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Influence of Body Weight Support Systems on the Abnormal Gait Kinematic

Appl. Sci. 2020, 10(13), 4685; https://doi.org/10.3390/app10134685

by Van-Thuc Tran^1,2,*,†

, Kota Sasaki^1,† and Shin-ichiroh Yamamoto^1,†

Reviewer 1: Anonymous

Reviewer 2: Anonymous

Reviewer 3: Anonymous

Appl. Sci. 2020, 10(13), 4685; https://doi.org/10.3390/app10134685

Submission received: 9 June 2020 / Revised: 1 July 2020 / Accepted: 4 July 2020 / Published: 7 July 2020

(This article belongs to the Section Applied Biosciences and Bioengineering)

Round 1

Reviewer 1 Report

This paper investigated the effects of two body weight support systems: the active body weight support system and the counter weight system, on an abnormal gait.

line 132, were developed to the COM (consider revision)

line 344, that the potential and high performance (consider revision)

The study does support the initial hypothesis anticipating that the ABWS system improves the gait characteristics and provides better behavior in comparison with the CW system in most cases such as maximum displacements of the horizontal COM and mean COP.

Maybe adding some explanation of the unloading force of the ABWS system would help readers understand it better.

Author Response

Reviewer Comments

This paper investigated the effects of two body weight support systems: the active body weight support system and the counter weight system, on an abnormal gait.

line 132, were developed to the COM (consider revision)

line 344, that the potential and high performance (consider revision)

Maybe adding some explanation of the unloading force of the ABWS system would help readers understand it better.

Authors Response

Comment 1.1: This paper investigated the effects of two body weight support systems: the active body weight support system and the counter weight system, on an abnormal gait.

Response 1.1: We would like to thank the reviewer for the comment. Yes, our main purpose is to investigate the influence of the unmodulated BWS system based on the Counter Weight system and modulated BWS system power by the Pneumatic Muscle Actuator (called active Body Weight Support system) on the abnormal gait during walking on the treadmill. The abnormal gait was generated by a healthy subject walking on the treadmill; however, the knee motion on one side was restricted.

Comment 1.2: line 132, were developed to the COM (consider revision).

Response 1.2: line 132, we corrected the grammar error, the revised text is given below:

The MATLAB (The MathWorks, Inc., Natick, MA, USA ) routines were developed to calculate the COM and the margin of stability (MOS), and the COP.

Comment 1.3: line 344, that the potential and high performance (consider revision)

Response 1.3: we corrected the grammar error, revised text (line 346 in the revised manuscript) is given below:

Nevertheless, the improvement of the gait patterns and kinematic parameters of the abnormal walking under the ABWS system suggested the potential implementation and the high performance of the modulated active BWS system in clinical practice.

Comment 1.4: The study does support the initial hypothesis anticipating that the ABWS system improves the gait characteristics and provides better behavior in comparison with the CW system in most cases such as maximum displacements of the horizontal COM and mean COP.

Maybe adding some explanation of the unloading force of the ABWS system would help readers understand it better.

Response 1.4: We appreciate your kind suggestion. In this present study, the authors gave a brief explanation of the unloading force of the ABWS system in the first paragraph of subsection 2.1. Apparatus (line 79-90). The detail of the control strategy and the unloading force can be found in the previous study, which was also mentioned in this paragraph:

Van Thuc, Tran, and Shin-ichiroh Yamamoto. Development of a Body Weight Support System Using Pneumatic Muscle Actuators: Controlling and Validation. Advances in Mechanical Engineering, 8(12), 2016. doi:10.1177/1687814016683598

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is interest and presents coerents experimental results. Like the authors said: "Therefore, the contribution of the BWS system on
gait rehabilitation as an intervention in clinical is still unclear and needs further investigation"

But the paper need some corrections to increase the quality of that.

"The results confirmed the applicability of two Body Weight Support systems in clinical practice as a recovered gait intervention." This is not true until trial test with patients.

Is recommended cite at introduction others kinds of BWS like:

MIT-Skywalker: considerations on the Design of a Body Weight Support System. J NeuroEngineering Rehabil 14, 88 (2017). https://doi.org/10.1186/s12984-017-0302-6

- Cite BWS commercial devices like ZeroG, etc..

