Investigation of the Correlation between Factors Influencing the Spectrum of Center of Pressure Measurements Using Dynamic Controlled Models of the Upright Stand and Subject Measurements
Round 1
Reviewer 1 Report
On line 191(table 2), the authors must replace the word "condiotion" in the table with "condition".
Author Response
thank you very much for the advice. we have taken it.
Reviewer 2 Report
This manuscript appears to have been previously revised; therefore, several questions have been answered in the current version.
However, I think there are some issues that need to be modified for possible publication of the manuscript.
Title: I think it is very long and somewhat confusing. Also, "back pain" should appear on it.
Introduction: There are numerous errors in reference numbers
when they are continuous. For example, line 33: [1,2,3]. According to the instructions for the authors, they should be indicated as [1-3].
The same situation in line 38: [4,5,6,7,8,9], should be: [4-9]. Please refer to the instructions for authors https://www.mdpi.com/journal/applsci/instructions
and check the references throughout the manuscript.
Material and methods: lines 150-151. Could they have affected the sequence set in the results obtained? Could not a randomized sequence have been better so that there were no effects of fatigue and / or learning / training of the participants?
Please indicate this in the discussion or study limitations.
Data Analysis: A more in-depth description of the statistical analyzes carried out is necessary, indicating the objective of each analysis. For example, describe the ANOVA. And so with all the analyzes carried out.
Results: Line 191. “Overview” must start with a capital letter.
Table 2. There are dots (.) between the words instead of bar space.
Line 193. Table “two” is better at number 2.
Line 203. “figure” must start in a capital letter: Figure
Line 204: “table” must start in a capital letter: Table
Table 4. Table 2. There are dots (.) between the words instead of bar space.
References, Please check all references, there are some errors. For example, in several of them, No. appears According to the instructions, this should not be For example, in the references, 4, 6, 31, 32, 33, ...
Add a space between Gait & Posture in all the references of this magazine. For example, references #: 9, 19, 33, ...
The words of the title of the reference nº36 are in capital letters.
Reference nº 41, there is a double dot ".."
Reference numbers 44 and 46, the pages are missing.
References nº53, 54, and 55, the year is missing.
Author Response
First of all we would like to thank you for the constructive hints that helped to improve the article. We have documented the adjustments below.
This manuscript appears to have been previously revised; therefore, several questions have been answered in the current version.
However, I think there are some issues that need to be modified for possible publication of the manuscript.
Introduction: There are numerous errors in reference numbers
when they are continuous. For example, line 33: [1,2,3]. According to the instructions for the authors, they should be indicated as [1-3].
The same situation in line 38: [4,5,6,7,8,9], should be: [4-9]. Please refer to the instructions for authors https://www.mdpi.com/journal/applsci/instructions
and check the references throughout the manuscript.
We have reviewed the citation and made appropriate changes.
Material and methods: lines 150-151. Could they have affected the sequence set in the results obtained? Could not a randomized sequence have been better so that there were no effects of fatigue and / or learning / training of the participants?
Please indicate this in the discussion or study limitations.
we have added the following addition to the discussion.
For the measurements with test persons, fixed position marks for the test persons' feet were placed on the test objects and the test person was instructed in the correct body posture. Instructions were given to the test supervisor on how to set up and conduct the test. The standardized instruction for the test procedure with test persons included a short briefing on how to carry out the test as well as an explanation of the termination conditions (posture of the arms, changes in the foot position, putting one leg down in the monpedal position, etc.). A fixed sequence of the measuring program is preset by the software and is presented step by step on the screen to the person performing the test. Since each standing position is only completed once and all are completed in short succession, it can be assumed that there are no learning effects. To prevent fatigue, the test persons are required to perform short movement units between the individual measurements and the sequence is structured so that monopedal measurements alternate with bipedal measurements. The measures taken make it possible to conclude that differences that arise when several different persons perform the measurements were not to be expected.
