Hand-Arm Bimanual Intensive Training in Virtual Reality: A Feasibility Study : Pediatric Physical Therapy

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RESEARCH REPORTS

Hand-Arm Bimanual Intensive Training in Virtual Reality: A Feasibility Study

Gehringer, James E. PhD; Fortin, Elizabeth DPT, PCS; Surkar, Swati M. PT, PhD; Hao, Jie PT, DPT; Pleiss, Monica OTD, OTR/L, BCP; Jensen-Willett, Sandra PT, PhD, PCS

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Pediatric Physical Therapy 35(1):p 85-91, January 2023. | DOI: 10.1097/PEP.0000000000000975
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Abstract

INTRODUCTION AND PURPOSE

One successful therapy technique used to improve the upper extremity motor actions of children with unilateral cerebral palsy (CP) is hand-arm bimanual intensive training (HABIT). Endorsed by Novak et al1 as a “green light” therapy with substantive clinical trial data demonstrating a strong positive result, HABIT is an intensive intervention directed at improving bimanual coordination and function of the more affected arm. HABIT uses age-appropriate fine and gross motor bimanual activities delivered within the context of play. This approach has been effective in improving Assisting Hand Assessment (AHA) and Box and Blocks Test (BBT) scores, suggesting improvements in the affected hand/arm function, bimanual coordination, and gross motor skill.2–5

However, to improve the upper extremity motor actions, HABIT often requires a training dose ranging from 30 to 90 hours during 5 to 10 days of high-repetition, motor-learning–based activities. This intensive therapy often leads to frustration and lack of motivation in children with CP, leading to lower therapeutic outcomes due to reduced participation.5 In addition, due to the time and resources required to perform HABIT in a camp-based approach, its utility is often limited in the number of children who may participate and how frequently these camps are held. For these reasons, HABIT camps are not held regularly and often support a smaller cohort of children, which further suggests that HABIT is often inaccessible for families and children who may benefit from the camp.6,7 Therefore, new ways must be explored to increase the child's engagement and access to the treatment.

Virtual reality (VR) is a rapidly advancing technology that has been used to augment therapy for children with CP, increasing their motivation and maximizing therapeutic outcomes.8 Virtual reality has been a focus of new interventions because of its effect on neuroplasticity.9 Virtual reality training has resulted in improvements in balance and gait in individuals with CP.10 Recent investigations suggest that upper extremity therapy augmented with VR can lead to functional improvements in people with CP.11 Furthermore, Hung and Gordon12 suggested that VR technology could become a part of the therapy regimen for people with CP, as commercial VR systems have become more available and are accessible in the home. Using a commercial VR system as a therapy tool in the home enables greater access for those who may not be able to attend such intensive therapy camp13 and provides a method for continuous care and higher dosage, which leads to greater upper extremity improvements.14 However, the use of low-cost, immersive VR systems for upper extremity HABIT-style therapy has yet to be evaluated.

DESIGN CONSIDERATIONS

HABIT in VR (HABIT-VR) was designed to incorporate evidence-based motor-learning principles and gamified bimanual tasks into commercially available VR hardware. These games were designed by an interdisciplinary team of physical therapists, occupational therapists, neuroscientists, and engineers, and were based on tasks performed in HABIT camps4 and other movements commonly practiced in our occupational and physical therapy clinics. A commercial VR system, the Oculus Quest, was chosen as the development platform because the device is low cost for a VR headset and the systems come with 2 controllers that track hand movement through 3-dimensional (3D) space. With this hardware system, standard HABIT tasks were transformed into video games where bimanual function was a strict task constraint.

Once VR games were prototyped, we conducted testing sessions with people with CP that were receiving clinical services and did not participate in the camp. During these sessions, the development and clinical teams observed the player. Both the player and the clinicians present were asked questions about their experience and observations. The feedback was then incorporated into the next iteration of designs. Often, we received feedback from the participating children about the need for more accessibility options and adding gamified features to increase engagement and the replay value. Feedback from the clinicians focused on the user experience/success, how the movements required in each game might be scaled, and how these movements might be linked to real-world tasks. This iterative design with live play testing is typical in serious game development and was instrumental in making sure that these games incorporated both features to drive player engagement and the scalable motor-learning principles to maximize motor-learning outcomes.

