In recent years, several multi-user virtual environments (VEs) have been developed to promote motivation and exercise intensity in motor rehabilitation. While competitive VEs have been extensively evaluated, collaborative and competitive rehabilitation VEs have seen relatively little study. Therefore, this article presents an evaluation of a VE for post-stroke arm rehabilitation that mimics everyday kitchen tasks and can be used either solo or collaboratively. Twenty subacute stroke survivors exercised with the VE for four sessions, with the first and third sessions involving solo exercise and the other two involving collaborative exercise. Exercise intensity was measured using inertial sensors while motivation was measured with questionnaires. Results showed high motivation and exercise intensity over all four sessions, and 11 of 20 participants preferred collaborative over solo exercise while only 4 preferred solo exercise. However, there were no differences in motivation, exercise duration, or exercise intensity between solo and collaborative sessions. Thus, we cannot currently claim that collaborative exercises are beneficial for upper limb rehabilitation. Future studies should evaluate other collaborative VE designs in different settings (e.g., at home) and with different participant pairs (e.g., patient-unimpaired) to find effective ways to utilize collaborative exercises in motor rehabilitation.
Stroke has been one of the leading causes of death worldwide for the past 15 years. Upper limb dysfunction is one of the main symptoms in stroke patients. The purpose of is to evaluate the treatment effectiveness of Immersive virtual reality system in upper limb rehabilitation. A single-blind clinical trial, and pretest–posttest control group design trial was conducted. The Fugl-Meyer Assessment of Physical Performance, Box and Block Test of Manual Dexterity, and FIM self-care score were used at baseline and post intervention. All subjects were asked to complete a total of twenty training sessions over eight weeks. The results of this project can be summarized as follows: (1) A total of eighteen stroke patients were involved in the trial, 15 males and 3 females, with an average age of 57.42 years (SD 12.75), and time from stroke (Mean 8.78 months, SD 5.51). (2) Results of the differences between the two groups pretest–posttest showed that the two groups were significantly differences in FMA (Conventional group, p = 0.021; Immersive virtual reality group, p = 0.014). It is known from the above results that the immersive virtual reality game device contributes to the improvement of the functions of the upper limbs. The results of this project are expected to provide a reference for innovative design in the medical industry and the entertainment industry.
McCrea, P.H., Eng, J.J., Hodgson, A.J.: Biomechanics of reachin: clinical implications for individuals with acquired brain injury. Disabil. Rehabil. 24, 534–541 (2002)CrossRefGoogle Scholar
Baldominos, A., Saez, Y., Pozo, C.G.: An approach to physical rehabilitation using state-of-the-art virtual reality and motion tracking technologies. Procedia Comput. Sci. 64, 10–16 (2015)CrossRefGoogle Scholar
Rose, T., Nam, C.S., Chen, K.B.: Immersion of virtual reality for rehabilitation – review. Appl. Ergonom. 69, 153–161 (2018)CrossRefGoogle Scholar
Huygelier, H., Schraepen, B., Ee, R., Abeele, V.V., Gillebert, C.R.: Acceptance of immersive headmounted virtual reality in older adults. Sci. Rep. 9, 4519 (2019)CrossRefGoogle Scholar
Gagliardi, C., et al.: Immersive virtual reality to improve walking abilities in cerebral palsy: a pilot study. Ann. Biomed. Eng. 46(9), 1376–1384 (2018)CrossRefGoogle Scholar
Lee, S.H., Jung, H.Y., Yun, S.J., Oh, B.M., Seo, H.G.: Upper extremity rehabilitation using fully immersive virtual reality games with a head mount display: a feasibility study. The Journal of Injury, Function and Rehabilitation (2019). https://doi.org/10.1002/pmrj.12206
Marsha Bisschop, A.G., et al.: Immersive virtual reality improves movement patterns in patients after ACL reconstruction: implications for enhanced criteria-based return-to-sport rehabilitation. Knee Surg. Sports Traumatol. Arthroscopy 24(7), 2280–2286 (2016)CrossRefGoogle Scholar
Jareda, A., Brianb, C., Justinc, D.: Immersive virtual reality in traumatic brain injury rehabilitation: a literature review. Neuro Rehabilit. 42(4), 441–448 (2018)Google Scholar
Sanford, J., Moreland, J., Swanson, L.R., Stratford, P., Gowiand, C.: Reliability of the fugl-meyer assessment for testing motor performance in patients following stroke. Phys. Ther. 73(7), 447–454 (1993)CrossRefGoogle Scholar