Data Analysis: A more in-depth description of the statistical analyzes carried out is necessary, indicating the objective of each analysis. For example, describe the ANOVA. And so with all the analyzes carried out.
we have added the following addition:
To investigate differences between the measurement groups knee.flexion / knee.without.flexion is examined with a single factor ANOVA. To analyses the differences between the measurement groups man / woman and pain / no pain, is tested with a multifactorial ANOVA. To confirm possible effects, the power and eta² are calculated
Results: Line 191. “Overview” must start with a capital letter.
Change
Table 2. There are dots (.) between the words instead of bar space.
Change
Line 193. Table “two” is better at number 2.
Change
Line 203. “figure” must start in a capital letter: Figure
Change
Line 204: “table” must start in a capital letter: Table
Change
Table 4. Table 2. There are dots (.) between the words instead of bar space.
Change
References, Please check all references, there are some errors. For example, in several of them, No. appears According to the instructions, this should not be For example, in the references, 4, 6, 31, 32, 33, ...
Add a space between Gait & Posture in all the references of this magazine. For example, references #: 9, 19, 33, ...
The words of the title of the reference nº36 are in capital letters.
Reference nº 41, there is a double dot ".."
Reference numbers 44 and 46, the pages are missing.
References nº53, 54, and 55, the year is missing.
We have reviewed the citation and made appropriate changes.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The authors present data from models of human postural stability and from persons with and without back pain. The methods are not sufficiently described or justified, and the statistical analysis requires significant attention. As such, the discussion is not adequate, nor conclusions supported by the data.
General Comments
Spell check and review grammar throughout. Specific examples noted below.
The qualitative descriptions of the power spectral density are not adequate for addressing the research question. The noted observations of the authors are not inherently clear to the reviewer. Quantitative comparisons of the flexion of the knee (Figure 4) for example, would be helpful in characterizing the performance of these two conditions.
The statistical analysis is completely inadequate. The authors should refer to a statistician in performing the comparisons among groups and this will assist in interpreting resulting values. For example, a p value greater than the alpha level indicates there is not a significant difference (e.g., Page7 Line 185).
Given the lack of sufficient statistical analysis and interpretation the connection between the dynamic models and the human participant data is tenuous. What is the purpose of including each? The model reflected known perturbations that the authors expected to occur from the literature. Whereas the human participants were not considered from this perspective, but rather from a knee flexion and back pain perspective. Why? It seems like multiple, unconnected projects are connected with no particular justification.
Quantitative data to support the conclusions is necessary. The authors use expected values from the literature as perturbations in a simulated model and then conclude that these must be true of live persons, but without verification.
The discussion should summarize findings (which at present are lacking in general) and provide context for this by referencing the literature. At present, the discussion is more of a literature review similar to the introduction explaining underlying mechanisms and theories explaining postural stability.
Specific Comments
Abstract. Why is Postural capitalized in the first sentence? This also has an unnecessary space before the period.
Abstract. CoP-track? Or CoP-tracing? What is ‘tack’?
Page 3 Line 70. …movements are examined. Also, remove the extra close parenthesis after [33]
Page 4 Line 89. Remove ‘stand’ from this sentence
Page 4 Line 99. Is there a reference for Zatsiorsky?
Page 4 Line 102. Why is this reference spelled out in text not using the reference style of the journal?
Page 4 Line 114. The knee and ankle joint controls are…
Page 5 Figure 2. Why are the text descriptions not in English for this figure?
Page 5 Lines 128-133. Was the experiment approved by a local review board? Did the participants provide informed consent to participate? How were these persons recruited for the study? Why were these sample sizes selected?
Page 5 Lines 128-133. Why are descriptive statistics not provided for these individuals? Why are the sample sizes so drastically different? How do these groups compare on their demographic information besides the pain level?
Page 5 Lines 128-133.Were these tasks performed barefoot? Were the participants instructed to close their eyes or focus on a stationary target? Why was the foot placement standardized for all persons to an absolute location rather than relative to shoulder width or some other anthropometric factor? Where did the participants place their hands? Is the resulting 10 second trial length sufficient to address the question at hand? Is there a reference for using a single, short trial to evaluate these measures?