Each game was designed to incorporate the following motor learning principles: self-generated active movements, high-intensity practice of bimanual tasks, and practice directly targeting the achievement of a goal set by the child or the parent. These HABIT principles were combined with assistive technology VR and gaming, which Novak et al1 consider a yellow-light therapy or a weak positive motor intervention. A major reason for this “weak positive” ranking is that children found gamified therapies rewarding and normalizing. This was an important consideration for HABIT-VR as it was designed to increase motivation and attention, which are vital modulators for neuroplasticity.15 Furthermore, children find successful task-specific practice rewarding and enjoyable.15 The HABIT-VR games were designed to provide immediate and clear feedback to the children, which facilitates motor learning, and to introduce novelty, which facilitates neuroplasticity. Surprising or unexpected visual and auditory effects supplement routine feedback associated with task performance.16

HABIT-VR was designed to ensure that the games were accessible for children with CP to play, and that task difficulty was modifiable to meet the correct challenge point. Being able to scale the task to the child's ability level is important to drive motor learning.15 In addition, perceived challenge is associated with the enjoyment of a task,17 an important aspect of long-term engagement. To accommodate the heterogeneity of motor and cognitive challenges inherent with various presentations in CP, accessibility options were included that could scale the motor and cognitive difficulty of the games to promote the just right challenge.18

The accessibility options that scaled the difficulty of the motor actions offered options to change the direction of movement, the speed of movement, or how objects were interacted within the game. It also allowed the player to be repositioned in the 3D environment or reset the game to the original state while maintaining the player's score, if an unexpected interaction occurred. Every participant used a scalability option: “Touch Mode.” This option, inspired by “sticky mittens,”19 allowed participants to make contact with the virtual object to pick it up and manipulate it. “Touch Mode” simplified the task, promoted initial success, and prevented frustration if the participant was unable to trigger the Oculus controller.

The accessibility options that scaled the difficulty of the cognitive task included activating/deactivating cognitive challenges, changing the goal of the game, and changing task complexity by modifying the amount of information needed for success. HABIT-VR added cognitive challenges to the motor tasks, as providing cognitive opportunities is an important ingredient in successful motor-learning paradigms18 and addresses a limitation often seen in assistive technology VR and gaming. Using commercial video games in clinical settings may not be engaging for children as difficulty options often scale cognitive and motor aspects of the task uniformly. For children with CP, this may make the task daunting and increase frustration; or there may be disparities between motor and cognitive abilities that prevent success.20 When motor and cognitive difficulty scaling is uniform, it may mean that the difficulty level is set incorrectly for either the cognitive or motor developmental levels. If either difficulty level is set incorrectly, the child may become frustrated or bored, and the number of repetitions needed to see motor improvements will not be performed. HABIT-VR's cognitive scaling options enabled the clinicians to focus cognitive resources on the motor task alone to ensure initial success and add in cognitive challenges later to encourage long-term engagement.

HYPOTHESES

In the present study, HABIT-VR was used as part of a HABIT camp to evaluate the feasibility of using VR software within a traditional HABIT camp setting. Although both HABIT and VR therapies have shown positive results for children with CP, HABIT-VR itself has not been used for clinical purposes; thus, it is unclear whether it is feasible to use this software. Our key hypotheses were that (1) the functional and bimanual motor skills of the participants would significantly improve after participating in a camp that uses a combination of traditional HABIT and therapeutic VR software, and (2) the gross and fine motor skills of the participants would improve after participating in a camp that uses a combination of traditional HABIT and therapeutic VR software.

METHODS

Participants

Eight children with CP (age = 7.1 ± 2.3 years; female = 3; 7 with unilateral CP, 1 with bilateral CP; right hand dominant = 4; Manual Ability Classification System [MACS] score level = 1 I, 3 II, 3 III, 1 IV) were enrolled in this study. Inclusion criteria were children diagnosed as with CP having MACS between I and IV. Exclusion criteria were children with any other conditions leading to inability to move the upper extremity or handle objects and children with known visual impairments that would affect visual gaze and visual tracking of an object. The Institutional Review Board at the University of Nebraska Medical Center reviewed and approved the protocol for this investigation, and all participants and their guardians provided informed assent and consent, respectively, to participate in the study.

Intervention

The participants attended a 2-week HABIT camp for 10 consecutive business days with 4 hours of treatment per day, with 2 hours of the camp being standard HABIT and 2 hours of the camp being HABIT-VR. The HABIT camp used a 1:1 ratio of the child to interventionist. The interventionists were physical therapy students, recreational therapists, and research assistants who were trained and supervised by licensed physical and occupational therapists. The interventionists guided and monitored each child's activities under the supervision of the physical and occupational therapists on-site. The children were split into 2 groups of 4, with 1 group participating in standard HABIT activities in a clinical space while the other group participated in HABIT-VR in a VR research laboratory. These groups switched rooms and activities approximately every 45 minutes.