Ravaud, J.F., Delcey, M., Yelnik, A.: Construct validity of the functional independent measure (FIM): questioning the unidimensionality of the scale and the “value” of FIM scores. Scand. J. Rehabil. Med. 31(1), 31–41 (1999)CrossRefGoogle Scholar
The purpose of this study was to explore the clinical feasibility of virtual reality (VR) for the rehabilitation of upper limbs of stroke. In this study, it was found and suggested that future research should focus on the content design and application of VR rehabilitation games. While using VR to increase the interestingness of rehabilitation, one can also integrate VR and other technologies to achieve complementary benefits. In addition, in terms of the design of VR rehabilitation games, it was suggested that VR rehabilitation game researchers investigate the needs of the target users and design VR games that meet the needs of the target users in future work. Finally, this study demonstrates the clinical feasibility of applying VR technology for the rehabilitation of upper limbs after stroke, as well as highlights the aspects that still need to be addressed by researchers. These aspects are important targets of designing a VR system suitable for stroke upper limb rehabilitation.
Burdea, G.C., Coiffet, P.: Virtual Reality Technology, 2nd edn. Wiley, New York (2003)Google Scholar
Shirzad, N., Van der Loos, H.F.M.: Error amplification to promote motor learning and motivation in therapy robotics. In: 2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, San Diego, CA, pp. 3907–3910. IEEE (2012). https://doi.org/10.1109/EMBC.2012.6346821
Hatem, S.M., et al.: Rehabilitation of motor function after stroke: a multiple systematic review focused on techniques to stimulate upper extremity recovery. Front. Hum. Neurosci. 10, 442 (2016)CrossRefGoogle Scholar
Jiang, T.T., et al.: Analysis of virtual environment haptic robotic systems for a rehabilitation of post-stroke patients. In: 2017 IEEE International Conference on Industrial Technology (ICIT), Toronto, ON, pp. 738–742. IEEE (2017). https://doi.org/10.1109/ICIT.2017.7915451
Shi, P., et al.: A virtual reality training system based on upper limb exoskeleton rehabilitation robot. In: i-CREATe 2018: Proceedings of the 12th International Convention on Rehabilitation Engineering and Assistive Technology, pp. 138–141 (2018)Google Scholar
Cziksentmihalyi, M.: Flow – The Psychology of Optimal Experience (1990)Google Scholar
Flores, E., et al.: Improving patient motivation in game development for motor deficit rehabilitation. In: Proceedings of the 2008 International Conference in Advances on Computer Entertainment Technology – ACE 2008, Yokohama, Japan, p. 381. ACM Press (2008). https://doi.org/10.1145/1501750.1501839
Virtual reality video games, activity monitors, and handheld computer devices can help people stand as well as walk, the largest trial worldwide into the effects of digital devices in rehabilitation has found. The study was undertaken at hospitals in Sydney and Adelaide, Australia, and had 300 participants ranging from 18 to 101 years old. Those who exercised using digital devices in addition to their usual rehabilitation were found to have better mobility (walking, standing up, and balance) after 3 weeks and after 6 months than those who just completed their usual rehabilitation. The results were published in PLOS Medicine.
Trial participants were recovering from strokes, brain injuries, falls, and fractures. Participants used on average 4 different devices while in hospital and 2 different devices when at home. Fitbits were the most used digital device but also tested were a suite of devices like Xbox, Wii, and iPads, making the exercises more interactive and enabling remote connection between patients and their physical therapists. Having a selection meant the physical therapist could tailor the choice of devices to meet the patient’s mobility problems while considering patient preferences.
Lead author Leanne Hassett, PhD, from the Faculty of Medicine and Health at the University of Sydney, said benefits reported by patients using the digital devices in rehabilitation included variety, fun, feedback about performance, cognitive challenge, that they enabled additional exercise, and the potential to use the devices with others, such as family, therapists, and other patients. “These benefits meant patients were more likely to continue their therapy when and where it suited them, with the assistance of digital healthcare,” she said.
