JMIR Publications

ABSTRACT

Background:

Visual representation is likely to affect the way people move. When playing virtual dodgeball in a prior study, greater excursion of the ankles, knees, hips, spine, and shoulder occur when presented in the 1st person perspective compared to the 3rd person perspective. However, the mode of presentation differed between the two conditions such that a head mounted display (HMD) was used to present the avatar in the 1st person perspective but a 3D television (3DTV) display was used to present the avatar was in the 3rd person. Thus, it is unknown whether changes in joint excursions are driven by visual display (HMD, 3DTV) or avatar perspective during virtual gameplay.

Objective:

To determine the influence of avatar perspective on joint excursion in healthy individuals playing virtual dodgeball game using a HMD.

Methods:

Participants (n=29, 15 male, 14 female) performed full-body movements to intercept launched virtual targets presented in a game of virtual dodgeball using a HMD. Two avatar perspectives were compared during each session of gameplay. A 1st person perspective was created by placing the center of the displayed content at the bridge of the participant’s nose, while a 3rd person perspective was created by placing the camera view at the participant’s eye level but set 1 meter behind the participant avatar. During gameplay, virtual dodgeballs were launched at a consistent velocity of 30 m/s to one of nine locations determined by a combination of three different intended impact heights and three different directions (left, center, or right) based on subject anthropometrics. Joint kinematics and angular excursions of the ankles, knees, hips, lumbar spine, elbows, and shoulders were captured.

Results:

The change in joint angles from initial posture to interception of virtual dodgeball were averaged across trials. Separate repeated measures ANOVAs revealed greater excursions of the ankle (p<0.001), knee (p<0.001), hip (p<0.005), spine (p<0.001), and shoulder (p<0.001) joints while playing virtual dodgeball in the 1st versus 3rd person perspective. Additionally, as expected, there was a significant effect of impact height on joint excursions.

Conclusions:

As clinicians develop treatment strategies to shape motion in orthopedic populations, it is important to be aware that changes in avatar perspective can significantly influence motor behavior. These data are important for the development of virtual reality assessment and treatment tools that are becoming increasingly practical for home and clinic-based rehabilitation.