The standard HABIT treatment followed treatment recommendations by Charles and Gordon2 and the procedures in the study by Surkar et al.4 When the children were participating in the standard HABIT activities, the participants were allowed to self-select preferred bimanual activities and were encouraged to also engage with nonpreferred activities. All the activities were bimanual gross or fine motor activities delivered in a play context and personalized to each participant's ability level. The intervention team selected bimanual activities that emphasized differing arm roles, for example, stabilizer, manipulator, and active/passive assisting. Throughout the camp, children were presented with tasks of increasing but appropriately scaled difficulty. To do this, the interventionists used whole- and part-task practice. Throughout the camp, the interventionists were encouraged to manipulate task parameters, such as task speed, the velocity of movements during the task, increasing cognitive difficulty as child task success increases, and the distance of movements. For all activities, the interventionist emphasized completing each movement with the more involved upper extremity to increase its use in bimanual activities. Interventionists were trained to provide positive feedback to ensure that children were receiving consistent knowledge of results and reinforce the movements during purposeful practice.4 After the HABIT session, we conducted a daily meeting to give feedback to the interventionists, discuss the child's progress, and therapy goals for the next session.

HABIT-VR

HABIT-VR (Figure 1) uses immersive 3D VR games based on HABIT treatment tasks. During the camp, 6 games were available for the children (Figure 2). All games were built using the Unity Game Engine and ran on the Oculus platform. The games ran on a VR compatible computer that was connected via USB to an Oculus Quest. Because the Quest system was connected via USB, the interventionists had access to a user interface that provided task-scaling options for each game. This user interface enabled the interventionists to change the parameters of the game based on the child's functional needs or adjust the challenge point. By modifying the motor or cognitive challenge point, the difficulty was individualized in each game. During the precamp assessment, all 8 participants demonstrated difficulty pressing controller buttons with their nondominant hand, so the “Touch Mode” was enabled by default.

F1
Fig. 1.:
A seated participant wearing an Oculus Quest VR headset playing the HABIT-VR software. The Quest device is attached to the computer via USB so that the treating professional can monitor the game and make adjustments to the game as needed. The player's view is displayed on the computer monitor, with the additional therapist user interface options visible only on the computer screen.
F2
Fig. 2.:
Screenshots from the 6 HABIT-VR games. (A) The player is tasked with firing rockets at robots. (B) The player opens jars in a factory. (C) The player serves ice cream in an ice cream truck. (D) The player collects stars by climbing through the environment. (E) The player makes potions by chopping up ingredients. (F) The player searches for treasure by diving to the ocean floor and swimming around the environment.

The participants were allowed to self-select preferred VR games to play; however, each day had a game chosen that the participants would be encouraged to focus on. Each game provided an in-game score to track progress and repetitions and provided immediate feedback on task completion. These scores established baseline performance and then each child was challenged to beat these scores during the camp. The participants were also given incentives to meet score values within certain time limits or number of attempts. These incentives were used to encourage long-term engagement. The score values and time limits were set relative to a baseline score and time set first thing each day of camp, individualized to each camper. The goals set encouraged the children to beat their previous score in a slightly shorter time window or try to earn a slightly higher score in the same amount of time. These individualized goals were set to make sure that the children were focusing on improving their own performance and were always being pushed to improve their movement speed and task performance. In addition, surprising and novel audiovisual feedback was provided within the game upon successful task completion.

Motor Function Testing

The children completed a pre- and post-training assessment that included the AHA, the BBT, and the 9-hole peg test (NHPT) to assess bimanual coordination, functional, gross, and fine motor skills, respectively. This battery of clinical assessments was chosen to mirror assessments commonly used to evaluate the effects of HABIT.3,4,13 The AHA is a tool to measure bimanual coordination and the affected hand function in children with unilateral CP, with a person reliability coefficient of 0.98.21 The BBT was administered as standard, with 2 trials per arm. The BBT is a tool to measure gross motor abilities in children with CP, with an intraclass correlation coefficient (ICC) of 0.98, a measurement error estimated by the MDC95 value of 5.95, and an interpretability estimated by the minimal clinically important difference ranging from 5.29 to 6.46.22 The NHPT was performed with a 50-second time limit, as defined by the Shirley Ryan Ability Lab.23 The NHPT is a tool to measure fine motor abilities in children with CP, with an intrarater reliability of ICC = 0.94 for the nonaffected side and ICC = 0.96 for the affected side.24

Data Analysis

A masked, certified coder scored the AHA data and had a 98.7% intrarater reliability score. The BBT and NHPT scores were reviewed on the basis of video recordings. The BBT and NHPT scorer had a 96.8% and 93.6% intrarater reliability score, respectively. Separate 2 × 2 mixed analyses of variance (pre-/post-HABIT-VR × dominant/nondominant arm) at an α level of 0.05 were used to determine whether there were significant differences in the BBT and the NHPT after HABIT-VR. A paired t tests assessed the pre- and post-HABIT-VR changes in the AHA. All statistical analyses were performed using R (R Foundation for Statistical Computing, Vienna, Austria).