Participants reported doing more walking at 6 months, meaning their rehabilitation was improved, but this was not detected in the physical activity measure (time spent upright) generally. In the younger age group, the devices also increased daily step count. Distinctions between physical activity were made through measurements with an activPAL, a small device attached to the thigh that records how much time is spent in different positions (sitting, standing, lying) as well as number of steps taken each day.
This study used research physical therapists to deliver the study; the next step will be to trial the approach in clinical practice by incorporating it into the work of physical therapists.
The rehabilitation of cognitive and behavioral abnormalities in individuals with stroke is essential for promoting patient’s recovery and autonomy. The aim of our study is to evaluate the effects of robotic neurorehabilitation using Lokomat with and without VR on cognitive functioning and psychological well-being in stroke patients, as compared to traditional therapy.
Ninety stroke patients were included in this randomized controlled clinical trial. The patients were assigned to one of the three treatment groups, i.e. the Robotic Rehabilitation group undergoing robotic rehab with VR (RRG+VR), the Robotic Rehabilitation Group (RRG-VR) using robotics without VR, and the Conventional Rehabilitation group (CRG) submitted to conventional physiotherapy and cognitive treatment.
The analysis showed that either the robotic training (with and without VR) or the conventional rehabilitation led to significant improvements in the global cognitive functioning, mood, and executive functions, as well as in activities of daily living. However, only in the RRG+VR we observed a significant improvement in cognitive flexibility and shifting skills, selective attention/visual research, and quality of life, with regard to the perception of the mental and physical state.
Our study shows that robotic treatment, especially if associated with VR, may positively affect cognitive recovery and psychological well-being in patients with chronic stroke, thanks to the complex interation between movement and cognition.
A stroke is usually considered chronic at the six-month mark. This article reviews research on chronic stroke recovery and promising therapy treatment approaches that target improving limb function, even for an “old” stroke.
By Natalie Miller, Clinical Manager / Occupational Therapist. More posts by Natalie Miller.
27 MAR 2020 • 5 MIN READ
What is a chronic stroke?
The term chronic stroke typically refers to a time frame of at least six months after the initial stroke incident occurred. As a person enters this stage and moves onward to years of stroke survival, he may start to encounter all new frustrations related to recovery, especially regarding motor recovery and use of the affected arm.
In the medical world, “most significant” recovery of movement is generally considered to happen within the first six months, with spontaneous recovery slowing after that time. There is a push for high-intensity and high-frequency of therapy while the stroke is still fairly fresh, in order to capitalize on the “critical window” of the highest responsiveness to treatment.
That doesn’t mean we should stop addressing motor recovery after six months. What if we still focus on intensive therapy early on in stroke rehab, but also find ways to promote motor recovery six or more months later? What if we don’t stop searching for new strategies to improve, or at the very least, not lose function of the weaker arm?
Can I still improve function if I am in the chronic stage of stroke?
Our understanding of the brain and its capabilities is constantly evolving. We used to think that adult brains couldn’t change at all after a certain age! Emerging research evidence suggests there are ways to challenge and improve the chronic stroke brain months and even years down the road. One large-scale study involving outcomes from 219 stroke survivors suggested the critical window for motor recovery may be as long as 18 months! Another recent case study highlighted motor recovery in a stroke survivor who was 23 years post-stroke!
What types of rehabilitation are effective for people with chronic stroke?
Stroke research suggests the following treatments are promising for individuals who are at least six months post-stroke:
Mental Practice with Motor Imagery
Constraint Induced Movement Therapy (CIMT)
Virtual Reality (VR)
Preventing Learned Non-Use
Mental Practice with Motor Imagery
This is a type of treatment where a specific movement is rehearsed mentally. Done best with a pre-recorded audio set, the person listens carefully as a task is described in detail. The details usually include every aspect of that task, including how the five senses may be experienced while performing it, as well as the exact movements that would be needed to complete the task. For example, if the task were “drinking a cup of water,” the recording would describe how to reach out with the arm, extend the fingers, feel the weight of the cup, experience the temperature and the liquid as it touches the mouth, and the exactness of the motion to set it back down gently.
