The Effects of Ankle Versus Plantar Vibrotactile Orthoses on Joint Position Sense and Postural Control in Individuals with Functional Ankle Instability: A Pilot Randomized Trial

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is very well prepared. The subject of the study is very interesting, However there are some concerns regarding the research question and methodology.

-It is not clear why the researchers compare VFO and VAO. This is a very important question which should be justified clearly.

-Please provide more information regarding the foot posture of the participants.

-Please provide references for stimulation protocol. 

-Why did you include individuals with fracture history or advanced age only to exclude them later (figure 5)?

-Please provide references that let you moderate type 1 and type 2 errors for estimating the sample size.

-The discussion does not support the likely differences of the injured ankle stimulation demands and plantar region. 

-The sample size is a concern for interpretation of the results, however the term "pilot" make the readers more cautious in generalizing the findings.

Author Response

Reply to reviewers

Manuscript: bioengineering-4036402- “The Effects of Ankle versus Plantar Vibrotactile Orthoses on Joint Position Sense and Postural Control in Individuals with Functional Ankle Instability: A Pilot Randomized Trial”

 

Reviewer 1

The paper is very well prepared. The subject of the study is very interesting, However there are some concerns regarding the research question and methodology.

 

Dear Reviewer,

Thank you very much for reviewing our manuscript and providing us with specific comments. We have included your comments immediately after this letter and responded individually. The comments are in black, and our responses are in blue. The changes made have been highlighted (in yellow) within the manuscript.

With regards,

Corresponding authors

 

-It is not clear why the researchers compare VFO and VAO. This is a very important question which should be justified clearly.

The rationale for comparing vibrotactile foot orthoses (VFO) and vibrotactile ankle orthoses (VAO) lies in the distinct sensory contributions of the lateral ankle region versus the plantar surface of the foot. Prior evidence has shown that cutaneous feedback from the lateral ankle plays a critical role in modulating eversion movements, as mechanoreceptors in this area detect joint position changes during inversion-eversion and transmit them to the central nervous system. In FAI, collagen fibers in the lateral ankle skin remain structurally intact, but the mechanoreceptors are more vulnerable to injury during sprains due to their lower tensile tolerance compared to connective tissue. This damage contributes to impaired afferent input.

At the same time, plantar mechanoreceptors provide abundant proprioceptive information related to touch, pressure, and joint movement. It remains unclear whether vibrotactile stimulation applied at the ankle or at the plantar surface is more effective in restoring joint position sense and postural control in individuals with FAI. Therefore, our study directly compared VFO and VAO to address this gap.

We add the following text to the introduction section:

“Previous studies have highlighted the role of lateral ankle cutaneous feedback in regulating eversion movements, as mechanoreceptors in this region detect inversion-eversion changes and transmit them to the CNS [9]. In FAI, collagen fibers of the lateral ankle skin remain structurally intact, but mechanoreceptors are more susceptible to injury during sprains due to their lower tensile tolerance compared to connective tissue [8]. This damage contributes to impaired afferent input. Also, the plantar surface of the foot contains a high density of mechanoreceptors that provide proprioceptive information related to touch, pressure, and joint movement [15,16]. It is not yet clear whether vibrotactile stimulation applied at the ankle or at the plantar surface is more effective in improving joint position sense and postural control in individuals with FAI.”

 

-Please provide more information regarding the foot posture of the participants.

 

In this study, only participants with normal foot posture were included. To ensure this, we used the Foot Posture Index (FPI-6), a validated clinical tool for assessing foot posture. The FPI-6 evaluates six criteria (including talar head palpation, supra- and infra-lateral malleolar curvature, calcaneal frontal plane position, talonavicular bulging, arch height, and forefoot-to-rearfoot alignment) with each item scored from -2 to +2. The total score ranges from -12 (highly supinated/pes cavus) to +12 (highly pronated/pes planus).

Participants with scores indicating pes planus (flat foot, FPI ≥ +6) or pes cavus (high arch, FPI ≤ -5) were excluded from the study. Only those with scores within the neutral range (-5 to +5) were enrolled.