RESULTS

Assisting Hand Assessment

There was a significant and clinically relevant improvement in AHA score (AHA score change of ≥5; Pre = 40.75 ± 11.4; Post = 51.5 ± 10.6, t7 = −5.033; P = .002, d = 0.97, Figure 3) after HABIT-VR.

F3
Fig. 3.:
Pre- and post-HABIT-VR assisting hand assessment scores. AHA Logits is on the y-axis and assessment block is denoted on the x-axis. White represents pre-HABIT-VR and black represents post-HABIT-VR. Error bars represent the standard error of the mean. The AHA scores increased after the HABIT-VR camp. AHA indicates Assisting Hand Assessment. *Significant difference at p < .05.

Box and Blocks Test

There was a significant pre–/post–main effect (Pre = 20.25 ± 10.1; Post = 23.03 ± 9.1 blocks, F1,7 = 15.721, P = .005, d = 0.26, Figure 4A), with a 13% increase in number of blocks moved during the BBT. There was a significant arm main effect (Dom = 20.25 ± 10.1; Non-Dom = 23.03 ± 9.1, F1,7 = 42.506, P < .001, Figure 4B), with the dominant arm moving more blocks than the nondominant arm. The interaction was not significant (F1,7 = 1.105; P = .3).

F4
Fig. 4.:
Box and blocks scores. The number of blocks moved is on the y-axis and assessment block is denoted on the x-axis. Error bars represent the standard error of the mean. (A) White represents pre-HABIT-VR and black represents post-HABIT-VR. The Box and Blocks Test (BBT) scores were higher after the HABIT-VR camp. (B) Light gray represents the dominant hand and dark gray represents the nondominant hand. The BBT scores were higher with the dominant hand. *Significant difference at p < .05.

Nine-Hole Peg Test

The pre–/post–main effect was not significant for the NHPT (Pre = 0.24 ± 0.27 pegs/s; Post = 0.25 ± 0.29 pegs/s, F1,7 = 1.235, P = .3, d = 0.05, Figure 5A). There was a significant arm main effect (Dom = 0.47 ± 0.22 pegs/s; Non-Dom = 0.02 ± 0.03 pegs/s, F1,7 = 30.589, P < .001, Figure 5B), with the dominant arm moving more pegs/s than the nondominant arm. The interaction was not significant (F1,7 = 2.032; P = .2).

F5
Fig. 5.:
Pre- and Post-HABIT-VR Nine-Hole Peg Test scores. The number of pegs per second is on the y-axis and assessment block is denoted on the x-axis. (A) White represents pre-HABIT-VR and black represents post-HABIT-VR. The NHPT scores did not change after the HABIT-VR camp. (B) Light gray represents the dominant hand and dark gray represents the nondominant hand. The NHPT scores were higher with the dominant hand. *Significant difference at p < .05.

DISCUSSION

This investigation evaluated the efficacy of using custom HABIT-style VR software as part of a HABIT treatment intervention camp. These results imply that a clinic-based HABIT treatment that uses HABIT-inspired therapeutic VR games as part of the treatment regimen may lead to bimanual coordination, functional, and upper extremity gross motor improvements.

Our results demonstrated improvements in bimanual coordination, functional, and gross motor skills. The increase in AHA scores was above the clinically relevant threshold (≥5 units), with 87.5% of the participants exceeding this threshold. In addition, the participants improved their unilateral gross motor skills, as measured by the BBT. These increases in AHA and BBT scores are consistent with other HABIT studies,3–5,13 suggesting that HABIT-VR did not detract from the camp's ability to drive improvements in upper extremity motor function. These data suggest that HABIT-VR has included the key therapeutic principles needed to contribute to upper extremity motor function improvements. Throughout the development of HABIT-VR, clinical experts provided their perspectives on the aspects needed to drive neuroplasticity and motor learning: a foundation based in evidence-based practice, configurability for individualized care, cognitive challenge, accessibility options, and independent motor and cognitive scaling. These principles were included in the design and fine-tuned through the iterative play testing, leading to an experience that balanced the child's enjoyment while maintaining the effectiveness of HABIT-VR as a therapeutic tool.

