INTRODUCTION
Stroke is a cerebrovascular disease that occurs when the blood supply to the brain is interrupted or when bleeding develops in brain tissue, resulting in loss of brain function [1]. It is a leading cause of both mortality and disability [2]. Most motor functions and physical abilities recover within six months after the onset of stroke [3,4], after which factors such as learning, practice, and confidence play a critical role in further recovery [3]. For this reason, the recovery of physical function during the early stage of stroke serves as an important indicator for predicting and determining patient prognosis [5,6]. In other words, because patients with central nervous system damage, such as stroke, can achieve a certain degree of recovery within a relatively short time through motor control and neuroplasticity mechanisms, active rehabilitation strategies are essential during the subacute phase [7-9].
Stroke patients typically bear approximately 70% of their body weight on the non-paretic side [10]. As a result, compared to healthy individuals, stroke patients typically exhibit asymmetric weight bearing and impaired weight shifting toward the paretic side, leading to increased postural sway in a static standing position [11]. Consequently, stability on the paretic side is reduced relative to the non-paretic side, which increases postural sway while standing and results in asymmetrical gait patterns [12,13]. Thus, the ideal goal in the functional rehabilitation of stroke patients is to reduce bodily asymmetry, promote equal weight bearing, and restore symmetrical gait ability while maintaining an upright standing posture [14]. Balance refers to the ability to maintain the body's center of gravity within the base of support while bearing weight and moving without falling. It is one of the most fundamental requirements for daily activities and social participation [15-17]. However, stroke patients often experience impaired balance [18], which can lead to gait disturbances, a critical factor in daily living [19]. Therefore, maintaining balance in an upright posture and improving gait ability are considered ultimate rehabilitation goals for patients with hemiplegia due to stroke [20].
In the standing posture, the feet serve as the supporting base for maintaining the body [21], and the diverse proprioceptive inputs received through the feet play a vital role in postural control [22,23]. Nevertheless, in stroke patients, secondary changes caused by neurological or non-neurological factors over time can decrease ankle and foot mobility, leading to deformities [24,25]. Accordingly, therapeutic interventions can be administered while correcting musculoskeletal problems of the ankle and foot in stroke patients through the use of a toe spreader.
Bobath [26] noted that the use of a toe spreader serves to separate the toes, thereby counteracting plantar flexion while maintaining them in an abducted position. This intervention not only alleviates stiffness in the foot and lower-limb extensors but also helps prevent deformities such as excessive plantar flexion and claw toe. In a study by De Saca et al. [27], stroke patients who performed gait training while wearing a toe spreader demonstrated increased walking speed and steps per minute. Similarly, in Lee et al. [28] study of chronic stroke patients, although plantar pressure did not show a significant difference, spatiotemporal gait parameters improved significantly with the toe spreader compared to without it. However, research examining plantar pressure as well as static and dynamic balance in stroke patients while wearing a toe spreader remains limited.
Therefore, this study compared plantar pressure and static/dynamic balance in stroke patients with and without the use of a toe spreader during standing posture— the stability stage of motor control theory— and during weight-shift adaptation training in standing posture— the controlled mobility stage. The objective of this study was to determine whether wearing a toe spreader affects plantar pressure and static/dynamic balance in stroke patients across these stages, thereby evaluating its potential clinical usefulness as an assistive device for therapeutic interventions aimed at improving plantar pressure and balance ability in stroke rehabilitation.
METHODS
1. Study Design
This study was conducted as a quasi-experimental investigation employing a crossover within-subjects design to examine differences in plantar pressure and balance in stroke patients with and without the application of a toe spreader. Specifically, We compared measurements of plantar pressure and balance under two conditions— wearing and not wearing a toe spreader— within the same group of participants.
A within-subjects design was employed to ensure that participants maintained identical anthropometrics across both conditions, thereby minimizing the influence of extraneous variables on the outcomes. To further control for order effects, the conditions were administered in a crossover sequence.
Thirty stroke patients were randomly allocated into two initial condition groups. In the first group (n=15), participants wore the toe spreader, performed standing and weight-shift adaptation training in the standing posture, and subsequently underwent plantar pressure and balance assessments. The second group (n=15) underwent the same procedures without the toe spreader. Following the assessment of each condition, participants were given a 10-min rest period before transitioning to the alternate condition, ∼ manner.
A flowchart summarizing the study design and procedures is presented in Fig. 1.