"Figure 2, subjects reproduced the gait pattern like hemiplegia, and this walking condition was called as abnormal walking." This is true? Need give some reference or compare the results with other papers that presents results of hemiplegic gait

"unloading force level at 30, 50, and 70% of the subject weight". Why this values?

"and kept steadily at 2 km/h." Why this speed? Is not high to hemiplegic patient?

"was approved by the ethical committee of the Shibaura Institute" Please, inform the number

"..would be like a pretend hemiplegic patient at a very early stage..." Need to prove or give reference/compare.

Need to add in future works test with patients.

other corrections:

"Americans 20 20 years"

Author Response

Reviewer Comments

The paper is interest and presents coerents experimental results. Like the authors said: "Therefore, the contribution of the BWS system on gait rehabilitation as an intervention in clinical is still unclear and needs further investigation"

But the paper need some corrections to increase the quality of that.

"The results confirmed the applicability of two Body Weight Support systems in clinical practice as a recovered gait intervention." This is not true until trial test with patients.

Is recommended cite at introduction others kinds of BWS like:

MIT-Skywalker: considerations on the Design of a Body Weight Support System. J NeuroEngineering Rehabil 14, 88 (2017). https://doi.org/10.1186/s12984-017-0302-6

- Cite BWS commercial devices like ZeroG, etc..

"unloading force level at 30, 50, and 70% of the subject weight". Why this values?

"and kept steadily at 2 km/h." Why this speed? Is not high to hemiplegic patient?

"was approved by the ethical committee of the Shibaura Institute" Please, inform the number

"..would be like a pretend hemiplegic patient at a very early stage..." Need to prove or give reference/compare.

Need to add in future works test with patients.

other corrections:

"Americans 20 20 years"

Authors Response

Comment 2.1: The paper is interest and presents coerents experimental results. Like the authors said: "Therefore, the contribution of the BWS system on gait rehabilitation as an intervention in clinical is still unclear and needs further investigation"

But the paper need some corrections to increase the quality of that.

"The results confirmed the applicability of two Body Weight Support systems in clinical practice as a recovered gait intervention." This is not true until trial test with patients.

Response 2.1: We appreciate your comments. We agree with the reviewer’s comment that the confirmation can be stated only until the trial implements on patients. However, the good behavior of the two Body Weight support system on abnormal gait could suggest their applicability to clinical practice as an intervention. The statement in the abstract (line 13 in the revised manuscript) was modified as below:

The results suggested the applicability of two Body Weight Support systems in clinical practice as a recovered gait intervention.

Comment 2.2: Is recommended cite at introduction others kinds of BWS like:

MIT-Skywalker: considerations on the Design of a Body Weight Support System. J NeuroEngineering Rehabil 14, 88 (2017). https://doi.org/10.1186/s12984-017-0302-6

- Cite BWS commercial devices like ZeroG, etc..

Response 2.2: Thank you for your suggestion. However, the MIT-Skywalker is a specific Body Weight system which includes a bicycle seat. Therefore, it can be classified as a seat-type Body Weight Support system which differs from the hanging-type, objectives of this study. The authors excluded it from our references.

The BWS commercial devices like ZeroG are mostly similar to the device developed by Sousa CO, et.al. which was mentioned in this study.

Comment 2.3: "Figure 2, subjects reproduced the gait pattern like hemiplegia, and this walking condition was called as abnormal walking." This is true? Need give some reference or compare the results with other papers that presents results of hemiplegic gait.

Response 2.3: Thank you for your comments. The abnormal gait was generated by a healthy subject walking on the treadmill with two constraints: knee joint motion restricted and the 3kg-load on the ankle joint. Figure 2 showed the devices and how we installed them on the subject’s leg. From our observation, the posture and gait patterns of subjects were very similar to the hemiplegia. Furthermore, in the range of motion subsection, the hip, knee and the ankle angle of the abnormal showed the behavior agree with the previous studies such as:

Winters, T. F., J. R. Gage, and R. Hicks. Gait patterns in spastic hemiplegia in children and young adults. J Bone Joint Surg Am 69.3 (1987): 437-441.

