Evaluating adaptiveness of an active back exosuit for dynamic lifting and maximum range of motion.

Back exosuits deliver mechanical assistance to reduce the risk of back injury, however, minimising restriction is critical for adoption. We developed the adaptive impedance controller to minimise restriction while maintaining assistance by modulating impedance based on the user's movement direction and nonlinear sine curves. The objective of this study was to compare active assistance, delivered by a back exosuit via our adaptive impedance controller, to three levels of assistance from passive elastics. Fifteen participants completed five experimental blocks (4 exosuits and 1 no-suit) consisting of a maximum flexion and a constrained lifting task. While a higher stiffness elastic reduced back extensor muscle activity by 13%, it restricted maximum range of motion (RoM) by 13°. The adaptive impedance approach did not restrict RoM while reducing back extensor muscle activity by 15%, when lifting. This study highlights an adaptive impedance approach might improve usability by circumventing the assistance-restriction trade-off inherent to passive approaches.Practitioner summary: This study demonstrates a soft active exosuit that delivers assistance with an adaptive impedance approach can provide reductions in overall back muscle activity without the impacts of restricted range of motion or perception of restriction and discomfort.

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

BACKGROUND: Visual representation of oneself is likely to affect movement patterns. Prior work in virtual dodgeball showed greater excursion of the ankles, knees, hips, spine, and shoulder occurs when presented in the first-person perspective compared to the third-person perspective. However, the mode of presentation differed between the two conditions such that a head-mounted display was used to present the avatar in the first-person perspective, but a 3D television (3DTV) display was used to present the avatar in the third-person. Thus, it is unknown whether changes in joint excursions are driven by the visual display (head-mounted display versus 3DTV) or avatar perspective during virtual gameplay. OBJECTIVE: This study aimed to determine the influence of avatar perspective on joint excursion in healthy individuals playing virtual dodgeball using a head-mounted display. 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 head-mounted display. Two avatar perspectives were compared during each session of gameplay. A first-person perspective was created by placing the center of the displayed content at the bridge of the participant's nose, while a third-person perspective was created by placing the camera view at the participant's eye level but set 1 m 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 assessed. RESULTS: The change in joint excursions from initial posture to the interception of the virtual dodgeball were averaged across trials. Separate repeated-measures ANOVAs revealed greater excursions of the ankle (P=.010), knee (P=.001), hip (P=.0014), spine (P=.001), and shoulder (P=.001) joints while playing virtual dodgeball in the first versus third-person perspective. Aligning with the expectations, there was a significant effect of impact height on joint excursions. CONCLUSIONS: As clinicians develop treatment strategies in virtual reality 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.

Sørensen test performance is driven by different physiological and psychological variables in participants with and without recurrent low back pain.

Time to task failure (TTF) on the Sørensen test predicts low back pain (LBP), but mechanisms driving TTF may vary in those with and without recurrent LBP. To determine the physiological and psychological predictors of TTF, 48 sex, age, and BMI matched participants (24 Healthy, 24 LBP) completed psychological surveys, maximal strength assessments, and the Sørensen test. A two-way ANOVA revealed no significant effects of group (p = 0.75) or sex (p = 0.21) on TTF. In the full sample, linear regression analyses revealed that normalized Median Power Frequency (MPF) slope of the Erector Spinae (ß = 0.350, p < 0.01), the Biceps Femoris (ß = 0.375, p < 0.01), and self-efficacy (ß = 0.437, p < 0.01) predicted TTF. In the Healthy group, normalized MPF slope of the Erector Spinae (ß = 0.470, p < 0.01), the Biceps Femoris (ß = 0.437, p < 0.01), and self-efficacy (ß = 0.330, p = 0.02) predicted TTF. In the LBP group, trunk mass (ß = -0.369, p = 0.04) and self-efficacy (ß = 0.450, p = 0.02) predicted TTF. In sum, self-efficacy consistently predicts performance, while trunk mass appears to negatively influence TTF only for those with recurrent LBP.

Determining Physiological and Psychological Predictors of Time to Task Failure on a Virtual Reality Sørensen Test in Participants With and Without Recurrent Low Back Pain: Exploratory Study.

BACKGROUND: Sørensen trunk extension endurance test performance predicts the development of low back pain and is a strong discriminator of those with and without low back pain. Performance may greatly depend on psychological factors, such as kinesiophobia, self-efficacy, and motivation. Virtual reality video games have been used in people with low back pain to encourage physical activity that would otherwise be avoided out of fear of pain or harm. Accordingly, we developed a virtual reality video game to assess the influence of immersive gaming on the Sørensen test performance. OBJECTIVE: The objective of our study was to determine the physiological and psychological predictors of time to task failure (TTF) on a virtual reality Sørensen test in participants with and without a history of recurrent low back pain. METHODS: We recruited 24 individuals with a history of recurrent low back pain and 24 sex-, age-, and body mass index-matched individuals without a history of low back pain. Participants completed a series of psychological measures, including the Center for Epidemiological Studies-Depression Scale, Pain Resilience Scale, Pain Catastrophizing Scale, Tampa Scale for Kinesiophobia, and a self-efficacy measure. The maximal isometric strength of trunk and hip extensors and TTF on a virtual reality Sørensen test were measured. Electromyography of the erector spinae, gluteus maximus, and biceps femoris was recorded during the strength and endurance trials. RESULTS: A two-way analysis of variance revealed no significant difference in TTF between groups (P=.99), but there was a trend for longer TTF in females on the virtual reality Sørensen test (P=.06). Linear regression analyses were performed to determine predictors of TTF in each group. In healthy participants, the normalized median power frequency slope of erector spinae (beta=.450, P=.01), biceps femoris (beta=.400, P=.01), and trunk mass (beta=-.32, P=.02) predicted TTF. In participants with recurrent low back pain, trunk mass (beta=-.67, P<.001), Tampa Scale for Kinesiophobia (beta=-.43, P=.01), and self-efficacy (beta=.35, P=.03) predicted TTF. CONCLUSIONS: Trunk mass appears to be a consistent predictor of performance. Kinesiophobia appears to negatively influence TTF for those with a history of recurrent low back pain, but does not influence healthy individuals. Self-efficacy is associated with better performance in individuals with a history of recurrent low back pain, whereas a less steep median power frequency slope of the trunk and hip extensors is associated with better performance in individuals without a history of low back pain.

