Dynamic Measures of Balance during a 90° Turn in Self-Selected Gait in Individuals with Mild Parkinson’s Disease

Round 1

Reviewer 1 Report

Thanks very much to share your valuable research. All sections were written very well.

Goodluck

Author Response

Thank you for your review and affirmation.

Reviewer 2 Report

In this manuscript, the authors examine dynamic balance control in individuals with mild to moderate PD and healthy individuals during walking while performing 90-degree turns. This project is quite interesting. 

 

Minor questions

1.     It better to make it clearer the main purpose for doing this project both in  Abstract and Conclusion sections. 

2.     The ratio of M:F is quite high both in PD and CON, could the author explain how they chose the participants?

Author Response

1. We have revised the purpose statement in the abstract to be consistent in the abstract, the body of the manuscript, and the conclusion.
2. Participants for this project were recruited from the local community (as described in the method section) and were simply a sample of convenience. Therefore, we had no control over the ratio of female/male participants. We have identified this as a limitation of our method.

Reviewer 3 Report

Thank you for submitting this highly comple piece of work. I can appreciate the time you have spent in setting this up and collecting and analyzing the data. I have made numerous comments and suggestions throughout the paper which require your attention.

Comments for author File: Comments.pdf

Author Response

1. Title: suggested word changes were incorporated.
2. Introduction:

• Revised lines 30-31.
• Revised lines 43-45.
• Revised lines 64-68 and added a figure to illustrate the inverted pendulum model.
• Relative to comment related to lines 86-94 – please see Figure 4 in methods for an explanation of the MOS variables.
• Added references to the statement in line 96.
• Relative to comments made on line 103: we provided a reasonable rationale for our situation related to not performing the assessment you referred. One of our authors is certified in these assessments, consulted with our student researchers about this issue, and was satisfied that the project could move forward with this limitation. In our opinion, not performing this assessment does not detract from the contributions of our work. In addition, an assessment of balance abilities (Berg Balance Scale) and a Functional Gait Screen were conducted as part of the inclusion/exclusion criteria (refer to Table 1). These inclusion criteria ensured that participants in this study were community ambulators without an assistive device and without high fall risk; therefore, we can confidently describe the sample as having mild to moderate Parkinson’s disease.
• Relative to comment and query on lines 184-185: much of the research was performed by graduate students and due to time constraints we divided the work into separate projects and, thus, papers.

3. Methods: with regard to the detail in the methods section. We believe that the reader needs sufficient detail to enable them to replicate our work and will not move any of the information to a supplementary section, which would create a disjoint in what we did. Furthermore, for this special topic publication, we believe that we are not under page limits (to a reasonable degree).
4. Results: there were several sections that we felt were not strongly relevant to our primary purpose and deleted them.
5. Discussion:

• Revised the phrase “trend toward a meaningful difference” to “marginally significant differences”, with the rationale for the use of that phrase provided in the Data Analysis section of Methods.
• Deleted lines 529-534, as suggested.

6. References: checked and revised references to meet journal format style.

Reviewer 4 Report

Thank you for submitting this paper to Applied Sciences. The manuscript under consideration: "Dynamic Measures of Balance with a 90-degree Turn during Self-selected Gait in Individuals with Mild Parkinson’s Disease" is an interesting article on an important topic in Applied Sciences. However, there are a few major concerns.

 

1. The introduction is redundant. How about summarizing and shortening the points a little more?

 

2. In the study 11 patients and control 10 participated. How did the authors determine the sample appropriate size? Why not power calculations performed a priori? Please provide all parameters for the sample size calculation in the Methods.

 

3.  Please clarify a clear reason why PD in the medicated state was targeted. It is important to evaluate the patient in the unmedicated state because the medicated state will affect the results of this study.

 

4.  Please show the detailed flow of the study enrollment. The number of PD invited to participate and the number of PD who actually agreed to participate are required. The detailed method of invitation must also be described.

 

5. "The PIG model was modified by placing markers on the head of the 5th metatarsals. The PIG model marker location modifications also included thigh marker placement on the mid-lateral thigh and tibial markers on the mid-lateral shank. Wands were not used for thigh and tibial markers. See the Appendix for a list of markers, marker abbreviations, and placement descriptions." Please provide evidence of the reliability and validity of this measurement method.

 

6.  I have concerns about the method of statistical analysis. Two-factor mixed-model ANOVAh does not seem appropriate with this small sample. Are all the data normally distributed?

 

7. Too many research limitations. This makes one wonder if this research study is really worthwhile.

Author Response

1. We agree and will make appropriate changes to make the introduction more concise.
2. We did not perform an a priori power analysis because we saw this project as exploratory, and our institutional IRB did not require a power analysis for exploratory-type research. As noted in the methods section, the sample size was not predetermined but was constrained by sampling by convenience. All inclusion and exclusion criteria are provided in Table 1 in the Methods section.
3. Individuals with PD are medically managed to be able to function for daily tasks and mobility in their optimally medicated state. The medication schedule prescribed by Movement Specialist Neurologists attempts to minimize "off times" in their PD medications so that the individual's movement and balance function is at its best. Therefore, it is reasonable to assess walking with turns during the "on state" of their medications.
4. We have added a flow diagram of the study enrollment. Detailed methods of recruitment are provided in the Methods section.
5. We provided more detail in the Appendix regarding our use of alternative marker placements at the knee and ankle. Moreover, we also now provide references on the validity and reliability of the PIG kinematic model in the Appendix. Note: since our participants were tested in a single session, repeatability is not an essential issue.

Use of the 5^th metatarsal markers was not used for kinematic determination of joint angles, but only to identify the location of the lateral margin of base of support. This is a common practice by those also using MOS metrics, none of which referred to any validation for the use of foot markers to establish base of support boundaries (see references below:

• Kazsanski ME et al. J. Biomech. 2022,144:111334;
• Lufade V, Kaufman K. Gait Posture. 2014,40:252-254;
• Hak L, et al. PLoS ONE. 8(12):e82842;
• McAndrew Young PM, et al. J. Biomech. 2012,45:1053-1059.

6. Choosing a mixed model including subject as a random effect as well as nesting limb within subject helps to control for subject-to-subject and limb-to-limb variation that can blur the effect of condition (Parkinson’s versus Control). Adding these significant factors has the effect of increasing the power of the primary test on condition by reducing variation extraneous to the primary focus of the study, similar to the advantage of using a paired t-test or an ANCOVA to remove subject variation. The more complete model also reduces some of the potential non-normality that will show up without these factors in the model. Residual analysis shows good normality and constant variance across the board.
7. We believe it important to briefly review how subsequent research on the use of the MOS metrics might, or need to, be revised, relative to Hof et al.’s original work; however, rather than cite this work as a limitation of our project we suggested that future research using alternative models of MOS should be considered. We also reduced the study limitation section to reflect just the most notable limitations in study design.

Round 2

Reviewer 3 Report

I thank the authors for addressing all my comments and adding the extra figure for clarification.

My only remaining request is that you rewrite the sentence in line 521-522 - I feel it does not read well.

Author Response

Thank you for your suggestion. We have rewritten those lines as: 

"The traditional classification of disease severity in PD, i.e., Hoehn & Yahr staging, the Unified Parkinson’s Disease Rating Scale was not used in this study to categorize the participants due to the researchers’ limitations in training and formal certification in the administration and scoring of these standardized measures. However, given that the PD participants’ balance and gait function was assessed using standard methods accepted by the clinical community their description as having mild to moderate PD is accurate and reasonable."

Author Response File: Author Response.pdf

Reviewer 4 Report

The authors made necessary revisions.

Author Response

Thank you for your critical review.