2. Participants
The required sample size was calculated using the G*Power 3.1 program. Based on a two-tailed test comparing the mean differences in paired conditions (toe spreader vs. no toe spreader) with a significance level (alpha error probability) of 0.05, statistical power of 80%, and an effect size of 0.5, the required number of participants was determined to be 27. To account for potential dropouts, 30 patients were recruited through a public notice. Eligible participants were medically diagnosed with stroke by specialists in rehabilitation medicine or neurology/neurosurgery and were receiving treatment at D Medical Center in Busan. All participants were given a detailed explanation of the study's objectives and experimental procedures, after which written informed consent was obtained. Participants were informed that they could withdraw from the study at any time without penalty or consequence.
Inclusion criteria were as follows: Patients in the subacute phase within approximately 1 to 6 months after stroke onset; a score of ≥24 on the Korean version of the Mini-Mental State Examination (MMSE-K); muscle strength of the paretic lower limb graded as fair or higher on Manual Muscle Testing (MMT); ability to maintain an independent standing posture for at least 10 minutes; absence of open wounds or deformities of the feet or toes; and no history of orthopedic disorders or surgery involving the feet.
Exclusion criteria were as follows: prior experience with a toe spreader; pain or abnormal symptoms during toe spreader use; visual or auditory impairments; and Use of pharmacological agents (e.g., muscle relaxants) for spasticity management in the paretic muscles.
Prior to the commencement of the study, approval was obtained from the Institutional Review Board (IRB) of Dong-Eui University to ensure compliance with laws and regulations regarding bioethics and safety, and to safeguard the rights, safety, and well-being of participants (IRB No. DIRB-202110-HR-E-25).
3. Toe Spreader Adaptation Training Program
The toe spreader (Samderson Medical Corp., Taipei, Taiwan) employed in this study is a simple corrective device positioned between the toes (Fig. 2). When placed beneath the toes, it functions to separate them evenly, thereby promoting a more symmetrical distribution of body weight during standing. Representative illustrations of the foot without the device, with the device in place, and immediately following application after adaptation training are shown in Fig. 3.
Fig. 3.
Fig. 3.(A) Barefoot, (B) Wearing toe spreader, (C) After wearing (After adaptation training).
The participants in this study were subacute stroke patients unable to walk independently but capable of maintaining an upright standing posture. Based on their clinical characteristics, an adaptation training program was implemented according to the stability and controlled mobility stages of the four-stage motor control model proposed by Stockmeyer [16]. Detailed components of the adaptation training program are provided in Table 1.
Table 1.
Standing position and weight shift adaption training program in a standing position
4. Plantar Pressure Measurement
Plantar pressure was measured using the Zebris (FDM-S, Zebris Medical GmbH, Isny, Germany). This instrument has demonstrated high reliability, with an intraclass correlation coefficient (ICC) of 0.86 for plantar pressure measurement [29]. Participants stood barefoot with both feet placed parallel on the platform, maintaining an upright posture while keeping their eyes open and looking straight ahead. They were instructed to stabilize themselves, after which plantar pressure was measured on the paretic foot for 10 seconds. Each participant underwent three repeated measurements, and the mean value was calculated.
5. Static and Dynamic Balance Measurement
Static and dynamic balance were assessed using BioRescue (RM Ingenierie, Rodez, France), a motion analysis system with a pressure-sensitive platform. This device is capable of evaluating and training weight-bearing symmetry and balance ability across a wide range of populations, including those with central nervous system impairments [30]. Prior to measurement, participants were given a detailed explanation of the procedures for static and dynamic balance assessment. The researcher demonstrated the methods directly using a monitor to ensure understanding. As with plantar pressure, three repeated trials were conducted for each balance measurement, and the average values were used for analysis. For static balance, participants stood upright on the pressure-sensitive platform with their feet positioned approximately 30° apart, eyes open, and looking forward. While maintaining balance for 15 seconds, the total surface area and path length of the center of pressure were re-corded (Fig. 4). For dynamic balance, participants stood on the pressure-sensitive platform with their fingers interlaced and performed three forward arm raises with their shoulders flexed to 90°. They then performed three arm raises at 90° shoulder flexion while rotating the trunk toward 45° diagonal directions on both the left and right sides. To ensure accuracy in arm movement direction and angle, reference points were marked at eye level directly in front of the platform, as well as at 45° diagonals to the left and right (Fig. 5).
6. Data Analysis
The data collected in this study were analyzed using SPSS 26.0 for Windows (IBM Corp., Armonk, NY, USA) program. Descriptive statistics were calculated for the general characteristics of the participants. The normality of the measured variables was verified through the Kolmogorov-Smirnov test, after which parametric tests were performed. Differences in plantar pressure and static/dynamic balance between the toe spreader and non-toe spreader conditions in stroke patients were analyzed using a paired t-test. The statistical significance level (α) was set to .05.