We add the following text to the eligibility criteria subsection of the method:

“Foot posture was assessed using the Foot Posture Index (FPI-6), a validated clinical tool that evaluates six criteria of foot alignment and morphology. Each item is scored from -2 to +2, yielding a total score between -12 (highly supinated/pes cavus) and +12 (highly pronated/pes planus). Participants with FPI scores ≥ +6 (flat foot) or ≤ -6 (high arch) were excluded. Only individuals with neutral foot posture (FPI scores between -5 and +5) were included in the study [28].”

-Please provide references for stimulation protocol.

The vibration parameters and schedule in our study were derived from Reference 29 (frequency 30-50 Hz, amplitude 0.5-1 mm) and Reference 14 (20‑minute sessions applied every other day for improving balance and joint position sense).

In manuscript:

“The vibration system delivers perceptible vibration in the frequency range of 30-50 Hz with an amplitude of 0.5-1mm [29], which corresponds to the optimal sensitivity range of fast-adapting afferent nerve fibers involved in proprioception and tactile feedback [14].”

“Those in both groups were asked to activate the vibrotactile system for 20 minutes, three times per week (Saturday, Monday, Wednesday), based on prior evidence indicating optimal neuromuscular adaptation within this dosing regimen and to avoid potential sensory receptor fatigue, habituation, or adverse effects from excessive stimulation [14].”

 

-Why did you include individuals with fracture history or advanced age only to exclude them later (figure 5)?

 

We initially invited 21 volunteers with a history of ankle sprain to participate. Following their acceptance, all individuals underwent an eligibility screening process. Those with a history of fracture or advanced age beyond the defined range were excluded at the eligibility assessment stage, prior to randomization and baseline testing. As shown in Figure 5, these participants were excluded due to the presence of these criteria at the start of the study. In other words, we do not include the participants; we only want to illustrate the complete study process in Figure 5.

 

-Please provide references that let you moderate type 1 and type 2 errors for estimating the sample size.

To justify our approach in moderating Type I (α) and Type II (β) errors during sample size estimation, we have added the following methodological reference:

“40.     O’Neill B. Sample size determination with a pilot study. PLoS One. 2022 Feb 15;17(2):e0262804. https://doi.org/10.1371/journal.pone.0262804.”

 

-The discussion does not support the likely differences of the injured ankle stimulation demands and plantar region.

 

We agree that the discussion section should more address the likely differences between stimulation demands at the injured ankle region and the plantar surface of the foot. The lateral ankle region, around the injured ligaments, requires targeted stimulation because mechanoreceptors in this area are vulnerable to damage during sprains and contribute to impaired afferent input. In contrast, the plantar surface contains a dense distribution of cutaneous mechanoreceptors that continuously interact with ground reaction forces, making it a critical site for proprioceptive feedback and balance control.

To strengthen the discussion, we have now emphasized that ankle-based stimulation may primarily address deficits related to localized ligamentous injury, whereas plantar-based stimulation may provide broader sensory input by enhancing the integration of tactile and proprioceptive cues from the foot-ground interface.

We add the following text to the discussion:

“The differential effects observed between VFO and VAO may be explained by the distinct stimulation demands of the injured ankle region versus the plantar surface. In individuals with FAI, mechanoreceptors around the lateral ankle ligaments are particularly susceptible to injury, reducing localized afferent input [8]. Vibrotactile stimulation at the ankle may therefore target deficits related to ligamentous damage [16]. Conversely, the plantar surface of the foot contains a high density of mechanoreceptors that continuously interact with ground reaction forces, providing rich proprioceptive information for balance and postural control [15,16]. Stimulation at this site may enhance the integration of tactile and proprioceptive cues at the foot-ground interface, thereby producing greater improvements in JPS.”

 

-The sample size is a concern for interpretation of the results, however the term "pilot" make the readers more cautious in generalizing the findings.

We fully agree that the small sample size is a limitation for interpreting the results. However, as noted, the designation of the study as a pilot trial helps readers remain cautious in generalizing the findings. To ensure clarity, we have explicitly mentioned the term pilot in the title of the manuscript, and we have also highlighted this limitation in the final part of the Discussion section under study limitations.

