https://orcid.org/0000-0001-7809-7496
Figures
Abstract
Background
Stroke frequently leads to motor impairments, with almost half of the affected individuals experiencing diminished sensation, impacting their overall quality of life and autonomy. Rehabilitation efforts, however, often overlook somatosensory functions of the lower limbs. While plantar sensory stimulation activates receptors in the foot sole, its precise impact on the motor functions and gait of individuals with stroke is yet to be ascertained.
Objectives
This systematic review and meta-analysis aimed to examine the effects of sensory interventions on gait and lower limb motor function in individuals with stroke.
Methods
We searched eight databases from inception to December 2023 for randomized controlled trials that investigated sensory interventions targeting gait or lower limb motor function in stroke patients. The primary outcomes included changes in gait and motor function, reported as standardized mean differences (SMD) and assessed heterogeneity (I2).
Results
A total of [number] studies were included, covering different sensory modalities such as textured insoles, plantar vibration, and cognitive sensorimotor exercises. The interventions showed varying effectiveness, with plantar vibration therapy exhibiting a large effect size (SMD = 2.03 [1.13, 2.94]) for improving lower limb motor function, while textured insoles showed moderate effectiveness (SMD = 0.58 [0.24, 0.92]) with no heterogeneity (I2 = 0%). For gait, significant enhancement was seen with plantar vibration (SMD = 3.17 [2.05, 4.29]) and cognitive sensorimotor training (SMD = 2.85 [1.69, 4.02]). However, overall heterogeneity was moderate to high (I2 = 65% for motor function, 85% for gait), indicating variability across different studies and intervention types.
Conclusion
The findings of this review and meta-analysis suggest that plantar somatosensory stimulation has the potential to improve lower limb motor function and gait in people with stroke. However, to firmly establish its efficacy as a rehabilitative tool, larger-scale and high-quality studies are requisite.
Citation: Ahmad AA, Suriyaamarit D, Siriphorn A (2024) Plantar sensory stimulation and its impact on gait and lower limb motor function in individuals with stroke: A systematic review and meta-analysis. PLoS ONE 19(12): e0315097. https://doi.org/10.1371/journal.pone.0315097
Editor: Monika Błaszczyszyn, Opole University of Technology: Politechnika Opolska, POLAND
Received: January 8, 2024; Accepted: November 20, 2024; Published: December 6, 2024
Copyright: © 2024 Ahmad et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: This research project received financial support from the Ratchadapiseksompotch Fund of Chulalongkorn University. The funders had no role in the design of the study, the collection and analysis of data, the decision to publish, or in the preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Stroke stands as a leading cause of severe and enduring disability, imposing significant healthcare expenditures and projecting future health economic burdens [1]. The risk of stroke escalates, particularly among individuals aged above 65 years, underscoring the pressing need for effective rehabilitation strategies to mitigate its impact on an aging population [2]. The ability to walk represents a fundamental marker of functional independence and engagement in social activities for stroke patients [3, 4]. However, following hospital discharge, a substantial proportion of stroke survivors—approximately 45%—encounter challenges in walking, characterized by an inability to ambulate or the manifestation of abnormal gait patterns with spatial and temporal asymmetries. This gait disability significantly impairs daily living activities, diminishes the overall quality of life, and may lead to secondary complications such as muscle shortening and joint impairments [5]. Consequently, timely and effective rehabilitation management is essential to enhance the quality of life for stroke patients. Even six months after experiencing a stroke, about 30% of survivors still require varying degrees of walking assistance, emphasizing the necessity for comprehensive and individualized interventions [6, 7].
Despite significant progress in identifying and treating post-stroke disability, the existing evidence is derived from heterogeneous studies, making it challenging to draw definitive conclusions regarding optimal interventions for individual patients [8]. One notable consequence of stroke is somatosensory impairment of the lower extremity, which affects a substantial proportion of stroke survivors, ranging between 45% and 56%, leading to difficulties in performing routine tasks [9, 10].
Sensory perception represents a fundamental modality for processing and interacting with the external environment [11, 12]. It enables the detection and discrimination of objects and textures, spatial awareness of body position (proprioception), and precise perception and differentiation of pain, temperature, pressure, and vibration sensations [13, 14]. Indeed, sensory perception is an essential element in human functioning, playing a pivotal role in facilitating normal physiological processes and influencing motor behaviors [13]. Notably, somatosensory input assumes particular significance in enabling accurate and adaptable motor control and in facilitating the acquisition of motor skills. This highlights the potential significance of sensory stimuli as a valuable constituent for enhancing motor rehabilitation strategies [15–17].
Recent advancements in neurorehabilitation have emphasized the critical role of somatosensory inputs in driving motor recovery through mechanisms such as neuroplasticity [18], proprioceptive feedback [19], and adaptive motor learning [19]. Sensory stimulation, particularly when applied to the plantar surface, activates mechanoreceptors and proprioceptive pathways, facilitating improved motor control and gait adaptations [20, 21]. These interventions are believed to stimulate brain regions involved in sensorimotor integration, thereby enhancing neuroplastic changes that support motor function recovery in stroke patients [22]. Technologies such as wearable sensors and robotic devices have further enhanced the precision and adaptability of these interventions, allowing for real-time feedback and individualized therapy adjustments [23]. For example, wearable devices can monitor gait parameters, providing immediate feedback to patients, while robotic devices can deliver consistent, controlled stimulation tailored to individual needs [24]. These technological innovations hold promise for improving the effectiveness of sensory-based rehabilitation strategies.
Despite the importance of somatosensory function in the lower limb, there is a lack of emphasis on rehabilitation interventions targeting this aspect. One such intervention, plantar sensory stimulation, involves activating the sensory receptors on the sole of the foot. However, the precise impact of plantar sensory stimulation on lower limb motor function and gait in stroke patients has not been clearly elucidated. Thus, the objective of this study was to conduct a systematic review and meta-analysis to investigate the effects of plantar sensory stimulation in improving lower limb motor function and gait in people with stroke.