Studies have shown that with this type of repetitive visualization and practice, actual movement and functional use of the arm can improve, such that an arm that was once fairly “useless” can now actually pick up a water cup and bring it to the mouth. The best part is, research also shows that this can be an effective treatment 12 months and beyond since when the stroke actually happened!
Constraint Induced Movement Therapy (CIMT)
This is a type of treatment that involves blocking the stronger arm (usually with a cast or mitt) to promote engagement of the hemiplegic, or weaker arm. The more a person uses the weaker arm, the less they are at risk of “learned non-use.” By “forcing” the weaker arm to participate more, and even to be the primary or only source of function, it has a lot more chance to stay the same or get better, even years after the stroke happened. In fact, patients in Constraint Induced studies reported and showed increased use of their arms during normal activities, even if their strokes happened years before!
Virtual Reality (VR)
Virtual reality is another name for video games! This type of treatment may be immersive (using a headset) or non-immersive, with a participant engaging in a game on a screen. VR technology focusing on strengthening and improving limb function is becoming more prevalent in clinics and in homes. These programs are able to quantify arm or leg movement to control gameplay and provide immediate performance feedback.
Research supports the use of VR therapy to enhance motor recovery for adults with acute and chronic stroke. Virtual reality technology can also improve motivation in addition to movement outcomes, helping users stick with their self-training programs and continue using their affected side. Research shows that chronic stroke patients often find self-training programs that use video games to be user friendly and enjoyable.
Avoiding “learned non-use.”
We now know more about this phenomenon that affects many stroke survivors – especially those who are years out from a stroke. The stronger arm starts to take over to just get things accomplished, probably because there is a lot of positive feedback for using the stronger arm (It’s faster! It’s easier! I can just get it done!) and a lot of negative feedback for using the stroke-affected arm (It’s so frustrating! It takes me forever using it!). Research is showing that if people can still find motivation and dedication to actually trying to use the weaker arm, it is possible to still regain function – even years later.
The bottom line: don’t give up!
There IS hope. We can’t predict the exact amount of movement or strength that could come back, or what exactly you will be able to do with your affected arm or hand. But we are producing more research that is pointing us in the direction of believing recovery is still possible after that six month critical window. Don’t give up!
Ballester, BR, et al. (2019). A critical time window for recovery extends beyond one-year post-stroke. Journal of Neurophysiology, 122: 350-357. doi: 10.1152/jn.00762.2018 Soros, P, et al. (2017). Motor recovery beginning 23 years after ischemic stroke. Journal of Neurophysiology, 118(2): 778-781. doi: 10.1152/jn.00868.2016 Page, S, Levine, P, and Leonard, A. (2007). Mental practice in chronic stroke: results of a randomized, placebo-controlled trial. Stroke, 38(4): 1293-1297. doi: 10.1161/01.STR.0000260205.67348.2b Kunkel, A, et al. (1999). Constraint-induced movement therapy for motor recovery in chronic stroke patients. Archives of Physical Medicine and Rehabilitation, 80, 624-628. doi:10.1016/s0003-9993(99)90163-6 5. Taub, E, et al. (1993). Technique to improve chronic motor deficit after stroke. Archives of Physical Medicine and Rehabilitation, 74, 347-354. Subramanian, SK, et al. (2013). Arm motor recovery using a virtual reality intervention in chronic stroke: Randomized control trial. Neurorehabilitation and Neural Repair, 27(1), 13-23. doi: 10.1177/1545968312449695.
Introduction: Virtual reality (VR) are user-computer interface platforms that implement real-time simulation of an activity or environment, allowing user interaction via multiple sensory modalities. VR therapy may be an effective intervention for improving cognitive function following stroke. The aim of this systematic review was to examine the effectiveness of exercise-based VR therapy on cognition post-stroke.
Methods: Electronic databases were searched for terms related to “stroke”, “virtual reality”, “exercise” and “cognition”. Studies were included if they: (1) were randomized-controlled trials; (2) included VR-based interventions; (3) included individuals with stroke; and (4) included outcome measures related to cognitive function. Data from included studies were synthesised qualitatively and where possible, random effects meta-analyses were performed.
