# Correlations between SSQ Scores and ECG Data during Virtual Reality Walking by Display Type
## 4 Discussion
(2019) conducted experiments with 15 participants wearing HMDs and performing driving simulation tasks for 15 min [24]. Subsequently, they conducted SSQ surveys in which the nausea score was negatively correlated with the LF/HF ratio; however, there was no statistically significant correlation with the RMSSD. In the present study, the LF/HF ratio increased to a greater extent in the motion-sickness group than in the non-motion-sickness group. Within the motion-sickness group, the difference was greater during HMD-assisted walking than during screen-assisted walking. Psychological stress due to motion sickness is significantly correlated with an increase in the LF/HF ratio [25]. LF power is related to sympathetic activity, and HF power is related to parasympathetic activity [26]. This indicates that the cybersickness induced in the participants increased the LF power and decreased the HF power. The increase in the LF power indicates that the sympathetic nervous system is dominant, which can be considered a bodily reaction to external stimuli. This study aimed to find reliable data for determining the variable that can predict the presence of motion sickness among several variables measured on an ECG. The RMSSD had a high negative correlation with the SSQ scores; that is, the RMSSD scores decreased as the SSQ scores increased. It is possible that the RMSSD data can be used as a reliable variable that acts as an objective indicator to differentiate the motion-sickness group from the no-motion-sickness group during walking. RMSSD is one of the main variables used to analyze the short-term components of HRV. This variable represents the short-term heartbeat variability factors and is an indicator of the controlling capacity of the parasympathetic nerves. The reduction in RMSSD with an increase in the degree of motion sickness during walking in a virtual environment represents an inappropriate response by the autonomic nervous system function and appears to influence the cardiovascular system response. Previous studies have measured motion sickness-related biosignals after constraining body movements. Hence, these studies cannot be compared with the present study, which measured motion sickness-related biosignals during walking. However, this study can be considered important fundamental research on rehabilitation incorporating virtual environments because it identified the HRV variables that can determine the presence of motion sickness when walking in VR. For example, if a patient's RMSSD value changes abruptly, the intensity of rehabilitation activities can be automatically reduced to allow the patient to participate more comfortably in the rehabilitation process. Additionally, monitoring RMSSD can detect early signs of cybersickness in the VR environment. By promptly responding when symptoms of motion sickness begin to appear, i.e., by adjusting or pausing VR activities, it is possible to minimize patient discomfort and enhance the efficiency of rehabilitation. In the future, we plan to conduct experiments according to age and patient groups requiring rehabilitation to identify the variables that can determine the presence of motion sickness when walking in VR. In addition, we aim to classify the SSQ scores, which measure the degree of motion sickness, by item to identify the symptoms that appear most prominently during VR walking and apply this to the motion sickness evaluations. We also plan to examine the changes in walking pattern that occur during VR walking by group and age and analyze the correlation between the degree of motion sickness and changes in the walking pattern.