RESULTS
1. General Characteristics of Participants
The detailed general characteristics of the 30 participants are shown in Table 2.
Table 2.
General characteristics of subjects (n=30)
| Variable | Value | |
|---|---|---|
| Gender | Male | 17 (56.70%) |
| Female | 13 (43.30%) | |
| Lesion cause | Hemorrhage | 7 (23.30%) |
| Infarction | 23 (76.70%) | |
| Affected side | Right | 14 (46.70%) |
| Left | 16 (53.30%) | |
| Age (years) | 61.40±4.61† | |
| Height (cm) | 166.76±6.79† | |
| Weight (kg) | 65.67±6.68† | |
| Time since stroke (week) | 13.30±4.84† |
2. Plantar Pressure
After standing posture adaptation training, the mean plantar pressure increased by 9.32% with the toe spreader compared to without, showing a statistically significant difference. Similarly, after weight-shift adaptation training in the standing position, the mean plantar pressure increased by 9.17% with the toe spreader compared to without, also demonstrating a statistically significant difference (Table 3).
3. Static Balance
Following standing posture adaptation training, static balance results indicated that the mean surface area decreased by 36.62 mm2 and the mean path length decreased by 3.18 cm when using the toe spreader compared to not using it. Both the total surface area and path length of the center of pressure were reduced, showing statistically significant differences. Likewise, after weight-shift adaptation training in the standing position, the mean surface area decreased by 52.14 mm2, and the mean path length decreased by 4.09 cm with the toe spreader compared to without, with both measures showing statistically significant reductions (Table 4).
Table 4.
Static balance
4. Dynamic Balance
After standing posture adaptation training, dynamic balance results showed that the mean surface area decreased by 236.62 mm2 and the mean path length decreased by 11.12 cm when using the toe spreader compared to not using it. Both measures of the center of pressure were reduced, indicating statistically significant differences. Furthermore, after weight-shift adaptation training in the standing position, the mean surface area decreased by 260.55 mm2, and the mean path length decreased by 11.34 cm with the toe spreader compared to without, both demonstrating statistically significant reductions (Table 5).
Table 5.
Dynamic balance
DISCUSSION
This study was conducted to examine the effects of wearing a toe spreader on plantar pressure and balance in stroke patients during standing posture (the stability stage of the motor control model) and during weight-shift adaptation training in standing posture (the controlled mobility stage). Although precise comparisons with previous studies are limited due to variations in participant characteristics, clinical symptoms, physical functions, study duration, and methodology, the discussion focuses primarily on similarities in research methods and measurement outcomes.
Stroke patients exhibit mechanical, asymmetrical gait, with compensatory adjustments through control of the non-paretic lower, further amplifying asymmetry. Such weight-bearing asymmetry, with plantar pressure concentrated on the non-paretic side, significantly affects over-all body movement [31]. Accordingly, one of the therapeutic goals for hemiplegic patients is to enhance weight-shifting ability toward the paretic side. Chiong et al. [32] conducted a six-month randomized controlled pilot study on poststroke patients with overactive toe flexors. They found that the group wearing a toe spreader maintained plantar contact surface area, whereas the non-wearing group showed a reduction. The toe spreader functions by positioning the metatarsophalangeal joints in a neutral or slightly extended upward alignment, thereby pre-venting excessive flexion of the interphalangeal joints [33].
Consistent with these findings, the present study demonstrated that in stroke patients, wearing a toe spreader led to a statistically significant increase in plantar pressure on the paretic side during both standing posture and weight-shift adaptation training. This effect is likely attributable to the toe spreader's facilitation of sufficient plantar contact with the ground, which promotes normal sensory input from both cutaneous and proprioceptive receptors, reduces pain and discomfort caused by excessive foot tension or toe flexion, and enables smoother weight shifting on the support surface.
Lee et al. [28], in a study involving chronic stroke patients, reported a slight increase in plantar pressure and rearfoot pressure on the paretic side when wearing a toe spreader, though the difference was not statistically significant compared to the non-wearing condition. In contrast, the present study found a statistically significant increase in plantar pressure on the paretic side when using the toe spreader compared to not using it. This discrepancy may be explained by the fact that previous research measured plantar pressure immediately after donning the toe spreader without adaptation training. In contrast, in this study, plantar pressure was measured after participants underwent a 10-minute session of standing posture and weight-shift adaptation training while wearing the device.