Materials and methods
This study employs a rigorous and systematic methodology, consisting of a systematic review and meta-analysis, with strict adherence to the guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework [25]. To ensure utmost transparency and credibility, the protocol for this study has been officially registered at the International Prospective Register of Systematic Reviews (PROSPERO) with the registration number CRD42021290399 on December 21, 2021.
Inclusion and exclusion criteria
To guarantee the reliability and precision of our findings, the selected studies underwent an exhaustive screening process. We only considered randomized controlled trials involving adult patients aged above 18 years, diagnosed with stroke, and exhibiting motor impairments. Furthermore, to maintain consistency and coherence, the selected studies were required to have employed well-established assessments of lower limb motor function and gait in stroke patients. We also took into account studies investigating the effects of plantar sensory stimulation, either as a standalone intervention or when used in conjunction with other treatment regimens, thereby encompassing a comprehensive evaluation of its efficacy. In this review, we specifically considered research articles that were published in English. On the other hand, we deliberately excluded studies that solely focused on examining upper limb function in stroke patients. Additionally, studies involving participants under 18 years of age, those with bilateral stroke, or other neurological ailments were excluded.
Data sources search terms and search strategy
Our systematic review process rigorously adhered to the PRISMA guidelines, reflecting our commitment to conducting a comprehensive search for relevant literature. To ensure inclusivity, we conducted an extensive search of studies published from 1978 to September 2023, utilizing reputable and scholarly databases, specifically PubMed, Scopus, Web of Science, and Google Scholar (S1 Table). To enhance the reliability of our findings, two independent reviewers (AA and DS) diligently implemented the electronic search strategy within these databases, up to September 2023. Our search strategy employed relevant and precise terms related to stroke, plantar stimulation, lower limb motor function, and gait, thus maximizing the retrieval of pertinent studies. We judiciously combined free-text words and Medical Subject Headings (MeSH) terms using appropriate Boolean logic operators (AND and OR) to optimize the search results. Moreover, we adopted the Population, Intervention, Comparator, and Outcome (PICO) framework as the foundation of our research question, ensuring a focused and structured approach to our investigation.
Participants: Our study comprised a representative population of adults who had experienced their first stroke, diagnosed by qualified specialists, and were currently undergoing hospital-based inpatient or outpatient rehabilitation. We intentionally imposed no restrictions on participants’ ethnicity, gender, or other demographic features to ensure inclusivity and a more accurate reflection of the population under investigation.
Interventions: Our investigation meticulously considered studies that involved the application of plantar sensory stimulation on stroke patients, ascertaining its effects on lower limb motor function and gait. This approach allowed for a comprehensive assessment of the potential benefits of this intervention in a well-defined context, enhancing the robustness of our conclusions.
Outcome measures: To ensure a comprehensive evaluation of lower limb recovery, we thoroughly examined all clinical measures used to assess this aspect, encompassing assessments at two distinct time points (e.g., pre- to post-intervention). Our primary focus centered on examining gait and lower limb motor function, employing widely recognized and validated tools such as the Fugl-Meyer Assessment and the Rivermead Mobility Index, thereby ensuring the accuracy and reliability of our outcomes.
Control or comparator: We meticulously considered and analyzed different types of control interventions, such as no treatment, other active interventions, usual care, and sham interventions.
Study selection
All identified articles from the search strategy were exported to the CADIMA website, an open-access online tool established by Julius Kühn-Institut (JKI) for facilitating and documenting systematic reviews and further literature reviews (available at www.cadima.info). The CADIMA website automated the duplicate removal process and ensured an automated allocation of records during the screening process, considering the potential for independent and parallel assessment. Two independent reviewers, AA and DS, then screened the articles based on titles and abstracts, excluding studies that did not meet the eligibility criteria. Full texts from the selected studies were retrieved and thoroughly reviewed by both reviewers to determine their appropriateness for data extraction. In cases of disagreement regarding the eligibility of a study, AA and DS resolved the issue through a thorough review of the study criteria and discussion. Any remaining disagreements were resolved through consultation with the third reviewer, AS. Fig 1 presents the PRISMA flow chart, illustrating the search process of the study.
Data collection/extraction process
To ensure a comprehensive and unbiased approach, we independently verified the titles and abstracts of the selected studies. Through consensus and careful examination, any duplicate entries were diligently removed. The assessment of articles was executed with precision, adhering to the predetermined selection criteria and utilizing a well-structured data extraction form. Reviewers completed these forms independently, ensuring that all relevant information, including details on participants, interventions, controls, outcomes, methodologies, study designs, follow-up/retention strategies, and any reported adverse events, was accurately captured.
Data extraction
To ensure a thorough and unbiased approach, we independently verified the titles and abstracts of the selected studies. Through consensus and careful examination, any duplicate entries were diligently removed. The assessment of articles was executed with precision, following the predetermined selection criteria and utilizing a well-structured data extraction form. Reviewers completed these forms independently, ensuring all relevant information was captured, including details on participants, interventions, controls, outcomes, methodologies, study designs, follow-up/retention strategies, and any reported adverse events.
Data analysis
To assess the risk of bias in the studies we selected, we utilized the revised Cochrane risk of bias tool for randomized trials (RoB 2.0) [26]. This comprehensive tool facilitated a thorough evaluation of bias in five critical domains, which include bias arising from the randomization process, bias due to deviations from intended interventions, bias related to missing outcome data, bias in the measurement of outcomes, and bias in the selection of reported results. The data from the identified studies were analyzed using Review Manager software version 5.3. To determine the effect of plantar sensory stimulation compared to control conditions, we conducted random-effects meta-analyses on the reported outcome measures for gait and lower limb motor functions. Random-effects meta-analyses were chosen as the outcome measures estimating treatment effects varied across the studies. The effect size was calculated using the Standardized Mean Difference (SMD) due to the use of diverse outcome measures. SMD was calculated by the difference in mean outcome between groups divided by the standard deviation of outcomes [27]. For statistical significance, a P-value of less than 0.05 was considered significant. Additionally, for clinical significance, the SMD value was classified into small (SMD = 0.2), medium (SMD = 0.5), and large (SMD = 0.8) effects [27]. Heterogeneity was assessed using Cochrane’s I2 test, with the following thresholds as per Cochrane recommendations: 0%–40% (might not be important), 30%–60% (may represent moderate heterogeneity), and 50%–100% (may represent substantial heterogeneity) [27]. In the evaluation of publication bias, MedCalc software version 22.017 (MedCalc Software Ltd., Belgium) was employed to conduct both Egger’s and Begg’s tests.
