Effects of Virtual Reality-Combined Treadmill Gait Training on Balance and Walking in Children with Spastic Cerebral Palsy

1. Introduction

Cerebral palsy is caused by non-progressive damage to the brain of a fetus or infant, leading to disorders in movement and posture, resulting in activity limitations. It is often accompanied by sensory, cognitive, communicative, perceptual, and behavioral disorders and seizures [1]. Children with cerebral palsy exhibit abnormal muscle tone and reflexes, abnormal central postural control mechanisms, and impaired integration of sensory-motor information, resulting in rigidity, physical asymmetry and tremors, and joint deformities [2].

In particular, the ability to maintain the center of gravity over the base of support in the trunk and both legs decreases, making it difficult to shift weight, which is necessary for maintaining a symmetrical posture [3]. This problem diminishes posture control abilities during activities such as sitting, standing, and walking, leading to severe functional impairments in daily activities [4]. Regardless of the extent of brain damage, almost all children with cerebral palsy experience significant impairments in gross motor function, limiting social interactions and reducing the quality of life [5]. Additionally, balance issues are common problems in children with cerebral palsy [6]. Due to their highly unstable limb control and posture regulation abilities [7], children with cerebral palsy exhibit abnormal stereotyped patterns in standing and walking, which arise from abnormal reflexes, abnormal muscle tone, physical asymmetry, abnormal tremors, and balance disorders [8].

Current clinical treatments for cerebral palsy include Bobath therapy, Vojta therapy, and Proprioceptive Neuromuscular Facilitation (PNF). These therapies primarily focus on addressing muscle tone, abnormal reflexes, and atypical movement patterns. However, these traditional treatments often face challenges, such as being limited to hospital settings and lacking the ability to sustain a child’s interest and motivation in therapy [9,10]. Recently, various intervention methods have been applied to address the structural problems of children with cerebral palsy, but interventions related to walking remain insufficient. Previous studies on walking-related intervention methods are as follows. Among the children with cerebral palsy who are capable of walking, many require absolute caregiver assistance or exhibit abnormal and limited walking patterns due to muscle weakness, rigidity, sensory impairments, and difficulty in maintaining balance [11]. Thus, enabling these children to walk and make normal gait as much as possible is a crucial goal of rehabilitation therapy. For this purpose, various rehabilitation methods, such as managing spasticity, applying neurodevelopmental techniques, and strength training exercises, are used, though the outcomes are not always satisfactory. Therefore, new approaches have been discussed recently, in addition to the universally practiced traditional methods. One such technique involves using a partial body-weight support device in a dynamic state to facilitate weight unloading, followed by treadmill gait training [11,12,13].

In clinical settings, the repetitive nature of treadmill gait training needs to be improved to engage patients, and the lack of accurate movement analysis and feedback can lead to accumulated errors and reduced training effectiveness [14]. Recently, to enhance interest and participation in treating patients with neurological damage, rehabilitation exercise methods involving virtual reality, which incorporate a variety of tasks performed in a virtual environment, have been introduced [15,16]. Virtual reality rehabilitation programs can be safely applied to patients who cannot adapt to the real environment due to motor and cognitive impairments resulting from brain injuries [17]. Moreover, by moving and manipulating objects to complete tasks, patients exhibit realistic responses through virtual efforts [18]. Since the late 1990s, virtual reality has been applied to a wide range of patients in the rehabilitation sector, enhancing their functions [19]. This approach is characterized by incorporating sensory integration aspects of traditional interventions aimed at promoting neurodevelopment and inhibiting abnormal reflexes while also including recent additions such as strength training and aerobic exercises into its therapeutic goals. It is expected that a positive rehabilitation effect will be achieved by increasing the interest and motivation of children with cerebral palsy during their rehabilitation.

Additionally, virtual reality-based activities are interactive, stimulating sufficient motivation and interest and creating a safe environment, making them an attractive option for cerebral palsy children’s intervention programs [16]. While research on the effects of virtual reality-based exercise program interventions has been actively con-ducted with stroke patients [20,21,22,23] studies aimed at observing the effects on balance and walking in children with cerebral palsy are either single-case studies [24], have single experimental group designs [25], or focus on hand-eye coordination [26], and thus are somewhat limited. Against this backdrop, this study aims to investigate the changes in balance and walking by applying virtual reality combined treadmill gait training to children with spastic cerebral palsy and to inform clinicians of the effectiveness of the virtual reality combined treadmill gait training program and enhance the efficiency of therapeutic interventions for children with cerebral palsy in the community.