In manuscript:

“This study has several limitations. Firstly, this study's small sample size limits statistical power, although appropriate for an efficacy pilot trial…”

 

 

 

 

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article proposes a novel approach to the management of ankle instability using recent technology (vibrotactile orthoses). The methodology is good, with adherence to the CONSORT 2010 guidelines (please consider citing the most recent CONSORT 2025 update, if applicable) , trial registration, and ethics approval.

Please provide a clear definition of FAI. In recent literature, the term CAI (chronic ankle instability) is more commonly used and more consistently defined. To avoid misunderstandings, the authors should clarify whether they are using FAI as synonymous with CAI, or explicitly describe the differences between these two conditions.

I would ask the authors to (1) specify which potential confounding factors were not measured and/or controlled for, and (2) discuss how this may affect the interpretation of the findings (particularly the VFO vs. VAO comparison on JPS) in the Limitations section. At present, the limitations mention the small sample size and short follow-up, but they do not explicitly address potential confounding or bias.

I encourage the authors to expand the discussion of the potential clinical impact of these findings. In particular, it would be helpful to clarify how the observed between-group differences (VFO vs. VAO) could inform clinical decision-making and the selection of rehabilitation approaches for patients with functional ankle instability (e.g., which patient profiles might benefit more from plantar vs. ankle vibrotactile stimulation, and how these devices could be integrated with established neuromuscular/proprioceptive training). This would strengthen the translational value of the study beyond the experimental outcomes.

 

Author Response

Reply to reviewers

Manuscript: bioengineering-4036402- “The Effects of Ankle versus Plantar Vibrotactile Orthoses on Joint Position Sense and Postural Control in Individuals with Functional Ankle Instability: A Pilot Randomized Trial”

 

Reviewer 2

The article proposes a novel approach to the management of ankle instability using recent technology (vibrotactile orthoses). The methodology is good, with adherence to the CONSORT 2010 guidelines (please consider citing the most recent CONSORT 2025 update, if applicable) , trial registration, and ethics approval.

 

Dear Reviewer,

Thank you very much for reviewing our manuscript and providing us with specific comments. We have included your comments immediately after this letter and responded individually. The comments are in black, and our responses are in blue. The changes made have been highlighted (in yellow) within the manuscript.

With regards,

Corresponding authors

 

Please consider citing the most recent CONSORT 2025 update, if applicable.

We thank the reviewer for this helpful suggestion. We agree that citing the most recent CONSORT 2025 update would strengthen the methodological transparency of our manuscript. We have now reviewed the updated CONSORT guidelines and confirmed their applicability to our study design. Accordingly, we have added a citation to the CONSORT 2025 statement in the Methods section.

 

Please provide a clear definition of FAI. In recent literature, the term CAI (chronic ankle instability) is more commonly used and more consistently defined. To avoid misunderstandings, the authors should clarify whether they are using FAI as synonymous with CAI, or explicitly describe the differences between these two conditions.

We agree that clarification is needed regarding the terminology of FAI and to avoid misunderstandings. FAI refers to the subjective sensation of the ankle giving way during activity, often following a lateral ankle sprain, without necessarily being accompanied by mechanical laxity. It emphasizes deficits in neuromuscular control, proprioception, and sensorimotor function.

 

CAI, on the other hand, is a broader and more consistently defined term in recent literature. It encompasses mechanical instability, such as ligamentous laxity, and functional instability, such as sensorimotor deficits. CAI is generally used to describe recurrent ankle sprains and persistent symptoms lasting more than 12 months.

In our manuscript, we used FAI to specifically highlight the functional deficits, including proprioceptive impairment and balance disturbances, rather than mechanical laxity. However, we acknowledge that CAI is the more widely adopted term in recent literature. We have now explicitly stated that in our study, FAI is used to denote the functional component of CAI, and that participants were screened to exclude those with mechanical instability.

We add the following text to the introduction:

“FAI refers to the subjective sensation of ankle “giving way” and deficits in neuromuscular control following LAS, without necessarily involving mechanical laxity [6]. Chronic Ankle Instability (CAI), as more consistently defined in recent literature, encompasses both mechanical and functional instability [5]. In this study, we use FAI to denote the functional component of CAI, focusing on proprioceptive and balance impairments, while excluding individuals with mechanical instability [7].”