Results
Study selection
The study selection process, illustrated in Fig 1, followed a structured and rigorous approach to ensure the inclusion of the most relevant and high-quality research articles related to the effects of plantar sensory stimulation on lower limb motor function and gait in stroke patients.
Initially, a comprehensive search was conducted across multiple databases and registers to identify potential studies. A total of 14,447 records were identified from various databases including PubMed (9,962 records), Scopus (1,205 records), Web of Science (1,000 records), and Google Scholar (2,280 records). Additionally, an alternative search method identified 7 more records from website sources (5 records) and citation searches (2 records).
Before any formal screening, 4,281 duplicate records were identified and removed, resulting in 10,166 unique records to be screened. The preliminary screening involved title assessment, wherein 9,990 records were excluded as they were deemed irrelevant to the research question. This was followed by an abstract-level screening, which further eliminated 149 records. At this juncture, 27 records were deemed potentially relevant and were selected for a full-text review. Concurrently, from the alternative search method, all seven records were considered for full-text review.
During the in-depth full-text review, several exclusion criteria were applied. For the primary database search, 18 studies were excluded because they did not focus on plantar sensory stimulation. Two studies were ruled out due to the inclusion of placebo, control, or other interventions that did not align with the review’s focus. Finally, three studies were removed as they did not specifically address lower limb motor function and gait outcomes. Similarly, for the alternative search method, three studies were excluded for not being randomized control trials.
Following these rigorous exclusion steps, a total of eight studies, each fitting the eligibility criteria perfectly, were included in the systematic review and meta-analysis. These studies form the foundation upon which the review’s findings and conclusions are built.
Risk of bias assessment
Our risk of bias assessment, employing the ROB2 tool and illustrated in Fig 2, yielded several key insights. Aries et al. (2021) emerged as the sole study with a consistent low risk across multiple categories [28]. In the realm of randomization processes, only Aries et al. (2021) was classified as low risk [28], while six other studies presented some concerns, and Aruin et al. (2012) was deemed high risk [29]. A notable high risk was identified in the deviations from intended interventions for seven studies, contrasting with Aries et al. (2021) which remained at low risk [28]. When evaluating bias due to missing outcome data, seven studies demonstrated a low risk, leaving Mohapatra et al. (2012) as the only high-risk entity [30]. In the assessment of outcome measurement bias, three studies were characterized as low risk, while the remaining five exhibited a high-risk profile. Impressively, all included studies uniformly presented a low risk of bias in the selection of reported results, underscoring a degree of reliability in this domain.
The figure summarizes the risk of bias across key domains, including randomization, blinding, and outcome reporting. Green indicates low risk, yellow represents some concerns, and red denotes high risk.
Participants
This systematic review comprised a total of 215 participants. The mean time since stroke onset varied from 11 days [30] to 6 years [31]. Regarding stroke type, five studies included participants with both ischemic and hemorrhagic stroke [28, 30, 32–34]. One study exclusively enrolled participants with ischemic stroke [35], while two studies did not provide details about the stroke type [29, 31]. The summary of the included studies is presented in Table 1.
As shown in Table 1, improvements in somatosensory subdomains, such as touch-pressure thresholds, were observed [28, 33]. These findings suggest that interventions, such as textured insoles and cognitive sensorimotor exercises, may enhance specific aspects of sensory function. However, other studies did not report significant changes in somatosensory measures or did not assess these subdomains at all. The inconsistency in outcomes may be attributed to variations in the type, intensity, and duration of the interventions, or differences in baseline sensory impairments across participants.
Intervention
Several different sensory stimulation techniques were employed in the included trials. Two trials utilized textured insoles as the sensory stimulation [28, 31]. Two studies used compelled body weight shift using uneven insoles [29, 30]. One study used customized insoles [34]. One study implemented sensorimotor foot stimulation [35], encompassing interventions such as improving flexibility of soft tissues around the ankle and foot, enhancing foot sensation through various tactile techniques, and promoting selective movements within the ankle joint using visual, auditory, and sensory stimuli. Additionally, this study focused on standing on surfaces with different textures. One study used task-specific training combined with cognitive sensorimotor exercise which consisted of proprioceptive training, tactile training, heel pressure, and spatial tasks [33]. Another study employed plantar vibration as the sensory stimulation [32]. Time for the intervention was from 20 min to 60 min, intervention ranged from three sessions per week [31] to six sessions per week [35]. Duration of intervention was from two weeks [30] to eight weeks [33].
Six included studies evaluated lower limb motor function using the following outcome measures: Modified Rivermead Mobility Index [28], Fugl-Meyer Lower Extremity Score [30, 31, 34], Fugl Meyer Assessment Scale [35], and Timed-Up and Go test [32]. The estimates of treatment effect and standardized mean difference for the studies measuring lower limb motor function are presented in Table 2. Additionally, seven of the studies assessed gait using the following outcome measures: 5-meter walk test [28], 10-meter walk test [32], and gait velocity [29–31, 33], and Tinetti Gait Scale [34]. The estimates of treatment effect and standardized mean difference for the studies measuring gait are shown in Table 3. Only one study of the included studies monitored adverse effects of pain and fatigue on the participants [28]. The psychometric properties of the outcome measures used in this review are summarized in Table 4. Notably, most measures demonstrated excellent reliability and validity, particularly the Fugl-Meyer Lower Extremity Score and the Modified Rivermead Mobility Index. However, there is a lack of data on the MCID for several measures, including the Timed-Up and Go test and the 5-Meter Walk Test, suggesting the need for further research to establish clinical benchmarks.