Olney, Sandra J., Malcolm P. Griffin, and Ian D. McBride. Temporal, kinematic, and kinetic variables related to gait speed in subjects with hemiplegia: a regression approach. Physical therapy 74.9 (1994): 872-885.

Olney, Sandra J., and Carol Richards. Hemiparetic gait following stroke. Part I: Characteristics. Gait & posture 4.2 (1996): 136-148.

The authors added some text mentions about the analog of the abnormal walking to the hemiparetic gait in the fourth paragraph of the discussion section. The above references were also included. The text added from line 307 to 309 as below:

In Figure 9, the ranges of motion of the abnormal walking condition showed the analog shapes of the gait pattern of hemiplegia which was reported in previous studies [50–52].

Comment 2.4: "unloading force level at 30, 50, and 70% of the subject weight". Why this values?

Response 2.4: Thank you for your question. The final goal is to clarify the contribution of the BWS system on gait rehabilitation as an intervention in clinical. As mentioned in the final paragraph of the present study, Jørgensen HS et al. indicated that the recovery of walking function mainly occurs within the first 11 weeks after stroke. Therefore, the gait rehabilitation should be implemented as soon as possible to get a better recovery of walking function. In that case, the high unloading level (might up to 70% unloading force) could be implemented to help the patients carry their weight at the stage of the gait training. The unloading level could gradually reduce base on the improvement of the walking function. From the above reasons, the authors decided to implement the experiment at three unloading levels: low level (30%), middle level (50%), and high level (70%).

Comment 2.5: "and kept steadily at 2 km/h." Why this speed? Is not high to hemiplegic patient?

Response 2.5: Thank you for your question. For the healthy subject, the walking speed can be much twice higher than 2 km/h (up to 5 km/h). The walking speed of the hemiplegic patient can be varied and would be sometimes higher than 2km/h. This result can be found in:

Witte US, Carlsson JY. Self-selected walking speed in patients with hemiparesis after stroke. Scand J Rehabil Med. 1997;29(3):161-165.

Roth, Elliot; Merbitz, Charles; Mroczek, Kenneth; Dugan, Sheila; Suh, W. HEMIPLEGIC GAIT: Relationships Between Walking Speed and Other Temporal Parameters1, American Journal of Physical Medicine & Rehabilitation: March-April 1997 - Volume 76 - Issue 2 - p 128-133.

The authors selected the treadmill speed at 2km/h because this speed is a reasonable walking speed of hemiplegia.

Comment 2.6: "was approved by the ethical committee of the Shibaura Institute" Please, inform the number

Response 2.6: Thank you for your comment. Currently, the approval procedure in our Institute has not come out with the number, so we don’t have the number now.

Comment 2.7: "..would be like a pretend hemiplegic patient at a very early stage..." Need to prove or give reference/compare.

Response 2.7: Thank you for your comment. As mentioned in the Response 2.3, the posture and gait patterns of subjects while walking with knee joint restriction and 3kg-load on the ankle joint were similar to the hemiplegia. The statement mentions the abnormal walking would be like a pretend hemiplegic patient at a very early stage since the gait patterns such as knee and ankle angles were much distorted. For a summary statement of the conclusion, the sentence was modified as below (line 350 in the revised manuscript):

In this research, the abnormal gait, which was generated by the restricted knee joint movement and 3kg-weight on ankle joint, would be like a pretend hemiplegic patient.

Comment 2.8: Need to add in future works test with patients.

Response 2.8: Thank you for your suggestion. Authors modified the last statement of the conclusion as below (line 358-360):

Furthermore, implementation of the ABWS and CW system on patients such as hemiplegia, patients after spinal cord injury will be considered to observe the changes of the gait parameters and improve the ambulation functionality of patients.

Comment 2.9: other corrections:

"Americans 20 20 years"

Response 2.9: Thank you for your comment. We corrected the grammar error; the revised text is given below (line 23-25):

Also, a report from the American Heart Association showed that an estimated 7.0 million Americans ≥ 20 years of age had a stroke [8].