 

I would ask the authors to (1) specify which potential confounding factors were not measured and/or controlled for, and (2) discuss how this may affect the interpretation of the findings (particularly the VFO vs. VAO comparison on JPS) in the Limitations section. At present, the limitations mention the small sample size and short follow-up, but they do not explicitly address potential confounding or bias.

We acknowledge that our limitations section should more explicitly address potential confounding factors and sources of bias. In our study, potentially relevant variables were not measured or controlled for. For example, plantar pressure distribution assessed by foot scanners, which could influence balance and proprioceptive feedback, was not evaluated. Other unmeasured influences include participants’ prior rehabilitation history and daily physical activity levels. With respect to the comparison between VFO and VAO on JPS and balance, these uncontrolled confounders may partly explain variability in the observed effects.

We add the following text to the discussion:

“Our study did not measure or control for potential confounding factors such as plantar pressure distribution assessed by foot scanners, prior rehabilitation history, and daily physical activity levels. These factors may have influenced proprioceptive outcomes and could partly explain variability in the VFO versus VAO comparison on joint position sense.”

I encourage the authors to expand the discussion of the potential clinical impact of these findings. In particular, it would be helpful to clarify how the observed between-group differences (VFO vs. VAO) could inform clinical decision-making and the selection of rehabilitation approaches for patients with functional ankle instability (e.g., which patient profiles might benefit more from plantar vs. ankle vibrotactile stimulation, and how these devices could be integrated with established neuromuscular/proprioceptive training). This would strengthen the translational value of the study beyond the experimental outcomes.

Thank you for this valuable comment, dear reviewer. To strengthen the translational value of our findings, we have added the following text to the discussion:

“The effectiveness of VFO in enhancing JPS indicates that clinicians should focus on improving sensory feedback at the foot-ground interface when treating individuals with FAI. Nevertheless, it is crucial to consider patient classifications: those with additional ligamentous laxity or mechanical instability may benefit from using VAO, which offers both mechanical support and sensory stimulation. Incorporating these devices into rehabilitation protocols requires a structured approach. During the acute recovery phase after recurrent sprains, passive ankle orthoses are the primary intervention [3, 25]. The use of VFO is most suitable during the subacute phase (4-8 weeks post-injury), which focuses on sensorimotor retraining. We recommend starting with daily 20-minute sessions of VFO during weight-bearing activities, gradually advancing to dynamic balance exercises as JPS improves. The VAO can be introduced later in the rehabilitation process when controlled perturbation training begins, utilizing its mechanical stability while also benefiting from vibration-induced neuromuscular facilitation [56].”

 

 

 

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

اكتبه باللغة الانكليزية الرصينة

1. Reporting potential practical issues (such as device bulk, weight, and minor user complaints) in the abstract is crucial for assessing real-world feasibility, a core objective of pilot studies. Its omission creates an overly optimistic impression of the intervention's practicality.
2. The stated objective could be formulated more precisely. For instance: "To compare the immediate and short-term (two-week) effects of vibrotactile stimulation delivered at two distinct anatomical sites on proprioceptive acuity and postural control in individuals with Functional Ankle Instability."
3. The exclusive recruitment of young adults with unilateral FAI severely limits the generalizability of findings. Results cannot be extrapolated to adolescents, older populations, individuals with bilateral instability, or those with comorbidities (e.g., diabetic neuropathy) that alter sensorimotor function.
4. In the Procedures section (2.7), writing out the full names of standardized assessment tools (e.g., Cumberland Ankle Instability Tool - CAIT) upon first mention, rather than only the acronym, would enhance transparency and reader comprehension.
5. The study lacks methodological justification for the specific angular range (±22.5°) and increment (2.5°) chosen for the Joint Position Sense assessment. The anatomical or functional rationale for these parameters is not provided, representing a shortcoming in the description of the measurement instrument.
6. The equations for calculating Center of Pressure velocity, while standard formulas, should be numbered (e.g., Equation 1, 2, 3) for easier reference within the text. Furthermore, merely citing reference [35] without a brief explanation of the formula's origin or significance constitutes a documentation and clarity shortcoming.
7. The purpose of the single-leg stance test on the force plate, as clarified in the text, is to record Ground Reaction Forces and subsequently calculate the trajectory and velocity of the Center of Pressure—a dynamic measure of postural sway and body stability. This justifies the use of this specialized instrument over a simple static scale.
8. Enriching the Introduction or Discussion by noting that Ground Reaction Forces vary substantially with activity level (relatively low in standing, significantly higher in running or jumping) would provide deeper biomechanical context. It highlights that the study tested a relatively low-load condition compared to the high-impact activities often associated with instability.
9. From a vibration engineering perspective, the study treats the vibrotactile stimulus as a simple on/off signal without controlling for or measuring its dynamic properties in situat the anatomical target (e.g., damping, vibration transmission through tissue, local resonant frequencies). This is a significant limitation affecting the consistency of the stimulus and the reproducibility of results.
10. The short intervention duration (two weeks) is insufficient to evaluate long-term neuroadaptive effects or sustainability. The absence of a post-removal follow-up assessment is a major methodological gap, as it prevents distinguishing between a temporary assistive effect and genuine, retained neuroplastic learning.
11. The lack of control or detailed reporting of standardized footwear characteristics (e.g., sole rigidity, ankle support) is a significant potential confounding factor. Footwear can substantially influence ankle-foot mechanics and balance outcomes, thereby reducing measurement accuracy and study replicability.

