Assessing the Perception of Trunk Movements in Military Personnel with Chronic Non-Specific Low Back Pain Using a Virtual Mirror

Abstract

Chronic pain, including chronic non-specific low back pain (CNSLBP), is often associated with body perception disturbances, but these have generally been assessed under static conditions. The objective of this study was to use a “virtual mirror” that scaled visual movement feedback to assess body perception during active movement in military personnel with CNSLBP (n = 15) as compared to military healthy control subjects (n = 15). Subjects performed a trunk flexion task while sitting and standing in front of a large screen displaying a full-body virtual mirror-image (avatar) in real-time. Avatar movements were scaled to appear greater, identical, or smaller than the subjects’ actual movements. A total of 126 trials with 11 different scaling factors were pseudo-randomized across 6 blocks. After each trial, subjects had to decide whether the avatar’s movements were “greater” or “smaller” than their own movements. Based on this two-alternative forced choice paradigm, a psychophysical curve was fitted to the data for each subject, and several metrics were derived from this curve. In addition, task adherence (kinematics) and virtual reality immersion were assessed. Groups displayed a similar ability to discriminate between different levels of movement scaling. Still, subjects with CNSLBP showed an abnormal performance and tended to overestimate their own movements (a right-shifted psychophysical curve). Subjects showed adequate task adherence, and on average virtual reality immersion was reported to be very good. In conclusion, these results extend previous work in patients with CNSLBP, and denote an important relationship between body perception, movement and pain. As such, the assessment of body perception during active movement can offer new avenues for understanding and managing body perception disturbances and abnormal movement patterns in patients with pain.

Exploring the Relationships Between Altered Body Perception, Limb Position Sense, and Limb Movement Sense in Complex Regional Pain Syndrome

“…Previous studies have suggested that perception of the body and its movements are biased in the presence of chronic pain-for example, showing that the subjective body midline in CRPS is shifted toward the painful side 34 or that trunk flexion movements are overestimated in chronic low back pain. 27 In contrast with these observations, we did not find a perceptive bias in the assessment of kinesthesia in CRPS. Indeed, no interaction between group and error direction was observed in task 1, which does not indicate a bias toward larger errors on the x-axis in the CRPS group relative to controls.…”

“…The sense of limb movement was evaluated as described by Roosink et al 27,28 First, results obtained with the 2-alternative forced choice paradigm (greater = 1, smaller = 0) were plotted against the 13 scaling factors (log-transformed to be on a linear scale). Second, a sigmoid curve (1), with initial values X Y.50 = 0, constraints Y MAX = 1 and Y MIN = 0, and a variable slope (m), was fitted to the data using Prism 6 for Windows (GraphPad Software, La Jolla, CA):…”

“…1,7 However, only 1 previous study has assessed the sense of limb movement during active movement and found that individuals with chronic low back pain tend to overestimate their trunk flexion compared with painfree controls. 27 Importantly, in that study, the flexionextension movement was continuous, to ensure that judgment relied on a continuous comparison between sensory input and motor output rather than on a comparison of final (static) postures. 27 The observed alterations of body perception and kinesthesia (ie, the senses of limb position and limb movement 26 ) in various populations of individuals with chronic pain raises the question of whether these 3 variables are related.…”

“…27 Importantly, in that study, the flexionextension movement was continuous, to ensure that judgment relied on a continuous comparison between sensory input and motor output rather than on a comparison of final (static) postures. 27 The observed alterations of body perception and kinesthesia (ie, the senses of limb position and limb movement 26 ) in various populations of individuals with chronic pain raises the question of whether these 3 variables are related. Surprisingly, no study to date has assessed such associations in chronic pain.…”

A Multi Platform Pain Assessment Tool using Bespoke Gaming Sensors

“…In the study of Roosink et al [20], a Virtual Mirror is employed for a task specific intervention undertaken by participants suffering from nonspecific low back pain to assess the correlation between body and motion perception and perception disturbances due to pain.…”