Goliwas et al. [34] reported that stimulation of the foot in stroke patients induced increased weight bearing on the paretic side and reduced asymmetry in weight distribution between the paretic and non-paretic sides while standing. Similarly, Vaillant et al. [35] found that therapeutic interventions targeting the ankle and foot improved postural control during standing, noting that patients were able to achieve postural control benefits while remaining still. These effects were attributed to increased foot-ground contact achieved through training that stimulated the ankle and foot, as well as enhanced muscle activation in the paretic leg during balance training, which contributed to improved balance ability.
In the present study, the use of a toe spreader provided a novel form of stimulation for stroke patients by counteracting the commonly observed toe flexion, encouraging toe extension, and widening the toe spacing. As a result, this expanded the plantar contact surface, provided a greater sense of stability, and enabled the entire sole to make contact with the support surface. Combined with repeated weight-shift training in the standing posture— corresponding to the stability and controlled mobility stages of the motor control theory— this intervention resulted in improvements in static balance ability, particularly the ability to maintain the center of gravity while standing.
Anatomically, the foot is the only body part in direct contact with the ground during standing and walking, making it a crucial component in the performance of functional, such as gait [36]. However, structural changes in the foot following a stroke often result in functional impairments that negatively affect limb movement and balance control [37]. Consequently, a range of non-surgical approaches, including clinical use of various foot orthoses, have been applied to prevent deformities and malalignment of the foot and ankle while promoting correct biomechanical alignment. Numerous studies have been conducted to enhance foot function through such interventions [28,38,39].
Wearing an ankle-foot orthosis (AFO) compensates for ankle joint instability, enhances stability during standing, and allows partial mobility of the body [40]. According to Wang et al. [41], dynamic balance control in hemiplegic patients significantly improved when they wore an AFO. In line with these findings, the present study demonstrated that the use of a toe spreader in stroke patients increased plantar contact surface, thereby enhancing ankle stability and sensory input. Under these conditions, repetitive weight-shift adaptation training in standing posture led to improvements in dynamic balance, consistent with previous research.
De Saca et al. [27] reported that the application of a toe spreader in patients with hemiplegia increased both walking speed and cadence. Similarly, Lee et al. [28] found significant differences in spatiotemporal gait parameters between wearing and not wearing a toe spreader in chronic stroke patients. In contrast, the present study could not directly compare gait parameters, as the participants were subacute stroke patients unable to walk independently, despite using the same measurement device (toe spreader). Instead, findings revealed that wearing the toe spreader during standing posture and weight-shift training decreased weight-bearing on the non-paretic side and increased weight-bearing on the paretic side in subacute stroke patients unable to walk independently. Therefore, the application of toe spreader facilitates increased weight-bearing on the paretic side, resulting in improved ground reaction force generation and subsequent enhancement of gait parameters in hemiplegic patients.
Several studies have reported that standing balance in stroke patients is significantly correlated with gait ability [42,43]. Similarly, the present study found that the Use of a toe spreader, combined with stability-focused adaptation training through equal Weight-bearing and controlled mobility training. That promotes weight shifting to the paretic side, enhanced body symmetry and improved both static and dynamic balance abilities. Accordingly, depending on the degree of recovery, appropriate application of a toe spreader in stroke patients could be clinically utilized to improve functional movements, including gait, and to support rehabilitation.
However, this study did not assess the long-term effects of wearing a toe spreader following an intervention program applied over a sustained period. Additionally, the inclusion criteria were limited to subacute stroke patients within six months of onset who exhibited only mild balance impairments and were able to maintain standing posture for more than 10 minutes. As such, the study was unable to verify the effects of a gait intervention program for chronic stroke patients. Future research should build upon these findings by conducting systematic measurements and experimental studies that investigate the effects of toe spreader use and related intervention programs across a broader range of central nervous system disorders, varying degrees of disability, and different recovery periods.
CONCLUSION
The findings of this study demonstrated that the Use of a toe spreader in stroke patients significantly increased plantar pressure on the affected side, while both the surface area and path length of the center of pressure during static and dynamic balance were significantly reduced. These results suggest that the toe spreader contributes to correcting asymmetric weight-bearing and improving balance control by providing a more stable base of support.
Moreover, the enhanced capacity for weight shifting and balance regulation may improve the mechanical efficiency of gait, attenuate asymmetry and instability during walking, and augment the load-transfer and postural-maintenance functions required for activities of daily living (ADL).
Taken together, these findings indicate that the toe spreader may serve as an effective therapeutic intervention that simultaneously facilitates improvements in both gait function and ADL performance in individuals with stroke.
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