# Evaluating the Impact of Optokinetic Stimulation on Weight Balance and Muscle Strength in Healthy Individuals in Virtual Reality During Squats

## TL;DR

This study shows that torsional optokinetic stimulation during squats in virtual reality can shift weight and increase muscle activity in healthy individuals.

## Contribution

The study introduces the use of torsional optokinetic stimulation during squats to correct weight and muscle imbalances in a virtual reality setting.

## Key findings

- Torsional OKS caused a significant weight shift toward the stimulus side during squats.
- Torsional OKS increased muscle activity by 3.4% on the stimulus side during both flexion and extension phases.
- Both horizontal and torsional OKS increased center of pressure sway during squats.

## Abstract

Background

Asymmetry in lower limb muscle strength and weight-bearing imbalance, commonly observed among athletes, individuals with unilateral impairments, and stroke survivors, require targeted interventions to correct left-right imbalances. Such corrections are essential for enhancing athletic performance, minimizing injury risks in athletes, and improving gait functionality and daily activity efficiency in patients. This study explored, in healthy participants, the potential of combining squat training with optokinetic stimulation (OKS) in an immersive environment to improve left-right balance and address asymmetries in muscle activity and weight distribution.

Methodology

OKS was delivered using a random dot pattern rotating around either the longitudinal axis (horizontal OKS (HOKS)) or the frontal axis (torsional OKS (TOKS)) during squats. Weight-bearing was evaluated by analyzing the center of pressure (CoP) position and foot pressure (FP). Electromyography (EMG) activity was recorded from the following four leg muscles: the vastus lateralis, vastus medialis, semitendinosus, and biceps femoris.

Results

Both HOKS and TOKS increased the CoP sway during squats by 38.6% and 58.6%, respectively, compared to the control. However, only TOKS caused a significant weight-bearing shift toward the stimulus side. During TOKS, FP significantly increased by 10.9% on the stimulus side and decreased by 8.9% on the non-stimulus side, reinforcing the weight-bearing shift. Additionally, EMG activity was significantly elevated by 3.4% on the stimulus side during TOKS, both during the flexion and extension phases. Safety was confirmed during all measurements.

Conclusions

These findings indicate that TOKS induces a shift in weight-bearing and enhances muscle activity, highlighting its potential as a therapeutic intervention for correcting asymmetrical patterns in muscle activity and weight distribution.