Results: Eight studies involving 196 participants were included in the review, of which five were included in meta-analyses (n = 124 participants). Studies varied in terms of type (combination of VR therapy and conventional therapy, combination of VR therapy and computer-based cognitive training, VR therapy alone) and duration of interventions (20–180 min), sample size (n = 12–42), length of the interventions (4–8 weeks), and cognitive outcomes examined. VR therapy was not more effective than control for improving global cognition (n = 5, SMD = 0.24, 95%CI:−0.30,0.78, p = .38), memory (n = 2 studies, SMD= 0.00, 95%CI: −0.58, 0.59, p = .99), attention (n = 2 studies, MD = 8.90, 95%CI: −27.89, 45.70, p = .64) or language (n = 2 studies, SMD = 0.56, 95%CI: −0.08,1.21, p = .09).
Conclusion: VR therapy was not superior to control interventions in improving cognition in individuals with stroke. Future research should include high-quality and adequately powered trials examining the impact of virtual reality therapy on cognition post-stroke.
Implications for rehabilitation
Virtual reality therapy is a promising new form of technology that has been shown to increase patient satisfaction towards stroke rehabilitation.
Virtual reality therapy has the added benefits of providing instant feedback, and the difficulty can be easily modified, underscoring the user-friendliness of this form of rehabilitation.
Virtual reality therapy has the potential to improve various motor, cognitive and physical deficits following stroke, highlighting its usefulness in rehabilitation settings.
Virtual reality (VR) games has the potential to improve patient outcomes in stroke rehabilitation. However, there is limited information on VR games as an adjunct to standard physiotherapy in improving upper limb function. This study involved 36 participants in both experimental (n = 18) and control (n = 18) groups with a mean age (SD) of 57 (8.20) and 63 (10.54) years, respectively. Outcome measures were the Fugl-Meyer assessment for upper extremities (FMA-UE), Wolf motor function test (WMFT), intrinsic motivation inventory (IMI), Lawton of instrumental activities of daily living (IADL), and stroke impact scale (SIS) assessed at pre-post intervention. The experimental group had 0.5 h of upper limb (UL) VR games with 1.5 h of standard physiotherapy, and the control group received 2 h of standard physiotherapy. The intervention for both groups was performed once a week for eight consecutive weeks. The results showed a significant time–group interaction effect for IMI (p = 0.001), Lawton IADL (p = 0.01) and SIS domain of communication (p = 0.03). A significant time effect was found in FMA-UE (p = 0.001), WMFT (p = 0.001), Lawton IADL (p = 0.01), and SIS domains; strength, ADL and stroke recovery (p < 0.05). These results indicated an improvement in UL motor ability, sensory function, instrumental ADL, and quality of life in both groups after eight weeks of intervention. However, no significant (p > 0.05) group effect on all the outcome measures was demonstrated. Thus, replacing a portion of standard physiotherapy time with VR games was equally effective in improving UL function and general health compared to receiving only standard physiotherapy among stroke survivors.
Stroke is a leading cause of significant disability among adults globally . Rehabilitation is of utmost importance with an increase in the number of stroke survivors . Stroke rehabilitation requires a multidisciplinary approach, is long-term and challenging due to its complexity . Recent evidence suggests that the extension of a stroke rehabilitation programme may lead to further improvement in function and quality of life among stroke survivors .
Persistent upper limb (UL) dysfunction after a stroke is one of the most challenging issues in rehabilitation . Increasing the dose of rehabilitation among stroke survivors may improve outcomes, and one of the strategies includes performing self-administered exercises using VR games technology . VR is a computer-assisted technology that can provide users with experiences of a simulated “real” environment . VR technology has been used in rehabilitation in addition to standard physiotherapy, or as a preventive therapy . VR-based rehabilitation also offers the capacity to individualise treatment needs while providing the standardisation of assessment and training protocols .
