## 1 Introduction  
As the population ages, falls and injuries in the elderly are a major concern leading to decreased quality of life and thus the inability to care for oneself. According to the Center for Disease Control (CDC), nearly 36 million older adults fall each year [1]. Nearly 3 million older adults were treated in emergency room departments for a fall-related injury [2, 3]. Falls are the leading cause of fatal and nonfatal injuries among persons aged over 65 years old [1]. Aging has proven to be correlated with an increase in the severity and the number of injuries [4]. Several risk factors have been identified that may lead to falls in the elderly. Postural instability when one's base of support has been reduced was identified as a major intrinsic risk factor for the older population [5]. Falls have been linked to a reduction in static balance measured by postural sway during various foot placements [6, 7]. Additionally, some studies have reported lack of exercise and increased fall risk for older adults [8, 9]. There have been several traditional programs (such as resistance training and balance exercises) aimed to increase mobility, posture, and balance to reduce falls in the elderly [8, 9, 10, 11]. Group and home-based exercise programs with various tasks significantly reduced the risk of falls of those at both high and low risk [5, 6, 8, 9, 12]. These methods have proven somewhat effective in that there are still issues with compliance and realistic testing environments. Virtual reality (VR) training has the capability to provide a safe environment that can create scenarios that simulate real life. Mobility and balance practice using a VR headset may provide an avenue for accessible, effective home-based balance training. Additionally, other external settings, such as rehabilitation facilities, senior centers, or nursing homesmay also benefit. More recently, researchers have begun to use VR headsets to explore their impact on balance and falls in elderly adults [13; 14; 15; 16; 17]. Several studies have displayed that VR training increases the possibilities of motor training and can help reduce the risk of falls by improving the static and dynamic balance [11; 17]. A key component to assess those at risk for falls must require the proper and necessary tools that accurately mimic and measure balance performance. In biomechanics research, force plates are instrumental devices that provide a detailed understanding of external forces acting against the body. These devices have provided meaningful insights in terms of clinical evaluations and have been used to assess sports performance, injury recovery, and rehabilitation. Investigation of balance ability has been characterized with measures created by the displacement from the center of pressure (COP). The COP is measured with a force platform, for example, while the participant performs quiet standing in double-leg, tandem, and single-leg stances. Balance control during these stances has been analyzed with the trajectory of the COP, or COP displacement time series. The COP displacement time series reflects the movement of the point location of the vertical ground reaction force vector; this vector represents the weighted average of all pressures of the surface area in contact with the support surface (ground). More commonly, studies have considered balance stability with the root mean square (RMS) of the medio-lateral (ML) and anterior-posterior (AP) COP displacement. Other measures include peak-to-peak displacement (MAXD) (i.e., maximum displacement in the ML and AP directions), total excursion (TE) (i.e., the total length of the COP path), and 95% confidence area (i.e., area which approximately 95% of the points on the COP path occupy) extracted from the COP measurements captured [18].