## 2 Objectives and Hypotheses  
The first aim of this study is to determine whether concurrent headshake and weight shift training using virtual reality (Concurrent VR HS-WST) can change vestibular-ocular and -motor responses in healthy young adults. It is hypothesized that VOR gain, eye movement variability, and the amplitude of the electromyography (EMG) signal will significantly decrease following the training intervention. Similarly, the center of pressure (COP) sway velocity during ramp perturbation will significantly increase (indicating improved postural flexibility), while COP sway area, anteroposterior standard deviation (AP Std), and mediolateral standard deviation (ML Std) sways will decrease following the training intervention. Moreover, the time between the COP maximum peak to the minimum peak of the trajectory during ramp perturbation will significantly decrease (indicating faster automatic postural response).  
The second aim is to determine whether Concurrent VR HS-WST can reweight the sensory systems of postural control processing in healthy young adults. It is hypothesized that the Modified Clinical Test of Sensory Interaction on Balance (mCTSIB) equilibria and composite scores will significantly improve following the training intervention. Sensory weighting will change significantly, as indicated by changes in visual, somatosensory, and vestibular dependence. Postural stability will improve (i.e., COP sway area, velocity standard deviation [Vel Std], AP Std, and ML Std sways will decrease, while COP multiscale entropy velocity will increase).  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Study** & **Purpose and Contribution of the Study** \\ \hline [PERSON] \& [PERSON] [15] & Assessment of sensory reweighting of postural control processing after combined vestibular activation with voluntary weight shift training. Improvements in somatosensory reweighting, center of pressure (COP) multiscale entropy sway velocity, and COP mediolateral standard deviation sway. \\ \hline [PERSON] et al. [16] & Assessment of vestibular and motor responses following concurrent vestibular and balance training. Significant changes in VOR gain, eye fixation, refined muscle activation, and postural flexibility. \\ \hline [PERSON] et al. [17] & Evaluation of virtual reality-based vestibular rehabilitation in unilateral vestibular dysfunction. Significantly higher VOR gain, improved posturography scores, and better reduction in dizziness scores in the virtual reality-based vestibular rehabilitation group compared to the traditional vestibular rehabilitation group. \\ \hline [PERSON] [18] & A short review of the efficacy of VR to enhance vestibular rehabilitation. The use of VR devices in vestibular rehabilitation motivates participants to enjoy the training, increase their concentration, and decreases the dropout rate, as well as helps individuals with visual vertigo. \\ \hline [PERSON] \& [PERSON] [19] & A review of vestibular rehabilitation (VeR) for BVP (Bilateral vestibulopathy) and VeR using VR to increase vestibulocular reflex gain and decrease dizziness. \\ \hline [PERSON] et al. [20] & A systematic review to investigate the effectiveness of VR-based vestibular rehabilitation. The addition of VR to vestibular rehabilitation showed equal benefits in individuals with vestibular dysfunction and may be more beneficial than traditional rehabilitation alone. \\ \hline [PERSON] et al. [21] & A systematic review of the effectiveness of VR-based vestibular rehabilitation. Evidence suggests that there are clinical benefits in VR-based vestibular rehabilitation. \\ \hline [PERSON] et al. [22] & A meta-analysis to assess the advantages of VR-based vestibular rehabilitation over traditional vestibular rehabilitation. VR-based vestibular rehabilitation is suggested to demonstrate additional clinical benefits to vestibular dysfunction, especially to those with peripheral disorders. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Review of the related literature.