 

Author Response

Reply to reviewers

Manuscript: bioengineering-4036402- “The Effects of Ankle versus Plantar Vibrotactile Orthoses on Joint Position Sense and Postural Control in Individuals with Functional Ankle Instability: A Pilot Randomized Trial”

 

Reviewer 3

Dear Reviewer,

Thank you very much for reviewing our manuscript and providing us with specific comments. We have included your comments immediately after this letter and responded individually. The comments are in black, and our responses are in blue. The changes made have been highlighted (in yellow) within the manuscript.

With regards,

Corresponding authors

 

Reporting potential practical issues (such as device bulk, weight, and minor user complaints) in the abstract is crucial for assessing real-world feasibility, a core objective of pilot studies. Its omission creates an overly optimistic impression of the intervention's practicality.

We agree that feasibility aspects are important to report in pilot studies. In our manuscript, we had already noted in the Results section that no major practical issues were observed, with only two participants reporting minor discomfort related to the electronic housing bulk during the first week, which was resolved by week two. We have now also added this information to the Abstract.

“Two participants experienced minor discomfort related to the electronic housing bulk in the first week, which was resolved by week two. No further complaints regarding device weight or usability were observed.”

 

The stated objective could be formulated more precisely. For instance: "To compare the immediate and short-term (two-week) effects of vibrotactile stimulation delivered at two distinct anatomical sites on proprioceptive acuity and postural control in individuals with Functional Ankle Instability."

We agree that the stated objective can be formulated more precisely to better reflect the scope and design of our study. Following your recommendation, we have revised the objective statement to emphasize both the time frame (immediate and short-term, two weeks) and the comparative nature of the intervention across anatomical sites.

We have added the following text to the introduction:

“The objective of this pilot study was to compare the immediate and short-term (two-week) effects of vibrotactile stimulation delivered through wearable devices, vibrotactile ankle orthoses (VAO), and vibrotactile foot orthoses (VFO), at two distinct anatomical sites (ankle versus plantar surface) on proprioceptive acuity and postural control in individuals with FAI.”

 

The exclusive recruitment of young adults with unilateral FAI severely limits the generalizability of findings. Results cannot be extrapolated to adolescents, older populations, individuals with bilateral instability, or those with comorbidities (e.g., diabetic neuropathy) that alter sensorimotor function.

Thank you for this suggestion, dear reviewer. We fully agree that the exclusive recruitment of young adults with unilateral FAI limits the generalizability of our findings. As noted in the Limitations section at the end of the Discussion, we have already acknowledged that results cannot be extrapolated to adolescents, older populations, individuals with bilateral instability, or those with comorbidities such as diabetic neuropathy that may alter sensorimotor function. To ensure this point is clear and visible, we have now highlighted this limitation more explicitly in the revised manuscript.

