Effects of Real-World Versus Virtual Environments on Joint Excursions in Full-Body Reaching Tasks

Abstract

Starting from an upright standing posture and reaching for a target that requires some forward bending of the trunk can involve many different configurations of the trunk and limb segments. We sought to determine if configurations of the limb and trunk segments during our standardized full-body reaching tasks were influenced by the visual environment. This paper examined movement patterns of healthy participants (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$n=17$ \end{document}, eight female and nine male) performing full body reaching tasks to: 1) real-world targets; 2) virtual targets presented on a 3-D television; and 3) virtual targets presented using a head-mounted display. For reaches performed in the virtual world, the avatar was presented from a third-person perspective for the 3-D television and from a first-person perspective for the head-mounted display. Reaches to virtual targets resulted in significantly greater excursions of the ankle, knee, hip, spine, and shoulder compared with reaches made to real-world targets. This resulted in significant differences in the forward and downward displacements of the whole-body center of mass between the visual environments. Visual environment clearly influences how subjects perform full-body reaching tasks to static targets. Because a primary goal of virtual reality within rehabilitation is often to restore movement following orthopedic or neurologic injury, it is important to understand how visual environment will affect motor behavior. The present findings suggest that the existing game systems that track and present avatars from a third-person perspective elicit significantly different motor behavior when compared with the same tasks being presented from a first-person perspective.

Role of Virtual Reality in Balance Training in Patients with Spinal Cord Injury: A Prospective Comparative Pre-Post Study

“…Full body reaching tasks to virtual targets results in greater joint excursions as compared to real-world targets. Without the actual physical end-point, one can thus move beyond the visual target [8,14,19]. This explains the improvement in POMA-B in the EG in our study.…”

Effects of Avatar Perspective on Joint Excursions Used to Play Virtual Dodgeball: Within-Subject Comparative Study

“…Each game level consisted of 2 sets with 15 balls in each set. The intended impact locations of 12 of the 15 balls launched were distributed amongst the three impact heights normalized to the participant’s arm length, trunk length, and hip height [ 8 , 9 , 13 - 16 ]. For example, during gameplay, the participant could successfully block a virtual ball launched to impact height 1 (ie, IH1, the highest impact height) simply by flexing at the lumbar spine 15° with the elbow fully extended and the shoulder flexed to 90°.…”

“…However, the vast differences in methodology, especially concerning visual display type, avatar perspective, and level of gameplay immersion, make it difficult to draw broad conclusions about which features are driving the efficacy of VR treatments [ 7 ]. Visual environments in VR can present 3-dimensional (3D) images across a variety of display devices, including head mounted-displays (HMD) [ 6 ] and 3D televisions (3DTV) [ 8 , 9 ]. The different methods used to present visual scenes can affect how the virtual environment is perceived and thus can influence not only motor behavior [ 8 ] but pain responses as well [ 10 ].…”

“…While Thomas and colleagues have shown that avatar perspective influences joint excursions in full-body reaching tasks [ 9 ] as well as during VR gameplay [ 8 ], it is unknown if the differences in joint excursions were driven by avatar perspective (first- or third-person) or by display type (HMD or 3DTV). Ustinova et al [ 11 ] reported that individuals reached further and preferred tasks when the camera perspective was oriented at angles from 45 to 77.5 degrees relative to the location of the avatar as compared to the camera oriented at zero degrees (ie, directly behind the avatar) [ 11 ].…”

“…This study was designed to determine the effects of avatar perspective (ie, first- versus third-person) on joint excursions of healthy participants engaged in full-body movements during a VR dodgeball game presented on an HMD. Based on existing studies [ 8 , 9 , 11 ], we predicted that joint excursions would be greater in the first person versus third-person perspective.…”