Effect of plantar sensory stimulation on lower limb motor function
The forest plot in Fig 3 illustrates the effect of plantar sensory stimulation on lower limb motor function, showing a medium effect size (SMD = 0.75 [95% CI = 0.23–1.28]; P = 0.005; I2 = 59%), indicating moderate heterogeneity across studies. To explore the sources of this heterogeneity, subgroup analyses were conducted based on the type of sensory intervention. The analyses revealed that specific types of plantar somatosensory stimulation, such as tactile stimulation or textured insoles, demonstrated a more consistent effect, with a medium effect size (SMD = 0.58 [95% CI = 0.24–0.92]; P = 0.0009; I2 = 0%), suggesting that the more uniform application of these interventions helped to reduce variability. In contrast, studies using plantar vibration produced a large effect size (SMD = 2.03 [95% CI = 1.13–2.94]; P < 0.0001), but heterogeneity was not applicable due to data from a single trial. This indicates that variations in intervention type and application protocols contributed to the overall heterogeneity observed. The analysis revealed an absence of significant publication bias for the lower limb motor function, as evidenced by the results of Egger’s test (intercept = -0.53, 95% CI = -0.871 to 7.65, P = 0.87) and Begg’s test (Kendall’s Tau = -0.20, P = 0.57).
Effect of plantar sensory stimulation on gait
For gait outcomes, the forest plot in Fig 4 shows a large overall effect size (SMD = 1.38 [95% CI = 0.42–2.33]; P = 0.005; I2 = 85%), reflecting high heterogeneity. Subgroup analyses based on the type of sensory intervention provided further insights. While interventions like plantar somatosensory stimulation delivered via textured insoles or tactile methods showed moderate and varied results (SMD = 0.50 [95% CI = -0.07–1.06]; P = 0.08; I2 = 45%), other approaches such as plantar vibration and cognitive sensorimotor training demonstrated large effect sizes (SMD = 3.17 [95% CI = 2.05–4.29]; SMD = 2.85 [95% CI = 1.69–4.02], respectively) with lower variability within their subgroups (I2 not applicable for single trials). These findings suggest that the type, intensity, and consistency of interventions, along with patient-specific factors, played a role in the heterogeneity observed across studies. Subsequently, the analysis revealed an absence of significant publication bias for the gait, as evidenced by the results of Egger’s test (intercept = 5.4, 95% CI = -0.73 to 11.59, P = 0.07) and Begg’s test (Kendall’s Tau = 0.43, P = 0.18).
Discussion
Stroke stands as one of the foremost causes of long-term disability worldwide, profoundly affecting the adult population and presenting a global health challenge [58, 59]. The rehabilitation journey post-stroke is multifaceted, with paramount emphasis on reviving voluntary activity in the hemiparetic lower extremity and recuperating the ability to walk autonomously [31, 60, 61]. Such recovery is instrumental in enabling stroke survivors to reclaim their independence, reintegrate into societal settings, and enjoy a quality of life akin to their pre-stroke state. Yet, while the quest for effective rehabilitation methods continues, a pronounced lacuna exists regarding the potential of plantar sensory stimulation as a rehabilitative intervention for lower limb motor function and gait among stroke patients. Our research ambitiously sought to fill this knowledge chasm through an exhaustive systematic review and meta-analysis of the available literature.
Emerging from our investigation is the revelation that plantar sensory stimulation offers a promising avenue for enhancing lower limb motor functionality, as evidenced by a medium effect size (SMD = 0.75). Delving deeper into the modalities, the subgroup analysis shone light on specific techniques, particularly the use of textured insoles or tactile stimulations, that exhibited tangible improvements, indicated by a medium effect size (SMD = 0.58). Furthermore, the efficacy of plantar vibration was unmistakably underscored, showcasing a large effect size (SMD = 2.03). Such data not only provides empirical support for plantar sensory stimulation’s potential but also offers insights into the intricate neurophysiological processes possibly at work. As elucidated by Bonassi et al. (2017), the underpinnings of these improvements may lie in the realm of neuroplasticity, with sensory-based interventions acting as catalysts for adaptive motor cortical changes—a potent mechanism facilitating post-stroke recovery [62].
The interpretation of these findings is strengthened using outcome measures with robust psychometric properties. In our review, measures such as the Fugl-Meyer Lower Extremity Score and the Modified Rivermead Mobility Index exhibited excellent reliability and known MCID values, supporting the clinical relevance of the improvements observed. However, it is important to note that certain measures, like the Timed-Up and Go test and 5-Meter Walk Test, lacked comprehensive data on MCID, which limits our ability to fully assess the clinical significance of changes. Future studies should aim to establish these psychometric benchmarks to improve the consistency and interpretability of rehabilitation outcomes in this field.
Our analysis of lower limb motor function and gait outcomes demonstrated varying levels of effectiveness across different interventions. For lower limb motor function, studies like Wang (2021) showed significant improvements on the Fugl-Meyer Lower Extremity Assessment, with a mean change of 7 (1.86) and an SMD of 0.83 [34], surpassing known MDC thresholds of 1.3 [36], indicating reliable and clinically meaningful gains. Similarly, the Modified Rivermead Mobility Index (mRMI) in Aries (2021) showed moderate improvement with an SMD of 0.71 [28]. In contrast, Mohapatra (2012) displayed limited effectiveness with negative effect sizes [30], suggesting variability in response to certain interventions. For gait outcomes, the 10-Meter Walk Test in Önal (2022) reported a mean improvement of -4.75 (1.48) seconds with an SMD of 3.17 [32], indicating substantial gains in walking speed. Furthermore, gait velocity improvements seen in Kim (2021) and Mohapatra (2012) exceeded the MCID of 0.18–0.25 m/s [54], underscoring the clinical relevance of these changes. These findings suggest that interventions combining sensory stimulation with motor training can lead to robust outcomes in lower limb rehabilitation.
Parallel to these findings, our study also highlights the instrumental role of sensory input in bolstering stroke recovery [63]. Historically, the emphasis in stroke rehabilitation has often veered more towards motor function, perhaps overlooking the symbiotic relationship between sensory and motor recovery. While the significance of sensory feedback in shaping motor responses is increasingly recognized, its full potential remains largely untapped in clinical rehabilitation [12, 64]. Consequently, our findings serve as a clarion call for both deeper research endeavors into sensory stimulation techniques and their subsequent infusion into mainstream rehabilitative practices.