2. Materials and Methods

2.1. Participations

This study was conducted on 30 children with spastic cerebral palsy who visited the outpatient rehabilitation departments at Hospitals B and C in Gyeonggi Province following IRB approval, with parental consent for participation. Children with spastic cerebral palsy who also had intellectual disabilities, as indicated in their medical records, were excluded from the study. The participants were randomly assigned to two groups: one group underwent virtual reality treadmill gait training, and the other group received traditional strength training in physical therapy, with each group comprising 15 children. The eligibility criteria for participants were as follows: (1) children medically diagnosed with spastic cerebral palsy at Levels I or II of the Gross Motor Function Classification System (GMFCS), (2) children able to understand instructions and cooperate with the researchers, (3) children without any recorded visual or auditory impairments, and (4) children not on any medication affecting balance, without ear surgeries, and free of dizziness.

2.2. Design

This study was a randomized controlled trial. Participants were randomly assigned to either the experimental group (n=15) or the control group (n=15) by drawing a piece of paper labeled with the number 1 or 2. Figure 1

2.3. Procedure

To select the number of subjects in this study, the G-Power Ver. 3.1 was used on the results of previous research. The allocation ratio of the two groups was 1:1; the alpha level was set to .05; the power was set to .95; the magnitude of the effect was determined to be .881. As a result, the total sample size was 30, so 30 participants were selected for the study. After drawing a piece of paper with the number 1 or 2 from a basket, the subjects were randomly divided into two groups. In line with the experimental methods, fifteen individuals were randomly assigned to (1) a Virtual Reality Combined Treadmill Gait Training (VTG) group, and (2) a general physiotherapy group (CON). The virtual reality combined treadmill gait training group and the conservative treatment group underwent their respective training sessions three times a week for 4 weeks, each lasting 30 minutes. Before and after the training period, ankle joint muscle tone, joint angles, and balance were assessed. In the virtual reality combined treadmill gait training group, participants wore virtual reality devices (Oculus, Samsung, Korea) and performed treadmill walking for 30 minutes. The conservative treatment group performed strength exercises in two 15-minute sets, similar to the virtual reality treadmill training group, resulting in 30 minutes of exercise. This study was conducted after receiving the approval of the Institutional Bioethics Committee of Gimcheon University. (Approval number GU-202409-HRa-20-P)

2.3.1. Virtual Reality Combined Treadmill Gait Training (VTG) Group

Virtual reality training was set up with two sessions: a 15-minute stroll through a tourist site and a 15-minute urban walk pre-recorded in 3D. Time was allotted before the intervention for participants to adapt to the Oculus device, ensuring no issues during the session. The immersive virtual reality device provided an engaging environment through visual and audio outputs from the headset worn by the participants. Participants wore virtual reality equipment and conducted treadmill walking training. During these sessions, an assistant physical therapist positioned themselves directly behind the participant to prevent falls and other safety measures. The session was immediately stopped if the participant could not continue the training for 15 minutes due to their physical capability. Furthermore, if the participant experienced fatigue, pain, breathing difficulties, or changes in complexion during training, a five-minute rest period was permitted [27]. Figure 2

2.3.2. Conservative Treatment (CON) Group

The CON involved strength training aimed at activating and enhancing posture-related muscles. The CON involved strength training aimed at activating and enhancing posture-related muscles. This included exercises for seven leg muscle groups: hip flexors, extensor muscles, abductors, knee flexors, knee abductors, and ankle dorsiflex-ion [28]. Each exercise was performed in two sets of ten repetitions. The exercise regimen included the following: (1) lifting the torso to strengthen the trunk and hip joints, (2) prone trunk lifts on a ball, (3) bending and straightening the knees while seated on a therapeutic bench, (4) standing from a kneeling position with support, (5) standing on one leg with hand support against a wall.

2.4. Evaluation

2.4.1. Gross Motor Function Classification System (GMFCS)

The GMFCS is used to assess the level of functional limitation in children with cerebral palsy, classifying them into five age groups (under two years, 2-4 years, 4-6 years, 6-12 years, and 13-18 years) and further into five levels of severity within each age group. This study focused on children at Levels I and II, where Level I includes children who can walk without difficulty but struggle with more complex gross motor functions. Level II consists of those who can walk unaided but find it challenging to walk outside [29]. The inter-rater reliability of the GMFCS is 0.96, and the test-retest reliability is 0.79 [30].

2.4.2. Balance Test

Balance was measured using a balance measurement system (Biorescue, Marseille, France). The Center of Pres-sure (COP) was assessed by participants standing with their legs about 30 degrees apart, facing forward. After a demonstration by the tester, participants maintained a standing position for one minute, during which the total movement of the COP was recorded. The Limits of Stability (LOS) were measured using the device software, which calculated the total area moved by the COP in forward-backward, left-right, and diagonal directions. The feet remained on the floor during testing, and if they were lifted, measurements were retaken. In this study, the COP is used to measure balance ability in a standing posture. The measurement of the COP represents the average force at the pressure points in contact with the ground, reflecting changes at the point where ground reaction forces are synthesized [31].