Earlier evidence suggested that VR technology can provide a unique medium whereby rehabilitation can be delivered in a functional and purposeful manner . Moreover, VR technology-based rehabilitation can be readily graded and documented . Other than that, stroke survivors can perform VR training at their home and the therapist can monitor from a distance, known as tele-rehabilitation . Compliance towards treatment and rehabilitation is a vital factor to consider in stroke management . Hence, VR rehabilitation has the potential to improve patient participation, enable intensive therapy and reduce demand on health care professionals [5,6,7].
In previous studies, VR games were shown to be effective in improving physical function among stroke survivors , balance and functional mobility in older adults [10,11], and upper limb reaction time in adults with physical disabilities . However, balance and mobility issues were examined rather than upper limb function [9,11]. There is also limited information on VR games as an adjunct to standard physiotherapy. Moreover, previous evidence mainly demonstrates the effects of VR as a standalone intervention among stroke survivors [13,14]. For example, in a pilot crossover design study involving 14 participants with chronic stroke, VR game-assisted intervention was performed for 45–60 min for a duration of 2.5 weeks . The results showed improved UL motor performance using the Fugl-Meyer assessment for upper extremities (FMA-UE) as the primary outcome measure. In our present study, we aimed to examine the effectiveness of VR games as an adjunct to standard physiotherapy in improving upper limb (UL) function and general health among stroke survivors.[…]
Stroke has increased in incidence worldwide. Although its mortality has reduced, it is the disease with the highest percentage of disability. For this reason, it is necessary to find new methods of rehabilitation and recovery from sequalae after a stroke, such as virtual reality (VR) therapy.
To analyse the effectiveness of VR as a rehabilitation therapy for movement improvement in adults after suffering a stroke.
A literature review was carried out through a systematic search in the PubMed, ScienceDirect and EBSCO databases (Medline Complete, Academic Search Complete, Academic Search Ultimate and E-Journal). A date restriction of the last five years and a language restriction in English and Spanish were applied.
A total of 13 studies met the inclusion/exclusion criteria and the objectives of this review. The selected studies compared conventional therapy (CT) with VR therapy, or CT with the combination of CT + VR, and other studies assessed VR effectiveness in isolation.
VR therapy would be effective for improving movement in post-stroke patients, either in isolation or as a complement to conventional therapy. The type of VR most used for stroke rehabilitation is the semi-immersive of second person that is generally applied six months after suffering a stroke. Unfortunately, it has not yet been possible to determine the efficacy of VR according to the brain region affected.
What was once a science fiction fantasy, virtual reality (VR) technology has evolved and come a long way. Together with augmented reality (AR) technology, these simulations of an alternative environment have been incorporated into rehabilitation treatments. The introduction of head-mounted displays has made VR/AR devices more intuitive and compact, and no longer limited to upper-limb rehabilitation. However, there is still limited evidence supporting the use of VR and AR technology during locomotion, especially regarding the safety and efficacy relating to walking biomechanics. Therefore, the objective of this study is to explore the limitations of such technology through gait analysis. In this study, thirteen participants walked on a treadmill in normal, virtual and augmented versions of the laboratory environment. A series of spatiotemporal parameters and lower-limb joint angles were compared between conditions. The center of pressure (CoP) ellipse area (95% confidence ellipse) was significantly different between conditions (p = 0.002). Pairwise comparisons indicated a significantly greater CoP ellipse area for both the AR (p = 0.002) and VR (p = 0.005) conditions when compared to the normal laboratory condition. Furthermore, there was a significant difference in stride length (p<0.001) and cadence (p<0.001) between conditions. No statistically significant difference was found in the hip, knee and ankle joint kinematics between the three conditions (p>0.082), except for maximum ankle plantarflexion (p = 0.001). These differences in CoP ellipse area indicate that users of head-mounted VR/AR devices had difficulty maintaining a stable position on the treadmill. Also, differences in the gait parameters suggest that users walked with an unusual gait pattern which could potentially affect the effectiveness of gait rehabilitation treatments. Based on these results, position guidance in the form of feedback and the use of specialized treadmills should be considered when using head-mounted VR/AR devices.