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper compared the effect of the active body weight support system to passive body weight support system on gait parameters including center of mass, center of pressure, margin of stability, and step parameters with healthy subject walking on the treadmill with constraint knee motion. Overall the paper was detailed presented and the potential clinical impact was recognized.

Here are some concerns and comments:

1) While the major reason for the study was that previous studies were studied based on implementation of healthy subjects, this study was also based on healthy subjects. The assumption of their gait performances would simulate patients with hemiplegia were not sufficiently justified. If preliminary data existed for this assumption, they should be included. If not, at least the gait performances of the constraint knee motion should compare to those reported in literature. Such as:

Sandra J Olney, Malcolm P Griffin, Ian D McBride, Temporal, Kinematic, and Kinetic Variables Related to Gait Speed in Subjects With Hemiplegia: A Regression Approach, Physical Therapy, Volume 74, Issue 9, 1 September 1994, Pages 872–885, https://doi.org/10.1093/ptj/74.9.872

George Chen, Carolynn Patten, Dhara H. Kothari, Felix E. Zajac, Gait differences between individuals with post-stroke hemiparesis and non-disabled controls at matched speeds, Gait & Posture, Volume 22, Issue 1,
2005, Pages 51-56, ISSN 0966-6362, https://doi.org/10.1016/j.gaitpost.2004.06.009.

2) Some important literature were not included which studying the influence of BWS system on gait parameters for patients, such as

Mehrholz J, Thomas S, Elsner B. Treadmill training and body weight support for walking after stroke. Cochrane Database Syst Rev. 2017 Aug 17;8:CD002840. doi: 10.1002/14651858.CD002840.pub4. Review. PubMed PMID: 28815562; PubMed Central PMCID: PMC6483714.

Drużbicki M, Przysada G, Guzik A, Brzozowska-Magoń A, Kołodziej K, Wolan-Nieroda A, Majewska J, Kwolek A. The Efficacy of Gait Training Using a Body Weight Support Treadmill and Visual Biofeedback in Patients with Subacute Stroke: A Randomized Controlled Trial. Biomed Res Int. 2018;2018:3812602. doi: 10.1155/2018/3812602. eCollection 2018. PubMed PMID: 29850509; PubMed Central PMCID: PMC5907400.

3) It seemed the order for participants experiencing the two body weight support system was not randomized. The potential learning effect should be discussed.

4) The results were very detailed presented but somewhat difficult to follow as there are too many figures. Some of the figures can be presented in tables which might be easier to follow, such as Figure 10.

5) While it was excited to report the statistically significant findings, 95% confidence interval might be more meaningful with both statistical significance, and clinical indications. I recommend to report the 95% confidence intervals of the gait parameters on normal, abnormal and the two BWS system.

6) The first paragraph of the introduction was not tightly connected with the paper as it was not gait relevant.

7) There are some grammar errors.

Author Response

Reviewer Comments

Here are some concerns and comments:

Sandra J Olney, Malcolm P Griffin, Ian D McBride, Temporal, Kinematic, and Kinetic Variables Related to Gait Speed in Subjects With Hemiplegia: A Regression Approach, Physical Therapy, Volume 74, Issue 9, 1 September 1994, Pages 872–885, https://doi.org/10.1093/ptj/74.9.872

2) Some important literature were not included which studying the influence of BWS system on gait parameters for patients, such as

3) It seemed the order for participants experiencing the two body weight support system was not randomized. The potential learning effect should be discussed.

6) The first paragraph of the introduction was not tightly connected with the paper as it was not gait relevant.

7) There are some grammar errors.

Authors Response

Comment 3.1: While the major reason for the study was that previous studies were studied based on implementation of healthy subjects, this study was also based on healthy subjects. The assumption of their gait performances would simulate patients with hemiplegia were not sufficiently justified. If preliminary data existed for this assumption, they should be included. If not, at least the gait performances of the constraint knee motion should compare to those reported in literature. Such as:

Response 3.1: We appreciate your comments. As mentioned in the fourth paragraph of the introduction, our motivation is to investigate the changes in the gait parameters of the abnormal walking under the Body Weight Support system. The abnormal gait was generated by a healthy subject walking on the treadmill with two constraints: knee joint motion restricted and the 3kg-load on the ankle joint. Previous studies investigated the influence of the BWS system on gait parameters of healthy subjects, however, the subject walked without any restriction of the knee and ankle joint motion. This point means that the results just presented how the normal gait parameters of the healthy subject changed while walking under the BWS system. The consideration of changes in the abnormal gait under the Body Weight Support system is the main different point from the previous studies. In our opinion, if we would like to consider the Body Weight Support system as an intervention, the investigation of the influence of the Body Weight Support system on the abnormal walking like hemiplegia is necessary.