2.4.3. Gait Analysis

The G-walk (BTS Bioengineering SpA) system was utilized to analyze walking ability. This system, employing a wireless tri-axial accelerometer, measures the subject’s Center of Mass (COM). The accelerometer is attached at the level of the fifth lumbar vertebra using Velcro. During the test, the participant walked to gather spatiotemporal variables such as walking speed, step length, and cadence. These parameters were wirelessly transmitted for analysis to the BTS G-studio Software (version 2.8.16.0) via Bluetooth [32]. It has been reported that this lower back-mounted accelerometer can detect walking imbalances in patients [33]. This study took Each measure three times to calculate an average value. The reliability of the tester’s measurements was r=0.90 [34].

2.5. Data Analysis

The SPSS Win. 21.0 Package was used to analyze collected data in this study. Descriptive statistics (mean and standard deviation) were calculated, and the homogeneity of dependent variables before training was tested using an independent sample test. Comparisons within groups before and after the intervention were conducted using paired comparison tests and between groups using independent sample tests. Furthermore, measuring the change before and after training determined the intervention’s effect size. All statistical significance levels were set at α=.05.

3. Results

3.1. General and Clinical Characteristics of the Patients

This study involved 30 participants: 15 in the VTG group and 15 in the CON group. There were no significant differences between the groups regarding gender, age, height, weight, GMFCS levels, and types of paralysis (Table 1).

3.2. Changes in Balance Ability Before and After Intervention

Both groups showed significant differences in balance ability before and after training. When comparing the changes in balance ability (COP, LOS) between the two groups, the VTG group showed a significant improvement over the CON group (p<.05) (Table 2).

3.3. Changes in Walking Ability Before and After Intervention

Both groups exhibited significant differences in walking ability before and after training. Comparisons of changes in walking ability (Velocity, Step length, Cadence) between the two groups revealed that the VTG group showed a significantly more significant improvement than the CON group (p<.05) (Table 3).

4. Discussion

Among the various approaches to treating children with cerebral palsy, virtual reality exercise programs allow patients to enjoy tasks and increase motivation for therapy [35]. Patients can train and learn autonomously, checking their task performance results, thus allowing for tailored virtual environments suitable for individual recovery progress or severity of disability [16]. Cerebral palsy children’s brain plasticity and behavioral changes improve when treated with methods requiring task performance and problem-solving skills [36].

Additionally, treadmill walking training has been reported as an effective exercise program that enhances life quality and promotes physiologically correct walking patterns in children with cerebral palsy [37]. Against this backdrop, this study aimed to investigate the impact of VTG on balance and walking in children with spastic cerebral palsy. The results of this study indicate that balance abilities improved in the VTG compared to the control group. Specifically, the COP values in the VTG decreased from 12.98 cm before the intervention to 10.56 cm after, a reduction of 2.42 cm. The LOS increased from 5599.43 cm² pre-intervention to 7635.41 cm² post-intervention, an increase of 2035.97 cm². This aligns with previous studies reporting increased functional balance abilities following virtual reality exercise programs in children with spastic cerebral palsy [15].

This improvement is believed to stem from applying a virtual reality exercise program to treadmill walking training, which provided varied visual and auditory stimuli to children with cerebral palsy. The program enabled the integration and regulation of balance-related spatial, vestibular, and proprioceptive senses. Consequently, this practice enhanced balance abilities, stability recovery, and improved control skills. Although not all studies used the same balance assessment tools, various functional assessment tools reported improved physical control and balance in participants after virtual reality interventions, supporting the findings of this study. The findings of this study suggest that the virtual reality exercise program applied to children with cerebral palsy effectively enhances attention for goal achievement, thereby motivating active participation in therapy. Virtual reality creates a training environment that provides intense practice and positive feedback, thus improving performance capabilities [15].