Over the past two decades, the application of virtual reality (VR) technology in a healthcare setting has become increasingly popular. It has been incorporated into clinical practices such as in the rehabilitation of stroke survivors, as well as patients with cerebral palsy and multiple sclerosis [1–3]. There is ample evidence suggesting that VR-based rehabilitation facilitates upper limb motion  and dynamic balance  among stroke survivors. More recently, research groups have also investigated the use of VR in dynamic situations (i.e. treadmill walking), aiming to improve balance and facilitate gait recovery [6–9].
In current clinical practice, gait retraining often includes treadmill training under the supervision of practitioners or through provision of real-time biofeedback. It is a widely adopted technique that aims to permanently correct faulty gait patterns and has been found to be effective in both walking and running gait modifications [10–12]. For example, a recently published randomized controlled trial showed that gait retraining was an effective intervention for reduction of knee loading and also improved symptoms among patients with early knee osteoarthritis . Incorporation of VR technology into conventional gait retraining has the potential to further enhance training outcomes. VR allows users to actively interact with a simulated environment in real-time and offers the opportunity to practice skills acquired in the virtual environments to everyday life . VR-based gait retraining has the potential to facilitate implicit learning, enhance variety, and actively engage the patient during training. These attributes are crucial in the optimization of motor learning and could maximize the training effect .
Walking is normally an automatic process. It has been suggested that conscious modification to walking patterns could affect gait retraining adaptations . A previous study found that subjects who trained with distraction were able to retain the training effect longer than the group who focused on correction . VR-based retraining could include different tasks and games while the patients modify their gait pattern as it could help patients to maintain focus and promote implicit motor learning. Moreover, the training environment, feedback type and level of difficulty of tasks can be manipulated within the VR environment relatively effortlessly for the clinician, as compared to conventional gait retraining. Variation in training has been shown to promote a more robust motor pattern and favor adaptation [16,17]. Moreover, motivation and adherence among patients can also be improved with more variation and an adjustable level of difficulty provided in the VR-based training . Stroke survivors were previously found to be more actively engaged in a VR-based training than a conventional task-oriented intervention to improve motor function . The training environment can be designed to simulate real-life activities and include task-specific training and a natural experience can be achieved through immersive VR devices, such as using a head-mounted display (HMD) . Studies have supported task-specific motor skill training with VR in helping to drive neuroplasticity in individuals with progressive neurodegenerative disorder [4,21].
Although multiple studies have reported positive results of gait retraining using VR among various patient groups within the lab [1,5,22,23], there is still little understanding of the limitations and challenges for using VR technology clinically. One overriding concern for using VR technology in clinical applications, especially an HMD, is safety. The user may not be able to recognize his/her own body position when using an immersive VR device, which could result in physical injuries, particularly if the user fails to stay within the boundaries of the treadmill. Suspension devices (i.e. an over-head harness) have been used for protection during VR-based gait rehabilitation , and a recent study showed that both young and older adults were able to use HMD during walking without adverse effects . However, the limit of VR technology on safety was not quantified or discussed. Recent technological advances in both the hardware and software of HMD might allow for safer use. However, there is still a need for evidence-based support and quantifiable data, which could help with practical considerations among VR applications in a clinical setting.
Another concern for gait rehabilitation would be the regularity and quality of gait. Through studying spatiotemporal gait parameters, some studies have reported that walking in a projected VR environment can induce gait instability even in healthy participants [24,25]. Nowadays, VR-based gait retraining using HMD focuses primarily on gait restoration after stroke ; the changes in natural gait due to the use of HMD may not be clinically significant. However, it is crucial for particular patient groups undergoing gait modification to maintain a certain level of regularity in their gait pattern. For instance, knee loading can be affected by spatiotemporal parameters such as cadence and step length  and VR was previously found to alter such parameters in an over-ground setting . The treatment effect of gait retraining in reducing knee loading would likely be affected if the patient’s baseline walking gait was already altered by the use of HMD or other VR devices. The aforementioned studies did not quantify the changes in walking biomechanics when using a HMD, therefore, this study aimed to identify gait parameters that were affected by the use of HMD.
