Based on the overall results of CoP sway parameters in response to various OKS velocities in the balance test, OKS velocity of 40°/s was adopted for gait test. Both HOKS and TOKS induced a lateral deviation of the walking trajectory, a significant increase in stance period, and foot sole pressure on the stimulation side, which indicated lateral weight-bearing shift to the direction of OKS. Conclusion: The results indicate that OKS through HMD-VR can induce significant weight-bearing shift during gait movement as well as during static standing, suggesting that the approach can be applied to gait exercise training for the patients with hemiplegia as an effective tool with extensibilities.