By simulating environments similar to everyday activities, such as walking in daily life, through virtual reality equipment, this study allowed children with cerebral palsy to experience walking in an outdoor environment. This experience actively engaged them in the study’s intervention, fostering a sense of accomplishment and improved concentration. It allowed them to experience various walking patterns and enhance their motor function and balance control abilities. The results of this study indicate significant differences in balance ability between VTG and the control group (P<.05). This suggests that VTG is significantly more effective in improving the balance abilities of children with spastic cerebral palsy compared to CON. This can provide foundational data for planning exercise programs aimed at improving balance in children with spastic cerebral palsy. Applying VTG to children with spas-tic cerebral palsy provides appropriate visual feedback that stimulates brain activity [38]. Additionally, a study by Deutsch et al. in 2008 reported that after 11 sessions of virtual training programs lasting between 60 and 90 minutes, there was an improvement in balance control. The virtual environment programs offer the advantage of stimulating integrated sensory experiences through varied visual stimuli that affect the vestibular and somatosensory systems, closely related to balance [39]. The virtual reality program used in this study provided stimuli affecting visual and auditory feedback during balance control. These stimuli, integrated with inputs from the vestibular system and proprioceptors, are believed to influence balance control [40]. The results on walking ability showed significant differences between the VTG group and the CON group in terms of velocity, step length, and cadence after the intervention (P<.05). The increased walking speed can be attributed to the effects of VTG, which enhanced leg muscle strength and balance ability, thus improving dynamic postural stability and walking capability. Generally, walking requires about 38% of the VO2 max for aerobic capacity related to walking endurance, and muscle performance consists of strength, endurance, and power. Additionally, improved balance ability is crucial in enhancing walking ability [41].

Thus, the study concludes that balance improvement following the VTG has enhanced the walking ability of children with spastic cerebral palsy. Previous studies indicate that skills learned in virtual reality walking training effectively transfer to real-world walking environments, significantly improving walking activities [41], consistent with the results of this study.

A 2005 study by Harris & Reid [42] reported that virtual reality exercise programs could appropriately motivate children with cerebral palsy and facilitate rehabilitation training. Moreover, Burdea et al [14] reported significant increases in ankle dorsiflexion and plantar flexion strength in children with cerebral palsy after three weekly virtual reality-based exercise program sessions.

While it is challenging to make precise comparisons due to the current lack of studies using virtual or augmented reality in children with cerebral palsy, providing visual feedback of their movements has stimulated the motor units of the ankle joint, leading to increased Velocity, Step Length, and Cadence. Prolonged rehabilitation training requires patient engagement, and the training method should not be tedious or difficult but instead engaging [43]. The virtual reality combined gait training program applied in this study allows therapists to participate directly or indirectly in the virtual space, facilitating appropriate difficulty adjustment and encouraging active patient participation. Additionally, the virtual training environment can detect and update the patient’s body movements, providing alignment between visual and proprioceptive sensory information during training [44]. In virtual rehabilitation, stimuli and the virtual environment provide essential feedback for performing exercises and facilitate adapting challenging tasks, allowing individuals to accomplish these tasks according to their abilities. Moreover, the virtual environment stimulates the motor areas of the brain, providing motor learning for specific movements [45], and has also been reported to reorganize the sensorimotor areas in patients with neurological disorders like cerebral palsy [46].

In summary, the results of this study suggest several beneficial effects of the VTG on the balance and walking abilities of children with cerebral palsy.

The primary evaluation variable indicates that the VTG has a therapeutic effect on balance abilities post-training. A secondary evaluation variable is that the VTG is highly effective in enhancing the walking abilities of children with spastic cerebral palsy. The limitations of this study include the relatively short intervention period of 4 weeks and the lack of follow-up evaluations, which means the results cannot necessarily be generalized to potential long-term treatment effects. Additionally, since the study was conducted on children with spastic cerebral palsy, the findings are specific to this subgroup and may not apply to children with other types of cerebral palsy.

Future research should include a larger sample size, and, notably, this study only involved children with spastic cerebral palsy. Therefore, future studies should apply VTG to various types of cerebral palsy, including ataxia and athetosis. The findings of this study can serve as foundational data for physical therapists in clinical settings to plan more efficient exercise programs for patients with spastic cerebral palsy.

5. Conclusions

This study aimed to investigate the effects of the VTG on the balance and walking abilities of children with spastic cerebral palsy. This study involved 30 children with spastic cerebral palsy, with 15 in the experimental group receiving VTG over 4 weeks and 15 in the control group receiving CON. The experimental group showed a significant increase in COP and LOS values compared to the control group. Based on the results of this study, virtual reality treadmill gait training significantly contributed to improving the balance ability of children with cerebral palsy. This suggests that virtual reality treadmill gait training is a positive intervention for children with spastic cerebral palsy who have reduced balance ability. It provides foundational data for developing balanced programs for these children in clinical settings. Regarding walking, the experimental group showed significant increases in velocity, step length, and cadence post-intervention compared to pre-intervention scores, with differences significantly higher than those of the control group. Thus, the application of VTG over 4 weeks has proven helpful in improving the balance and walking abilities of children with spastic cerebral palsy. Currently, virtual reality exercise programs have not become widespread among children with cerebral palsy, and research in this area, especially concerning children rather than adults, still needs to be done. Moving forward, further research could significantly enhance the development of virtual reality exercise programs, potentially aiding in rehabilitating children with cerebral palsy.