From our observation, the posture and gait patterns of the abnormal walking condition were very similar to the hemiplegia. Furthermore, in the range of motion subsection, the hip, knee and the ankle angle of the abnormal showed the behavior agree with the previous studies such as:

Winters, T. F., J. R. Gage, and R. Hicks. Gait patterns in spastic hemiplegia in children and young adults. J Bone Joint Surg Am 69.3 (1987): 437-441.

Olney, Sandra J., and Carol Richards. Hemiparetic gait following stroke. Part I: Characteristics. Gait & posture 4.2 (1996): 136-148.

In Figure 9, the ranges of motion of the abnormal walking condition showed the analog shapes of the gait pattern of hemiplegia which was reported in previous studies [50–52].

This reference was included in the revised manuscript (the fourth paragraph of the discussion section, from line 307 to 309).

This study mainly considered walking speed and temporal parameters. Future works, we will also investigate the changes in the temporal parameters. However, in this study, this reference was excluded.

George Chen, Carolynn Patten, Dhara H. Kothari, Felix E. Zajac, Gait differences between individuals with post-stroke hemiparesis and non-disabled controls at matched speeds, Gait & Posture, Volume 22, Issue 1, 2005, Pages 51-56, ISSN 0966-6362, https://doi.org/10.1016/j.gaitpost.2004.06.009

this paper considered kinetic energy consumption. We will also investigate the kinetic energy in future work. In this study, this reference was excluded.

Comment 3.2: Some important literature were not included which studying the influence of BWS system on gait parameters for patients, such as

Response 3.2: Thank you for your suggestion. From the literature, we could find hundreds of papers studying the influence of the Body Weight Support system on gait parameters for both patients and healthy subjects. Authors only selected papers mostly related to the objective of the present study. Regarding your suggestions:

This review paper also mentioned our selected references and mainly focus on the walking speed outcome which differs from our consideration. Therefore, this literature was excluded from our references.

This paper considered the visual Biofeedback which differs from our consideration. We excluded it from the manuscript.

Comment 3.3: It seemed the order for participants experiencing the two body weight support system was not randomized. The potential learning effect should be discussed.

Response 3.3: Thank you for your comment. Authors agree that the order for participants experiencing the two Body Weight Support systems was not randomized and the potential learning would happen. However, in our opinion, the motor learning effect would be not significant, because the subject had practice time for familiar with the walking condition. Future work, further analysis will investigate the motor learning effect.

Comment 3.4: The results were very detailed presented but somewhat difficult to follow as there are too many figures. Some of the figures can be presented in tables which might be easier to follow, such as Figure 10.

Response 3.4: Thank you for your suggestion. Figure 10 was replaced by the Table in the revised manuscript, please see on the subsection “3.5. The stride length, step width, and step length”.

Comment 3.5: While it was excited to report the statistically significant findings, 95% confidence interval might be more meaningful with both statistical significance, and clinical indications. I recommend to report the 95% confidence intervals of the gait parameters on normal, abnormal and the two BWS system.

Response 3.5: Thank you for your suggestion. In this present study, the one-way analysis of variance (ANOVA) on ranks method was used to investigate the differences. Therefore the 95% confidence intervals from the post-hoc analysis were also indicated on ranks. In our opinion, the 95% confidence intervals would make the audience a bit of confusion in that case. The p-value is clear, and the audience could easier focus on the changes in the gait pattern and parameters.

Comment 3.6: The first paragraph of the introduction was not tightly connected with the paper as it was not gait relevant.