In assessing gait improvements, our findings were compelling. Plantar sensory stimulation emerged as a formidable intervention, eliciting substantial enhancements in gait metrics with a large effect size (SMD = 1.38). Further granularity provided by the subgroup analyses reaffirmed the benefits of both plantar vibration and cognitive sensorimotor training. The implications of these findings are vast, suggesting not only the merit of sensory interventions but also hinting at the potential neurological pathways they may engage.
The variability observed in effect sizes and mean differences across studies could be attributed to several factors, including differences in intervention protocols, intensity, and participant characteristics. Interventions that combined physical therapy with sensory inputs, such as textured insoles or vibration therapy, generally produced stronger outcomes. This indicates a synergistic effect that might not be present with standard rehabilitation alone.
Plantar somatosensory stimulation, such as the use of textured insoles, primarily targets foot sensory receptors, enhancing feedback to the central nervous system, which may contribute to improved motor function and balance. This mechanism is likely to drive motor recovery by fostering sensory-motor integration, providing continuous low-level input that aids in maintaining balance and stability [62]. However, the effects observed with textured insoles were moderate, possibly due to the passive nature of the stimulation, which may not always provide sufficient intensity to produce significant changes across all motor functions. In contrast, plantar vibration involves sub-threshold stimulation that activates proprioceptive receptors more directly, leading to an increase in sensory input [65]. This more intensive, direct engagement of sensory pathways might explain the larger effect sizes observed in gait improvements, as the vibration enhances proprioceptive feedback and sensory-motor integration specific to gait. Additionally, vibratory stimulation has been linked to reduced variability in toe clearance during walking, leading to more consistent and stable gait patterns [66]. The targeted, dynamic nature of vibratory feedback may therefore offer a stronger influence on gait-related outcomes compared to the more general stimulation provided by textured insoles.
Our risk of bias assessment, conducted using the ROB2 tool, revealed varying levels of methodological quality across the included studies. While Aries et al. (2021) demonstrated a consistently low risk across multiple domains, other studies presented concerns [28]. For instance, six studies had issues with the randomization process, and Aruin et al. (2012) was deemed high risk in this domain [29]. Additionally, seven studies showed a high risk of deviations from intended interventions, which might have impacted adherence to protocols. Outcome measurement bias was notably high in five studies, indicating possible inconsistencies in how outcomes were assessed and reported. However, all studies maintained a low risk of bias regarding the selection of reported results, which suggests reliable reporting. These varying levels of bias may affect the generalizability of the findings, emphasizing the need for future studies to improve on aspects such as randomization, blinding, and intervention consistency.
The observed improvements in somatosensory function, particularly in tactile sensation, suggest that specific interventions such as textured insoles, cognitive sensorimotor exercises, and somatosensory stimulation can effectively enhance sensory feedback in stroke survivors. Electrical stimulation applied to the paretic foot significantly improved precision in foot placement, especially among individuals with greater impairment, indicating that targeted sensory inputs can enhance motor control [67]. Similarly, retraining leg somatosensory function led to significant improvements in balance, although gait enhancements were not as pronounced, suggesting that while sensory retraining can improve stability, more refined approaches may be needed to impact gait directly [68]. Integrating somatosensory training with standard physical therapy also resulted in better neuromuscular control, as evidenced by improvements in Functional Independent Measure and Electroencephalography scores, highlighting the role of sensory retraining in supporting functional and neural recovery [69]. These findings align with the idea that stimulating sensory receptors through continuous or targeted inputs can help re-establish neural pathways disrupted by stroke.
However, the variability in the effectiveness of these interventions across studies indicates that factors such as the type of sensory impairment, the intensity of interventions, or the specific sensory subdomains targeted may influence outcomes. Future research should explore whether certain aspects of sensory function, like proprioception, require more intensive or prolonged stimulation to achieve significant improvements and how these interventions can be optimized to enhance both balance and gait recovery.
This study, though illuminating, has its limitations. The comprehensive search strategy excluded non-English publications and non-randomized controlled trials. The meta-analysis was grounded in a limited set of randomized controlled trials, which may have impacted statistical potency. Additionally, the absence of established psychometric benchmarks such as MCID for certain outcome measures, including the Timed-Up and Go test and 5-Meter Walk Test, limits the ability to fully interpret the clinical relevance of the observed changes. Future research should focus on standardizing these measures and establishing robust psychometric data to allow for more consistent comparisons across studies. Inconsistencies in study protocols and outcome measures across investigations contributed to identified statistical heterogeneity. With some subgroups anchored by just one study, interpretation becomes complex. Therefore, future studies should strive to unify outcome measurements for lower limb motor function and gait to allow for more robust comparisons and draw firmer conclusions.
Conclusion
Our systematic review and meta-analysis revealed a noteworthy positive influence of plantar sensory stimulation on both lower limb motor function and gait in stroke patients. Various techniques, such as plantar somatosensory stimulation, plantar vibration, and cognitive sensorimotor training, demonstrated significant enhancement in motor function and gait outcomes compared to control groups. Notably, the use of plantar somatosensory stimulation, particularly employing textured insoles or tactile methods, and plantar vibration yielded medium to large effect sizes, indicating their potential efficacy in rehabilitation for stroke patients. This review underscores the importance of plantar sensory stimulation techniques in post-stroke recovery, emphasizing the need for more extensive and randomized controlled trials to further elucidate the optimal techniques and parameters for maximizing therapeutic outcomes.
Future research should explore the benefits of combining sensory stimulation with motor training exercises, as integrating both modalities could enhance motor learning and overall recovery. Additionally, incorporating new technologies, such as wearable sensors and robotic devices, may provide real-time feedback and adaptive stimulation, leading to more precise and effective interventions. To improve the comparability and reproducibility of results, standardizing intervention protocols—such as the duration, intensity, and frequency of sensory stimulation—across studies will be essential. Advancing these areas will help establish more effective rehabilitation strategies and maximize motor recovery outcomes for individuals with stroke.