Page 5 Line 138. The period should be after al not the et in the reference (et al.).
Page 5 Line 139-140. …of the measurement series [were] removed after filtering.
Page 5 Line 142. Sensor raw data suggests you used the unfiltered CoP trajectories, but I imagine this is not the case. What metric do you mean by CoP track? Is this the length of the CoP path in a particular dimension or the resultant? Is there a reference for these processes?
Page 5 Line 151. How long was the model allowed to run? Why did the model get longer time to function (20 s at least) than the human participants that were collected for validation?
Page 6 Line 165. Do the authors mean Figure 4? Why are the spectral density measures only described qualitatively? Why not a quantitative analysis for the frequency spectra?
Page 6 Figure 4. Where is this one-legged stance coming from? In the methods it is implied that the participants performed two-legged stance, not single so where are these data coming from? If the participants actually performed the test on one limb, which did they choose or were they told to use a particular limb (e.g., dominance, right only)?
Page 7 Table 1. It is not clear what the authors are doing here. What is the F test doing and what is the t test doing? How are these groups being compared? Are you crossing back pain with gender somehow? A t test would not be appropriate for this. You have a 2x2 ANOVA it seems (men/women by pain/no pain).
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Title.
No abbreviations should be placed in the title (CoP).
Material and methods. Structure of the triple inverted pendulum.
It is necessary that the authors include the citations referring to Saziorsky and Gunter, to be able to review them and check how the weight distribution has been done, and the adaptation that the authors made in the design of the damping systems in the joints and muscles.
Studies on test persons.
The characterization of the sample is not well defined. The authors assume “for parameterization a human being with a size of 180 cm and a mass of 75 kg”. Therefore, it is necessary to check how closely the populations studied resemble the assumed population. The authors have to describe the anthropometric data (height, weight, mean, deviations and confidence intervals) of the two populations studied with and without pain in order to check how closely their data resembles the assumed model. They can be described in a table.
Data Analysis.
Authors should describe in more detail where the measurements were made. They should also point out the team's experience in evaluating people using the LabVIEW software tool.
References
Some of the references are poorly cited, they lack the year the article was published (5,14,15,18,32,51,52).
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors present data from models of human postural stability and from persons with and without back pain. The authors have updated their methods, but the statistical analysis is still insufficient. Interpretations of the statistical results are also erroneous. Despite updating some of the results the discussion is still in its original form. As such, the discussion is still not adequate, nor conclusions supported by the data.
General Comments
The qualitative descriptions of the power spectral density are not adequate for addressing the research question. The authors state in their responses that they could not provide descriptive statistics for the data. Why? If they are able to provide numerical scores to a statistical model (i.e., ANOVA) they can report averages and standard deviations at a minimum. Readers cannot evaluate the effects the authors report without this data.
The discussion should summarize findings (which at present are lacking in general) and provide context for this by referencing the literature. At present, the discussion is more of a literature review similar to the introduction explaining underlying mechanisms and theories explaining postural stability. This discussion was not even edited to reflect the updated Results section much less address this comment from the previous review.
Specific Comments
Abstract. It is unclear what data at the end show. The reader does not know if these are conclusions from the current study or ranges taken from the literature. Again, statistical information or descriptive statistics would help here.
Page 4 Line 99. Is there a reference for Zatsiorsky? That researcher’s name is still spelled incorrectly.
Page 5 Line 129. The second sentence does not start with a capital letter
Page 5 Line 132. Why is ‘Part’ capitalized in the middle of the sentence?
Page 7 Line 186. Which figure does this line refer to? It is labeled figure x.
Page 8 Lines 205-208. ANOVA does not show correlations. Again, no actual data are presented which is an issue as well. This reviewer again recommends that the authors consult a statistician to help perform their statistical analyses. A p value of .05 is not a significant result nor does it represent a ‘weak’ result. If the authors want to contextualize the magnitude of differences they should include effect sizes.
Reviewer 2 Report
The authors should review some minor errors that exist, such as font, italics, etc., to adapt to the format of the journal.