Response 3.6: Thank you for your comment. In the first paragraph, we would like to point out the situation of patients with hemiplegia, and therefore, the necessity of rehabilitation methods for walking recovery. We believe that the audience after understanding the situation of hemiplegic patients could recognize the important role of the gait rehabilitation and the Body Weight Support system.

Comment 3.7: There are some grammar errors.

Response 3.7: Thank you for your comment. We corrected some grammar errors as below:

line 13: The results suggested the applicability of two Body Weight Support systems in clinical practice as a recovered gait intervention.

lines 23-25: Also, a report from the American Heart Association showed that an estimated 7.0 million Americans ≥ 20 years of age had a stroke [8].

line 132: The MATLAB (The MathWorks, Inc., Natick, MA, USA ) routines were developed to calculate the COM and the margin of stability (MOS), and the COP.

Line 346: Nevertheless, the improvement of the gait patterns and kinematic parameters of the abnormal walking under the ABWS system suggested the potential implementation and the high performance of the modulated active BWS system in clinical practice.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Thank you for addressing the comments.

1) for the concern of how close the simulated abnormal gait performance could be compared to real patients, there was nothing explained in the revised article. It is suggested to included response to the comments in the revised article. In addition, in your response you mentioned " From our observation, the posture and gait patterns of subjects were very similar to the hemiplegia.", will you be able to quantify the similarity? How about patients with other conditions such as SCI?

2) It is fine to include only p value, but can you please describe the magnitude of the changes on gait performance, were they clinically meaningful?

Author Response

We appreciate your valuable comments and suggestions. We would like to respond to your questions below:

Reviewer Comments

Thank you for addressing the comments.

2) It is fine to include only p value, but can you please describe the magnitude of the changes on gait performance, were they clinically meaningful?

Authors Response

Comment 1: for the concern of how close the simulated abnormal gait performance could be compared to real patients, there was nothing explained in the revised article. It is suggested to included response to the comments in the revised article. In addition, in your response you mentioned " From our observation, the posture and gait patterns of subjects were very similar to the hemiplegia.", will you be able to quantify the similarity? How about patients with other conditions such as SCI?

Response 1: Thank you for your suggestion. Firstly, authors are aware that the lack of comparison between the abnormal gait and the patient’s gait is one of the drawbacks of this manuscript. Due to the experiment did not conduct on the real patient, then it is difficult to quantify how similarity of the abnormal gait to the real patient gait. In future work, we will conduct experiments with real patients and analyze the correlation between the abnormal gait generated on the healthy person and the gait on the real patient. In the present study, we do not want to go deep on the analysis of the similarity between them rather than focusing on the influence of the BWS system on the abnormal gait. Secondly, our objective is the consideration of the changes in the abnormal gait which is a general case that could be hemiplegia or SCI patient. The hemiplegia is just a specific example of the abnormal gait that could be similar. As mentioned, we do not want to go deep on the analysis of the abnormal gait and how it could be similar to the gait performance of hemiplegia or SCI patient.

A simple comparison with previous studies of the revised manuscript was added in the 4^thparagraph of the discussion section (line 307 - 312):

In Figure 9, the lost peak can be seen in the range of motion of the knee joint for the abnormal walking condition and abnormal walking under both the ABWS and CW system at all unloading weight supported levels. The ankle angle patterns of all abnormal walking conditions were distorted and differed from the normal walking condition. The ranges of motion of the abnormal walking condition showed the analog shapes of the gait pattern of hemiplegia which was reported in previous studies [50-52]. These results suggested that the successful reproduction of the gait pattern like hemiplegia of the abnormal walking condition.

Comment 2: It is fine to include only p value, but can you please describe the magnitude of the changes on gait performance, were they clinically meaningful?

Response 2: Thank you for your comment. In this study, we focused on the changes of the gait performance under the Counter Weight system and the modulated active Body Weight Support system which was applied a specific control strategy for the unloading force. In that case, we believe that analyzing the change in gait performance would be more meaningful in clinical practice. In our opinion, analyzing the magnitude of the changes in gait performance would be meaningful when we want to apply the active Body Weight Support system for gait-driven or improvement of the unloading force control strategy.

Author Response File: Author Response.pdf

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