“Finally, the sample consisted exclusively of young adults with unilateral FAI, limiting generalizability to older populations, adolescents, individuals with bilateral instability, or those with comorbidities such as diabetic neuropathy or osteoarthritis, conditions that may alter mechanoreceptor density and central sensorimotor integration.”

 

In the Procedures section (2.7), writing out the full names of standardized assessment tools (e.g., Cumberland Ankle Instability Tool - CAIT) upon first mention, rather than only the acronym, would enhance transparency and reader comprehension.

Thank you for this helpful comment. We have carefully re-checked the manuscript and can now confirm with confidence that all abbreviations are introduced with their full names upon first mention. In addition, at the end of the manuscript, all abbreviations are listed together with their full forms in accordance with the journal’s formatting requirements.

 

The study lacks methodological justification for the specific angular range (±22.5°) and increment (2.5°) chosen for the Joint Position Sense assessment. The anatomical or functional rationale for these parameters is not provided, representing a shortcoming in the description of the measurement instrument.

These parameters were selected based on anatomical and functional considerations as well as precedent in prior proprioception research. The ±22.5° range was chosen to represent a physiologically relevant excursion of ankle inversion/eversion that is large enough to challenge proprioceptive acuity without exceeding safe limits for individuals with FAI. The 2.5° increment was selected to provide a fine resolution for detecting subtle differences in JPS, consistent with thresholds reported in earlier studies of ankle proprioception.

We have added the following text to the method:

“The angular range for JPS testing was set at ±22.5°, representing a physiologically relevant excursion of ankle plantarflexion/dorsiflexion that challenges proprioceptive acuity without exceeding safe limits for individuals with FAI [6]. The increment of 2.5° was selected to provide sufficient resolution for detecting subtle differences in joint position sense, consistent with thresholds reported in prior proprioception studies [31].”

 

The equations for calculating Center of Pressure velocity, while standard formulas, should be numbered (e.g., Equation 1, 2, 3) for easier reference within the text. Furthermore, merely citing reference [35] without a brief explanation of the formula's origin or significance constitutes a documentation and clarity shortcoming.

We thank the reviewer for this constructive comment. According to your suggestion, we have revised the manuscript to improve its quality. We have mentioned the revised text below:

“COP velocity is derived by computing the displacement of the COP over time, essentially the rate of change of CoP position, and has been validated in postural control studies [35]. The anteroposterior (AP) and mediolateral (ML) velocity components [Equations 1,2], along with the resultant COP velocity [Equation 3], were calculated as follows [35]. These velocity-based metrics reflect the temporal dynamics of postural sway and are considered highly sensitive to sensorimotor deficits in FAI [34]:

 

 

 

Where T=30 seconds is the analyzed trial duration.”

 

 

The purpose of the single-leg stance test on the force plate, as clarified in the text, is to record Ground Reaction Forces and subsequently calculate the trajectory and velocity of the Center of Pressure—a dynamic measure of postural sway and body stability. This justifies the use of this specialized instrument over a simple static scale.

Thank you for this valuable comment, dear Reviewer. We would like to clarify that the single-leg stance test is classified as a static postural stability assessment. However, by using a force plate, we are able to derive dynamic parameters (CoP trajectory and velocity), which provide sensitive quantification of sway during static stance. We have revised the text to make this distinction clearer, emphasizing that the test itself is static, but the instrument allows dynamic outcome measures to be obtained. In this regard, while we use the static postural control subsection, we mention that “COP velocity-based metrics reflect the temporal dynamics of postural sway.”

 

Enriching the Introduction or Discussion by noting that Ground Reaction Forces vary substantially with activity level (relatively low in standing, significantly higher in running or jumping) would provide deeper biomechanical context. It highlights that the study tested a relatively low-load condition compared to the high-impact activities often associated with instability.

We agree that highlighting the variability of GRFs across different activity levels can provide valuable biomechanical context. We have added the following text to the discussion section:

“GRF varies significantly with activity level, being relatively low during quiet standing and higher during dynamic tasks such as running or jumping [25]. Accordingly, the present study tested a low-load condition, and future investigations are warranted to examine whether similar benefits of vibrotactile orthoses are observed under high-impact activities commonly associated with ankle instability.”

