Development of a Simplified Human Body Model for Movement Simulations

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper aimed to develop a simplified human model modified from the Hanavan model based on anthropometric data. The authors claimed reproducing human movements with the developed model is possible by testing it on one volunteer performing three motion tasks. The paper has a good structure. My major concerns are: (1) simulation was only conducted on one data point (height 187 cm and mass 70 kg); (2) data collection was only performed on one volunteer with inertial sensors instead of optical motion capture systems; (3) there are no reference points to help understand whether the simplified human model is accurate or not; and (4) the comparison between the new simplified model and previous models is not enough. I would recommend the authors address the comments from reviewers and resubmit the paper after that. 

Please find detailed comments for each section of the study:

1. Abstract: The evaluation part of the human model is not clear. How the model is tested and the testing results are not clearly shown in the abstract.

2. Introduction: Paragraphs 1 and 2 did not give a good summary of the application of IMU and commonly used measurements from equipment.

3. Introduction: Paragraphs 4-7 do not fit well as an introduction. A short introduction of each model and a description of each model to recent academic research and findings are recommended instead of a list of well-described models.

4. Introduction: The research gap is not clear. Why a simplified human body model is needed. Why the Hanavan model was chosen.

5. Methods 2.1: It is not clear to me by checking Figure 2, how the human body model was simplified.  Section 2.1 needs to be re-organized and reformatted to reduce unnecessary details and highlight important changes.

6. Methods 2.2: the model was simulated purely on one dimension (height 187 cm and mass 70 kg). I am not sure whether it is generalizable enough or not.

7. Methods 2.3: the data was collected only on one volunteer. I am not sure whether it is generalizable enough or not.

8. Methods 2.3 & 2.4: Since the objective is to build a human body model, why not use an optical motion capture system instead of IMUs? IMU has drifting issues, and the data accuracy is not comparable to an optical motion capture system like Vicon. Given that human data was collected in a open and clear space, a optical motion capture system is recommended.

9. Results: The results covered considerable aspects of the model. But a reference/golden standard is missing. It is hard to make a judgment on whether the model is good or not.

10. Results: It is also recommended to put some effort into trunk/torso results demonstration.

11. Results and Discussions: The key contribution of the study is to simplify the human model, however, it is hard to understand from the result section what aspects the new human model outperforms previous models and what are the tradeoffs.

12. Discussion: Not many related studies are mentioned in the discussion part.

13. A conclusion section is missing.

Comments on the Quality of English Language

Need to proofread and rewrite some of the parts to make the manuscript easier to understand. 

Author Response

We would like to thank the reviewer for valuable remarks.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors discuss the development of a simplified human body model for movement simulations. The proposed model is validated through an experimental measurement campaign based on a distributed IMU system. The paper is interesting, but it lacks some details before I can recommend it for publication. My comments are below, but first, the authors must perform a careful English language revision because some parts of the paper are difficult to read due to serious language flaws.

l. 77-79: Be sure to have the rights to reproduce or to include in your paper those figures.

l.83-92: As far as reading through the introduction, the contribution of this paper is rather obscure. I suggest including in the last part of the introduction a clear statement of the main contribution(s) of the manuscript, along with a description of the paper's organization throughout the various sections.

l.95-97: Please revise the phrases' language construction which sometimes is rather misunderstandable

l.102: What is model 17? Maybe a comma is missing?

l.185: The authors should put here a reference to the datasheet of the employed IMU sensors system. Moreover, they should describe in detail the characteristics of the sensors, the reasons why they placed the sensors in specific body parts, and the reasons behind these choices. Moreover, I suggest they reference a research work that discusses a hot topic that should be considered when considering multiple IMU sensors placed along a body, i.e. the temporal synchronization of the data gathered from such sensor systems. In this specific scenario, many artifacts may arise due to a lack of synchronization especially in gait analysis. Several works discuss this problem in literature, e.g. studies on IMU sampling rate mismatch for a wireless synchronized measurement platform

 

- The conclusions are missing, therefore the contribution of the paper is not still clearly highlighted.

Comments on the Quality of English Language

The authors must perform a careful English language revision because some parts of the paper are difficult to read due to serious language flaws.

Author Response

We would like to thank the reviewer for valuable remarks.

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

 

The authors have addressed most of the concerns effectively; however, one major issue remains unresolved. The manuscript does not sufficiently test or document the performance of the simplified model. Specifically: 

1. Standards for human motion are either unclear or not adequately described in the Methods and Results sections. 

2. The data was collected from only a single volunteer, which significantly limits the reliability of the findings.

3. The comparison of the new model with other models focuses only on features rather than the model performance/accuracy, leaving a critical gap in the evaluation.

Additionally, the model lacks generalizability for broader applications. More experimentation involving diverse body dimensions is necessary to validate its applicability across a wider range of population groups.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors addressed almost of my previous concerns, making a huge improvement in the paper quality from the first review rounds. However, there are still some minor revisions which must be implemented before I can recommend the paper for publication.

-Figure 3: I think this Figure may have the same problem as the old Figure 1. Therefore, I kindly ask the authors to check to have the rights of reproduce every figure they take form other sources than being built by themselves.

 

- The conclusions are now maybe too verbose and redundant with respect to the rest of the paper, i.e. the results section must discuss the results, while the conclusions should wrap-up the paper contents from the initial claim to the proved findings in few lines.

Comments on the Quality of English Language

The quality of English has been improved.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have resolved most of my concerns. Congratulations on the great work.