Supporting information
S1 Table. Search term of studies published from 1978 to September 2023, utilizing reputable and scholarly databases.
https://doi.org/10.1371/journal.pone.0315097.s002
(DOCX)
S2 Table. Studies identified and excluded with reasons.
https://doi.org/10.1371/journal.pone.0315097.s003
(DOCX)
References
- 1. Kochanek KD, Kirmeyer SE, Martin JA, Strobino DM, Guyer BJP. Annual summary of vital statistics: 2009. 2012;129(2):338–48. pmid:22291121
- 2. Ovbiagele B, Goldstein LB, Higashida RT, Howard VJ, Johnston SC, Khavjou OA, et al. Forecasting the future of stroke in the United States: a policy statement from the American Heart Association and American Stroke Association. 2013;44(8):2361–75. pmid:23697546
- 3. Almkvist Muren M, Hütler M, Hooper JJTisr. Functional capacity and health-related quality of life in individuals post stroke. 2008;15(1):51–8. pmid:18250074
- 4. Smith PS, Thompson MJCr. Treadmill training post stroke: are there any secondary benefits? A pilot study. 2008;22(10–11):997–1002.
- 5. van Swigchem R, van Duijnhoven HJ, den Boer J, Geurts AC, Weerdesteyn V. Deficits in motor response to avoid sudden obstacles during gait in functional walkers poststroke. Neurorehabil Neural Repair. 2013;27(3):230–9. pmid:23077147
- 6. Benjamin EJ, Muntner P, Alonso A, Bittencourt MS, Callaway CW, Carson AP, et al. Heart disease and stroke statistics—2019 update: a report from the American Heart Association. 2019;139(10):e56–e528. pmid:30700139
- 7. Thom T, Haase N, Rosamond W, Howard VJ, Rumsfeld J, Manolio T, et al. Heart disease and stroke statistics—2006 update: a report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. 2006;113(6):e85–e151. pmid:16407573
- 8. Pollock A, Baer G, Campbell P, Choo PL, Forster A, Morris J, et al. Physical rehabilitation approaches for the recovery of function and mobility following stroke. 2014;(4). pmid:24756870
- 9. Tyson SF, Crow JL, Connell L, Winward C, Hillier SJTisr. Sensory impairments of the lower limb after stroke: a pooled analysis of individual patient data. 2013;20(5):441–9. pmid:24091286
- 10. Gorst T, Rogers A, Morrison S, Cramp M, Paton J, Freeman J, et al. The prevalence, distribution, and functional importance of lower limb somatosensory impairments in chronic stroke survivors: a cross sectional observational study. 2018;41(20):2443–50. pmid:29726732
- 11. Connell LA. Sensory impairment and recovery after stroke: University of Nottingham Nottingham; 2007.
- 12. Carey LM, Lamp G, Turville M. The State-of-the-Science on Somatosensory Function and Its Impact on Daily Life in Adults and Older Adults, and Following Stroke: A Scoping Review. OTJR: occupation, participation and health. 2016;36(2 Suppl):27s–41s. Epub 2016/08/10. pmid:27504989.
- 13. Doyle S, Bennett S, Fasoli SE, McKenna KT. Interventions for sensory impairment in the upper limb after stroke. J Cochrane Database of Systematic Reviews. 2010;(6).
- 14. Carey LM, Matyas TA, Baum C. Effects of somatosensory impairment on participation after stroke. American Journal of Occupational Therapy. 2018;72(3):7203205100p1–p10. pmid:29689179
- 15. Wu CW, Seo H-J, Cohen LG. Influence of electric somatosensory stimulation on paretic-hand function in chronic stroke. Arch Phys Med Rehabil. 2006;87(3):351–7. pmid:16500168
- 16. Yekutiel M, Guttman E. A controlled trial of the retraining of the sensory function of the hand in stroke patients. J Neurol Neurosurg Psychiatry. 1993;56(3):241–4. pmid:8459238
- 17. Celnik P, Hummel F, Harris-Love M, Wolk R, Cohen LG. Somatosensory stimulation enhances the effects of training functional hand tasks in patients with chronic stroke. Arch Phys Med Rehabil. 2007;88(11):1369–76. pmid:17964875
- 18. Schaechter JD, van Oers CAMM, Groisser BN, Salles SS, Vangel MG, Moore CI, et al. Increase in Sensorimotor Cortex Response to Somatosensory Stimulation Over Subacute Poststroke Period Correlates With Motor Recovery in Hemiparetic Patients. Neurorehabilitation and Neural Repair. 2011;26(4):325–34. pmid:21952198
- 19. Mirdamadi JL, Block HJ. Somatosensory changes associated with motor skill learning. Journal of Neurophysiology. 2020;123(3):1052–62. pmid:31995429
- 20. Alfuth M, Rosenbaum D. Effects of changes in plantar sensory feedback on human gait characteristics: a systematic review. Footwear Science. 2012;4(1):1–22.
- 21. Oku K, Kimura D, Matsugi A, Inoue J, Hattori A, Nakano H, et al. Improvement of Gait Function by Increasing the Contribution of Peripheral Sensation from the Ankle during Postural Control in a Patient with Stroke: A Case Report. Rigakuryoho kagaku. 2016;31(2):355–60.
- 22. Li W, Li C, Liu A, Lin P-J, Mo L, Zhao H, et al. Lesion-specific cortical activation following sensory stimulation in patients with subacute stroke. Journal of NeuroEngineering and Rehabilitation. 2023;20(1). pmid:37957755
- 23. Adans-Dester CP, Lang CE, Reinkensmeyer DJ, Bonato P. Wearable Sensors for Stroke Rehabilitation. Neurorehabilitation Technology 2022. p. 467–507.
- 24. Graczyk E, Hutchison B, Valle G, Bjanes D, Gates D, Raspopovic S, et al. Clinical Applications and Future Translation of Somatosensory Neuroprostheses. The Journal of Neuroscience. 2024;44(40). pmid:39358021
- 25. Ayache SS, Farhat WH, Zouari HG, Hosseini H, Mylius V, Lefaucheur JP. Stroke rehabilitation using noninvasive cortical stimulation: motor deficit. Expert Rev Neurother. 2012;12(8):949–72. Epub 2012/09/26. pmid:23002939.