However, our participants did not increase their fine motor skills, demonstrating a specificity of results that suggests that the improvements seen in bimanual coordination and gross motor skills are not spurious outcomes. This was not a surprise, as task-specific fine motor skill practice is difficult in VR due to current technical limitations. The Oculus Quest comes with 2 controllers that have buttons like a traditional video game controller. The controller is designed to be held with the fourth and fifth fingers while the second and third fingers manipulate the buttons on the controller. The level of fine motor skill needed to hold the controller and manipulate the buttons can be difficult for children with CP.25 HABIT-VR was designed to require the use of only a single button, a trigger that is typically pressed with the third finger. During the preassessment, zero participants were able to press the required controller button with their affected hand and the games were put into “Touch Mode.” With all the games in “Touch Mode,” the amount of fine motor practice was minimized.

The inability to practice fine motor skills is a major limitation of providing HABIT-style treatment in VR. Technological advancements, such as hand tracking, electromyography (EMG) sensors, and VR gloves, could be used to help practice fine motor skills.26,27 However, the predictive algorithms behind camera-based hand tracking and EMG sensing systems are developed on the basis of biomechanical or physiological data collected from adults who developed typically. As individuals with CP have well-documented differences in their biomechanics and EMG responses,28,29 these technologies may not be optimal. However, VR gloves that are not predictive and rely on measurements of finger flexion and extension would enable VR experiences, including HABIT-VR, to be designed to work on fine motor skills.

Treatment Implications

These results are the first to support that HABIT-inspired software is feasible and could be used as part of a successful treatment regimen, which may provide a new avenue for HABIT-style therapy to continue beyond the clinic. There have been efforts behind trying to get HABIT-style therapy beyond the clinic by training caregivers or providing school-based camps.6,13 Although these models have shown success, they still require significant time and resources from the families or educational staff. HABIT-VR could address accessibility, time, and resource issues, making HABIT-style treatment available in home, rural, or school environments.

Future Directions

Further development of HABIT-VR aims to enable clinicians to perform remote monitoring of performance, add complex gaming mechanics to increase long-term motivation, and provide a platform for social interaction with peers. Remote monitoring would provide feedback on the child's performance and give the clinician the ability to change difficulty and accessibility options. These features would provide a way for clinicians to provide necessary scaling and coaching remotely, making continuous treatment more convenient for families and providers. Furthermore, HABIT-VR would provide a platform for continuing treatment after an in-clinic camp ends or a total camp experience for those who may not be able to attend in-clinic sessions. In addition, children who have access to HABIT-VR would have the opportunity for self-treatment. Serious games mechanics, such as player levels and narrative, can increase long-term engagement and promote intrinsic motivation.30 These features would be added to provide additional reasons to return to and increase their performance in the game. Finally, HABIT-VR could include features that would enable the children to interact with other players. Children with CP are more likely to be socially isolated than their typically developing peers, and this is often attributed to their ability to participate in the same activities.31 HABIT-VR could provide a platform of play that is accessible to people of all ability levels, providing a common ground and catalyst for social interaction.

Limitations

One limitation of this investigation is the lack of a comparison group. A more rigorous study aiming to demonstrate that HABIT-VR is a successful therapeutic software on its own would include a group for comparison against a completely standard HABIT session. However, this investigation aimed to evaluate the feasibility of running a camp augmented with immersive VR software and demonstrates that such software would enhance therapeutic outcomes. The results in the present study were also strengthened by having a masked professional score the AHA outcomes. Furthermore, due to our sample size, another limitation is the number of participants in each MACS level. Most of the participants had MACS levels of II and III. Because of this limitation, it is unclear whether these results would generalize to participants with higher MACS scores or assist those with MACS level I. Finally, while we can conclude that HABIT-VR did not reduce the effectiveness of this HABIT camp, with the small number of subjects, we cannot conclude that HABIT-VR was the sole reason for upper extremity functional improvements measured in this study. Future studies will need to evaluate the effect of HABIT-VR on its own to determine its therapeutic effect.

CONCLUSION

Our results support that children with unilateral or bilateral CP who participated in a HABIT camp with half the time spent using HABIT-inspired VR games increased in their bimanual coordination and function. Furthermore, the participants demonstrated improvements in their unilateral gross motor skills but not their fine motor skills. These results imply that VR games inspired by HABIT can be part of a treatment regimen to improve upper extremity function in children with unilateral CP.

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Keywords:

cerebral palsy; HABIT; intensive rehabilitation; virtual reality

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