An alternative to VR is Augmented Reality (AR), which does not fully immerse the user in a simulated environment but includes virtual elements that are superimposed on a real-world view . For example, external cues on foot placement could be overlaid on to the walking surface in order to facilitate gait adjustments [28,29]. The addition of feedback in AR-based gait retraining allows for variations in training and could enhance the gait retraining effect. Yet, there is also a lack of understanding of the limitation of using AR devices. Therefore, this study also aimed to examine the biomechanical changes induced by the HMD within an AR setting.
This study was designed to assess whether the use of commercially available HMD in VR and AR settings were suitable for clinical gait retraining. Specifically, the aim was to quantify the limitations of current VR and AR technology based on two practical concerns for clinical applications: 1) safety: the ability of the user to maintain a relatively stable position within the treadmill and 2) natural gait patterns: deviation of walking biomechanics from that of normal-treadmill walking. We hypothesized that there would be variations in the control of body position relative to the treadmill between both VR and AR conditions when compared with normal-treadmill walking. Also, based on altered gait biomechanics reported with the use of HMD in an over-ground setting , we hypothesized there would be variation in the spatiotemporal and joint kinematic measures while walking in VR and AR conditions, when compared with normal-treadmill walking.
Materials and methods
A total of 13 participants (7 females, 6 males; age = 24.6 ± 4.5 years; weight = 63.1 ± 14.5 kg; height = 1.68 ± 0.11 m) were recruited for this study through convenient sampling, which is a comparable sample size to previous studies [30–32]. Participants were free of any musculoskeletal, neurological, neuromuscular or cardiovascular pathology that might hinder walking. The experimental procedures were reviewed and approved by the Departmental Research Committee of the department of Rehabilitation Sciences, The Hong Kong Polytechnic University (Ref.: HSEARS20161018001) and written informed consent was obtained from all participants prior to the experiment.
Participants were asked to walk at a self-selected pace for four minutes to allow for treadmill adaptation prior to data collection . Anthropometric data, including leg length, knee width and ankle width [34–36], were recorded and 39 reflective markers were affixed to specific bony landmarks based on the Vicon Plug-in-Gait® full body model . The marker model was previously established for the measurement of lower-limb kinematics . This study was designed to assess HMD in VR and AR settings using a commercially available model within a typical clinical setting. Thus, the conditions were designed to be simple and without the use of additional lab equipment. All walking trials were conducted on a dual-belt instrumented treadmill (Force-sensing tandem treadmill, AMTI, Watertown, MA, USA; length x width = 1.2 x 0.6 m). Participants wore their own usual shoes and walked under different conditions at 3.0 km/h (0.83 m/s) for three minutes each. The three conditions were Control, VR and AR, details were as follows:
Control: Treadmill walking without the HMD;
Virtual reality (VR): Immersive 360° panoramic image of the laboratory captured by the Samsung Gear 360 Cam (Samsung, Seoul, South Korea), set up instructions and image file used are provided in the supporting information (S1 File and S1 Fig).
Augmented reality (AR): Real-time display through the rear camera of the HMD, set up instructions are provided in the supporting information (S2 File).
For the AR and VR conditions, participants wore a head-mounted VR device (Samsung Gear VR SM-R322 and Samsung Galaxy S7, Samsung, Seoul, South Korea; width x height x depth: 201.93 x 92.71 x 116.33 mm). The immersive VR/AR environment within this study refers to the panoramic display in a first-person perspective with complete visual obstruction to the real-world environment. The HMD used in this study weighs a total of 470 g, which is comparable to typical commercial HMD models (HTC VIVE Pro: 555 g  and Oculus Rift DK2: 440 g ). Adjustments to the device were made for fit, focus, and orientation for each participant. Participant’s comfort was confirmed through subjective reporting before the beginning of each walking trial.
The test sequence was randomized using a web-based software (www.randomizer.org). To ensure safety, participants were supported by an overhead safety harness providing 0% bodyweight support. The experimental setup is indicated in Fig 1. The individual in Fig 1 of this manuscript has given written informed consent (as outlined in PLOS consent form) to publish the photograph.
Fig 1 A photograph to illustrate the experimental setup.For condition AR and VR, the participant wore a head-mounted VR device. The participant was protected by an overhead safety harness system. Reflective markers and motion cameras were employed to collect gait biomechanics during the walking trials.