- 26. Sterne JAC, Savovic J, Page MJ, Elbers RG, Blencowe NS, Boutron I, et al. RoB 2: a revised tool for assessing risk of bias in randomised trials. BMJ. 2019;366:l4898. pmid:31462531.
- 27.
Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, et al. Cochrane Handbook for Systematic Reviews of Interventions. 2nd ed. UK: John Wiley & Sons, Chichester; 2019. 694 p.
- 28. Aries AM, Pomeroy VM, Sim J, Read S, Hunter SM. Sensory Stimulation of the Foot and Ankle Early Post-stroke: A Pilot and Feasibility Study. Frontiers in Neurology. 2021;12(940):1–24. pmid:34290663
- 29. Aruin AS, Rao N, Sharma A, Chaudhuri G. Compelled body weight shift approach in rehabilitation of individuals with chronic stroke. Top Stroke Rehabil. 2012;19(6):556–63. pmid:23192720; PubMed Central PMCID: PMC3676671.
- 30. Mohapatra S, Eviota AC, Ringquist KL, Muthukrishnan SR, Aruin AS. Compelled Body Weight Shift Technique to Facilitate Rehabilitation of Individuals with Acute Stroke. ISRN Rehabil. 2012;2012. pmid:25530888; PubMed Central PMCID: PMC4269244.
- 31. Aruin AS, Rao N. The effect of a single textured insole in gait rehabilitation of individuals with stroke. Int J Rehabil Res. 2018;41(3):218–23. pmid:29649054.
- 32. Önal B, Sertel M, Karaca G. Effect of plantar vibration on static and dynamic balance in stroke patients: a randomised controlled study. Physiotherapy. 2022;116:1–8. Epub 20220214. pmid:35462214.
- 33. Kim KH, Jang SH. Effects of Task-Specific Training after Cognitive Sensorimotor Exercise on Proprioception, Spasticity, and Gait Speed in Stroke Patients: A Randomized Controlled Study. Medicina (Kaunas). 2021;57(10). Epub 20211013. pmid:34684135; PubMed Central PMCID: PMC8541560.
- 34. Wang J, Qiao L, Yu L, Wang Y, Taiar R, Zhang Y, et al. Effect of Customized Insoles on Gait in Post-Stroke Hemiparetic Individuals: A Randomized Controlled Trial. Biology (Basel). 2021;10(11). Epub 20211115. pmid:34827179; PubMed Central PMCID: PMC8614694.
- 35. Goliwąs M, Kocur P, Wernicka M, Kaminska E, Lewandowski J. Effect of sensorimotor foot stimulation on the body postural, function and load of the lower limb in patients in the late. Fizjoterapia Polska. 2017;17:24–35.
- 36. Tsang RC-C, Chau RM-W, Cheuk TH-W, Cheung BS-P, Fung DM-Y, Ho EY-L, et al. The measurement properties of modified Rivermead mobility index and modified functional ambulation classification as outcome measures for Chinese stroke patients. Physiotherapy Theory and Practice. 2014;30(5):353–9. pmid:24400683
- 37. Walsh JM, Barrett A, Murray D, Ryan J, Moroney J, Shannon M. The Modified Rivermead Mobility Index: Reliability and convergent validity in a mixed neurological population. Disability and Rehabilitation. 2010;32(14):1133–9. pmid:20131953
- 38. Rådman L, Forsberg A, Nilsagård Y. Modified Rivermead Mobility Index: a reliable measure in people within 14 days post-stroke. Physiotherapy Theory and Practice. 2014;31(2):126–9. pmid:25238211
- 39. Nakazono T, Takahashi K, Suzuki Y, Mizuno K, Nomura Y, Hiraga Y, et al. Reliability and validity of Japanese version of Fugl-Meyer assessment for the lower extremities. Topics in Stroke Rehabilitation. 2021;29(2):125–32. pmid:33724162
- 40. Hernández ED, Forero SM, Galeano CP, Barbosa NE, Sunnerhagen KS, Alt Murphy M. Intra- and inter-rater reliability of Fugl-Meyer Assessment of Lower Extremity early after stroke. Brazilian Journal of Physical Therapy. 2021;25(6):709–18. pmid:33358073
- 41. Kim H, Her J, Ko J, Park D-s, Woo J-H, You Y, et al. Reliability, Concurrent Validity, and Responsiveness of the Fugl-Meyer Assessment (FMA) for Hemiplegic Patients. Journal of Physical Therapy Science. 2012;24(9):893–9.