A randomized control trial to determine the effectiveness and physiological effects of spinal manipulation and spinal mobilization compared to each other and a sham condition in patients with chronic low back pain: Study protocol for The RELIEF Study.

BACKGROUND: Low back pain (LBP) is one of the most common reasons for seeking medical care. Manipulative therapies are a common treatment for LBP. Few studies have compared the effectiveness of different types of manipulative therapies. Moreover, the physiologic mechanisms underlying these treatments are not fully understood. Herein, we present the study protocol for The Researching the Effectiveness of Lumbar Interventions for Enhancing Function Study (The RELIEF Study). METHODS AND STUDY DESIGN: The RELIEF Study is a Phase II RCT with a nested mechanistic design. It is a single-blinded, sham-controlled study to test the mechanisms and effectiveness of two manual therapy techniques applied to individuals (n = 162; 18-45 years of age) with chronic LBP. The clinical outcome data from the mechanistic component will be pooled across experiments to permit an exploratory Phase II RCT investigating the effectiveness. Participants will be randomized into one of three separate experiments that constitute the mechanistic component to determine the muscular, spinal, and cortical effects of manual therapies. Within each of these experimental groups study participants will be randomly assigned to one of the three treatment arms: 1) spinal manipulation, 2) spinal mobilization, or 3) sham laser therapy. Treatments will be delivered twice per week for 3-weeks. DISCUSSION: This data from this will shed light on the mechanisms underlying popular treatments for LBP. Additionally, the coupling of this basic science work in the context of a clinical trial will also permit examination of the clinical efficacy of two different types of manipulative therapies.

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

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 ([Formula: see text], 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.

Feasibility and Safety of a Virtual Reality Dodgeball Intervention for Chronic Low Back Pain: A Randomized Clinical Trial.

Whereas the fear-avoidance model of chronic low back pain (CLBP) posits a generic avoidance of movement that is perceived as threatening, we have repeatedly shown that individuals with high fear and CLBP specifically avoid flexion of the lumbar spine. Accordingly, we developed a virtual dodgeball intervention designed to elicit graded increases in lumbar spine flexion while reducing expectations of fear and harm by engaging participants in a competitive game that is entertaining and distracting. We recruited 52 participants (48% female) with CLBP and high fear of movement and randomized them to either a game group (n = 26) or a control group (n = 26). All participants completed a pregame baseline and a follow-up assessment (4-6 days later) of lumbar spine motion and expectations of pain and harm during standardized reaches to high (easier), middle, and low (hardest to reach) targets. For 3 consecutive days, participants in the game group completed 15 minutes of virtual dodgeball between baseline and follow-up. For the standardized reaching tests, there were no significant effects of group on changes in lumbar spine flexion, expected pain, or expected harm. However, virtual dodgeball was effective at increasing lumbar flexion within and across gameplay sessions. Participants reported strong positive endorsement of the game, no increases in medication use, pain, or disability, and no adverse events. Although these findings indicate that very brief exposure to this game did not translate to significant changes outside the game environment, this was not surprising because graded exposure therapy for fear of movement among individuals with low back pain typically last 8 to 12 sessions. Because of the demonstration of safety, feasibility, and ability to encourage lumbar flexion within gameplay, these findings provide support for a clinical trial wherein the treatment dose is more consistent with traditional graded exposure approaches to CLBP. PERSPECTIVE: This study of a virtual reality dodgeball intervention provides evidence of feasibility, safety, and utility to encourage lumbar spine flexion among individuals with CLBP and high fear of movement.

Effects of Visual Display on Joint Excursions Used to Play Virtual Dodgeball.

BACKGROUND: Virtual reality (VR) interventions hold great potential for rehabilitation as commercial systems are becoming more affordable and can be easily applied to both clinical and home settings. OBJECTIVE: In this study, we sought to determine how differences in the VR display type can influence motor behavior, cognitive load, and participant engagement. METHODS: Movement patterns of 17 healthy young adults (8 female, 9 male) were examined during games of Virtual Dodgeball presented on a three-dimensional television (3DTV) and a head-mounted display (HMD). The participant's avatar was presented from a third-person perspective on a 3DTV and from a first-person perspective on an HMD. RESULTS: Examination of motor behavior revealed significantly greater excursions of the knee (P=.003), hip (P<.001), spine (P<.001), shoulder (P=.001), and elbow (P=.026) during HMD versus 3DTV gameplay, resulting in significant differences in forward (P=.003) and downward (P<.001) displacement of the whole-body center of mass. Analyses of cognitive load and engagement revealed that relative to 3DTV, participants indicated that HMD gameplay resulted in greater satisfaction with overall performance and was less frustrating (P<.001). There were no significant differences noted for mental demand. CONCLUSIONS: Differences in visual display type and participant perspective influence how participants perform in Virtual Dodgeball. Because VR use within rehabilitation settings is often designed to help restore movement following orthopedic or neurologic injury, these findings provide an important caveat regarding the need to consider the potential influence of presentation format and perspective on motor behavior.