A Virtual Physical Therapy Lab to Simulate a Balance Perturbation Assessment Setup

Maintaining postural balance is crucial in humans due to the inherent instability associated with high center of mass and small base of support while standing and walking.  Hence, a loss of balance is a common occurrence amongst elderly people, and in individuals with musculo-skeletal and neurological disorders. Furthermore, a loss in balance might lead to falls and fall-related injuries that might considerably increase emergency hospital visits and have a high economic cost.

Currently, there are many laboratory-based tests available for investigating balance while walking. However, there aren’t many dynamic balance systems that measure the perturbation to the upper torso while standing, since most tests measure lower extremity perturbations in both static and dynamic situations.

 Our study addresses the development of a virtual lab in an immersive CAVE system (Visbox, Inc., IL) to simulate an upper body balance perturbation unit. The primary goal of the study is to determine if virtual reality (VR) perturbation could be effectively used for balance assessment instead of a physical setup. We validate the Virtual Balance-Perturbation-Setup (VBPS) against a Physical Balance-Perturbation-Setup (PBPS) present in the physical therapy lab. The PBPS includes a seven-and-a-half-foot apparatus with a height-adjustable pendulum (a swinging central rod with the distal end designed as two padded pieces physically perturbing the subject at the shoulder level [1]. This PBPS is reconfigurable and can be adjusted to the subject’s height and shoulder width. We developed the VBPS that utilizes Unity 3D and Blender software to recreate the visual environment of the Physical Therapy (PT) lab and is rendered in an immersive CAVE Virtual Reality Environment (CAVE) system integrated with a motion capture system. A haptic vest equipped with tactors is used to simulate the force feedback on the subject’s upper torso/shoulder. The simulation of the VBPS is aligned with the motion capture that detects the shoulder position and in-turn activates the tactors on the haptic vest, creating a simulated sensation of being perturbed by the virtual pendulum. This virtual VBPS for balance assessment is expected to be assessed for its effectiveness as compared to the experimental setup using appropriate kinematic measures and sensors. Thus, the purpose of the experiment is to validate virtual VBPS against the physical PBPS. The virtual lab has the potential to provide an alternate, highly automatic and reconfigurable method for physical therapy assessments of balance leading to rapid development of future balance training strategies for individualized care.

References

Krishnan V, Aruin A, Latash ML (2011) Two stages and three components of the postural preparation to action. Experimental Brain Research 212(1):47-63