- 42. Lundquist CB, Maribo T. The Fugl–Meyer assessment of the upper extremity: reliability, responsiveness and validity of the Danish version. Disability and Rehabilitation. 2016;39(9):934–9. pmid:27062881
- 43. Hsieh Y-w Wu C-y, Lin K-c Chang Y-f, Chen C-l Liu J-s. Responsiveness and Validity of Three Outcome Measures of Motor Function After Stroke Rehabilitation. Stroke. 2009;40(4):1386–91. pmid:19228851
- 44. Huynh BP, DiCarlo JA, Vora I, Ranford J, Gochyyev P, Lin DJ, et al. Sensitivity to Change and Responsiveness of the Upper Extremity Fugl-Meyer Assessment in Individuals With Moderate to Severe Acute Stroke. Neurorehabilitation and Neural Repair. 2023;37(8):545–53. pmid:37483132
- 45. Hafsteinsdóttir TB, Rensink M, Schuurmans M. Clinimetric Properties of the Timed Up and Go Test for Patients With Stroke: A Systematic Review. Topics in Stroke Rehabilitation. 2014;21(3):197–210. pmid:24985387
- 46. Alghadir AH, Al-Eisa ES, Anwer S, Sarkar B. Reliability, validity, and responsiveness of three scales for measuring balance in patients with chronic stroke. BMC Neurology. 2018;18(1). pmid:30213258
- 47. Salbach NM, Mayo NE, Higgins J, Ahmed S, Finch LE, Richards CL. Responsiveness and predictability of gait speed and other disability measures in acute stroke. Archives of Physical Medicine and Rehabilitation. 2001;82(9):1204–12. pmid:11552192
- 48. Cheng DK, Nelson M, Brooks D, Salbach NM. Validation of stroke-specific protocols for the 10-meter walk test and 6-minute walk test conducted using 15-meter and 30-meter walkways. Topics in Stroke Rehabilitation. 2019;27(4):251–61. pmid:31752634
- 49. Busk H, Holm P, Skou ST, Seitner S, Siemsen T, Wienecke T. Inter-rater reliability and agreement of 6 Minute Walk Test and 10 Meter Walk Test at comfortable walk speed in patients with acute stroke. Physiotherapy Theory and Practice. 2022;39(5):1024–32. pmid:35109744
- 50. Lin J-H, Hsu M-J, Hsu H-W, Wu H-C, Hsieh C-L. Psychometric Comparisons of 3 Functional Ambulation Measures for Patients With Stroke. Stroke. 2010;41(9):2021–5. pmid:20671244
- 51. Tilson JK, Sullivan KJ, Cen SY, Rose DK, Koradia CH, Azen SP, et al. Meaningful Gait Speed Improvement During the First 60 Days Poststroke: Minimal Clinically Important Difference. Physical Therapy. 2010;90(2):196–208. pmid:20022995
- 52. Liaw L-J, Hsieh C-L, Lo S-K, Lee S, Huang M-H, Lin J-H. Psychometric properties of the modified Emory Functional Ambulation Profile in stroke patients. Clinical Rehabilitation. 2006;20(5):429–37. pmid:16774094
- 53. Agustín RM-S, Crisostomo MJ, Sánchez-Martínez MP, Medina-Mirapeix F. Responsiveness and Minimal Clinically Important Difference of the Five Times Sit-to-Stand Test in Patients with Stroke. International Journal of Environmental Research and Public Health. 2021;18(5). pmid:33652864
- 54. Hayashi S, Miyata K, Takeda R, Iizuka T, Igarashi T, Usuda S. Minimal clinically important difference of the Berg Balance Scale and comfortable walking speed in patients with acute stroke: A multicenter, prospective, longitudinal study. Clinical Rehabilitation. 2022;36(11):1512–23. pmid:35730136
- 55. Arranz–Escudero A, Martín–Casas P, Carpio–Calatayud E, López–de–Uralde–Villanueva I. Validez convergente de la escala Tinetti en pacientes con ictus en fase subaguda. Revista Científica de la Sociedad Española de Enfermería Neurológica. 2024.
- 56. Canbek J, Fulk G, Nof L, Echternach J. Test-Retest Reliability and Construct Validity of the Tinetti Performance-Oriented Mobility Assessment in People With Stroke. Journal of Neurologic Physical Therapy. 2013;37(1):14–9. pmid:23389388
- 57. Taghavi Azar Sharabiani P, Mehdizadeh M, Goudarzi S, Jamali S, Mazhar FN, Heidari M, et al. Minimal important difference of Berg Balance Scale, performance-oriented mobility assessment and dynamic gait index in chronic stroke survivors. Journal of Stroke and Cerebrovascular Diseases. 2024;33(11). pmid:39213837
- 58. Langhorne P, Bernhardt J, Kwakkel G. Stroke rehabilitation. Lancet. 2011;377(9778):1693–702. pmid:21571152.
- 59. Sturm JW, Dewey HM, Donnan GA, Macdonell RA, McNeil JJ, Thrift AG. Handicap after stroke: how does it relate to disability, perception of recovery, and stroke subtype?: the north North East Melbourne Stroke Incidence Study (NEMESIS). Stroke. 2002;33(3):762–8. pmid:11872901.
- 60. Lord SE, McPherson K, McNaughton HK, Rochester L, Weatherall M. Community ambulation after stroke: how important and obtainable is it and what measures appear predictive? Arch Phys Med Rehabil. 2004;85(2):234–9. Epub 2004/02/18. pmid:14966707.
- 61. Vestling M, Tufvesson B, Iwarsson S. Indicators for return to work after stroke and the importance of work for subjective well-being and life satisfaction. Journal of rehabilitation medicine. 2003;35(3):127–31. pmid:12809195
- 62. Bonassi G, Biggio M, Bisio A, Ruggeri P, Bove M, Avanzino L. Provision of somatosensory inputs during motor imagery enhances learning-induced plasticity in human motor cortex. Scientific Reports. 2017;7(1). pmid:28839226
- 63. Schabrun SM, Hillier S. Evidence for the retraining of sensation after stroke: a systematic review. Clinical rehabilitation. 2009;23(1):27–39. pmid:19114435
- 64. de Diego C, Puig S, Navarro X. A sensorimotor stimulation program for rehabilitation of chronic stroke patients. Restor Neurol Neurosci. 2013;31(4):361–71. Epub 2013/03/26. pmid:23524843.
- 65. Felicetti G, Thoumie P, Do MC, Schieppati M. Cutaneous and muscular afferents from the foot and sensory fusion processing: Physiology and pathology in neuropathies. Journal of the Peripheral Nervous System. 2021;26(1):17–34. pmid:33426723
- 66. Weber DJ, Pathak P, Moon J, Roh S-g, Roh C, Shim Y, et al. Application of vibration to the soles reduces minimum toe clearance variability during walking. Plos One. 2022;17(1):e0261732. pmid:34982783
- 67. Walker ER, Hyngstrom AS, Schmit BD. Sensory electrical stimulation improves foot placement during targeted stepping post-stroke. Experimental Brain Research. 2014;232(4):1137–43. pmid:24449007
- 68. Chia FSF, Kuys S, Low Choy N. Sensory retraining of the leg after stroke: systematic review and meta-analysis. Clinical Rehabilitation. 2019;33(6):964–79. pmid:30897960
- 69. Alwhaibi R M., Mahmoud NF, Basheer MA, M. Zakaria H, Elzanaty MY, Ragab WM, et al. Impact of Somatosensory Training on Neural and Functional Recovery of Lower Extremity in Patients with Chronic Stroke: A Single Blind Controlled Randomized Trial. International Journal of Environmental Research and Public Health. 2021;18(2). pmid:33445588