 

From a vibration engineering perspective, the study treats the vibrotactile stimulus as a simple on/off signal without controlling for or measuring its dynamic properties in situat the anatomical target (e.g., damping, vibration transmission through tissue, local resonant frequencies). This is a significant limitation affecting the consistency of the stimulus and the reproducibility of results.

Thank you for this comment. We have added the following text to the limitation section of the discussion:

“Another limitation of the present study is that the vibrotactile stimulus was treated as a simple on/off signal, without controlling for or measuring its dynamic properties at the anatomical target (e.g., damping, vibration transmission through tissue, local resonant frequencies). Future studies should incorporate vibration engineering analyses to characterize these properties, thereby improving reproducibility and advancing understanding of the mechanisms underlying vibrotactile stimulation.”

The short intervention duration (two weeks) is insufficient to evaluate long-term neuroadaptive effects or sustainability. The absence of a post-removal follow-up assessment is a major methodological gap, as it prevents distinguishing between a temporary assistive effect and genuine, retained neuroplastic learning.

Thank you for this comment. We have added the following text to the limitation section of the discussion:

“Secondly, the intervention duration was brief (two weeks), which may be insufficient to induce meaningful neuroplastic adaptations in dynamic balance or functional mobility. Furthermore, the absence of a post-removal follow-up assessment prevents distinguishing between temporary assistive effects and genuine, retained neuroplastic learning. Future studies should therefore adopt longer intervention periods and include follow-up assessments to clarify the durability of observed improvements.”

 

The lack of control or detailed reporting of standardized footwear characteristics (e.g., sole rigidity, ankle support) is a significant potential confounding factor. Footwear can substantially influence ankle-foot mechanics and balance outcomes, thereby reducing measurement accuracy and study replicability.

We thank the reviewer for raising this important point. We agree that footwear characteristics can substantially influence ankle–foot mechanics and balance outcomes, and therefore require clear reporting to avoid confounding. As noted in the Procedures section, we had already specified that all participants used the interventions while wearing low‑cut athletic shoes with flat, in‑sole‑free interiors. This standardized footwear condition was chosen to minimize variability in ankle support and sole rigidity across participants.

In addition, we have now clarified that athletic shoes typically provide comparable and sufficient sole rigidity, which further supports the consistency of testing conditions and reduces potential confounding effects.

“All participants used the interventions while wearing low‑cut athletic shoes with flat, in‑sole‑free interiors. Athletic shoes typically provide a similar and sufficient sole rigidity, which helps standardize ankle-foot mechanics across participants.”

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

We would like to sincerely thank you for carefully addressing the majority of the reviewers’ comments and for the revisions undertaken, which have clearly improved the quality of the manuscript. As a minor additional suggestion, it is recommended to revise Figure 6 by presenting the results using a bar chart, as this format is more appropriate given the noticeable fluctuations in the data. The intermediate points may exhibit distinct behavior, and therefore a linear representation could lead to a less reliable interpretation of the overall trend.

Author Response

Manuscript: bioengineering-4036402- “The Effects of Ankle versus Plantar Vibrotactile Orthoses on Joint Position Sense and Postural Control in Individuals with Functional Ankle Instability: A Pilot Randomized Trial”

 

Reviewers’ comments:

We would like to sincerely thank you for carefully addressing the majority of the reviewers’ comments and for the revisions undertaken, which have clearly improved the quality of the manuscript. As a minor additional suggestion, it is recommended to revise Figure 6 by presenting the results using a bar chart, as this format is more appropriate given the noticeable fluctuations in the data. The intermediate points may exhibit distinct behavior, and therefore a linear representation could lead to a less reliable interpretation of the overall trend.

 

Response:

We sincerely thank you for your comment regarding the presentation of Figure 6. In accordance with your recommendation, Figure 6 has been fully revised and is now presented as a bar chart, which more appropriately represents the discrete time points (T1, T2, and T3) and avoids implying any misleading linear trends, particularly given the fluctuations at the intermediate assessment point. Additionally, the figure caption has been rewritten to accurately describe the new visualization and to explicitly clarify the rationale for using bar charts. 

Author Response File: Author Response.pdf