Running Experimental Research of a Cable-Driven Astronaut on-Orbit Physical Exercise Equipment

Round 1

Reviewer 1 Report

The paper with title "Running Experimental Research of a Cable-Driven Astronaut on-orbit Physical Exercise Equipment" provides a significant insight and contribution to the field, but some minimal corrections and improvements must be done to the paper in order to consider the paper for publication:

 

1. What occurs in line 276 of page 14? Please specify and explain why the root mean square error of Fz (6.5770 N) is smaller. This means, is someone is not familiarized with this measurements please add a comparative table for example, in which it can be determined how small is the RMSE.

2.  Which kind of disturbance exists in the design of this equipment? this means the physical interpretation of the disturbances that it could be possibly generated by the tension of the astronaut's body? Please explain well this.

3. Explain well in a paragraph the optimization method which appears in equations (10) and (11). Explain how E(t) was selected? and the relation that exist between the selection of \lambda and the optimal solution for the objective function F(\lambda)

 

4. Explain please in page 3 the selection of \lambda. How this parameter is selected?

 

a) Is there any systematical method to adjust this parameter considering that in equation (9) the limits of lambda are established but not a selection method.

5. It is "follow" instead of "fellow" in line 60 page 2.

 

Author Response

Dear reviewer,

Thanks for pointing out our shortage and mistakes. 

We have revised our manuscript according to your advice and the reply letter is attached.

Thanks again for your time and comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

The subject of the paper is of great interest in developing original cable-driven exercisers (in general and for assisting astronauts, especially). The paper represents a good work and yours experience and results might stimulate discussion regarding this topic. Please consider following suggestions:

- please correct or complete the incomplete sentence in the Abstract: “In order to mitigate or eliminate the negative influence of the microgravity.”

 - although the list of references is adequate, I would recommend updating it with References from recent years, given that the newest are from 2019;

- although the Introduction presents some examples of exercisers for the same kind of applications (for astronauts) , no details are given regarding their structure and design; I think it would be useful to analyze other cable-driven exercisers, even if they are used in traditional rehabilitation approaches;

- please argue some of the specified advantages: user-friendly, easy maintenance, etc.

- please emphasize elements of novelty and originality of this paper, specify the original contributions of this paper, in relation to other equipment developed to assist astronauts in different physical exercises;

- please extend some of yours conclusions and add comments / give more details regarding your  future work in this area.

Author Response

Dear reviewer,

Thank you so much for your comments, and they are important for us to improve our manuscript. 

We have revised our manuscript according to your advice and the reply letter is attached.

Thanks again for your time and comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors of this work present a novel piece of equipment called CAPE, which is supposed to be an evolution in terms of technology of the state of the art tools used to prevent astronauts health problems, due to poor physical exercise. The paper is well written and easy to follow. However, I’m not fully convinced that the presented results prove the claims of the authors: above all, I’m not convinced it’s a user-friendly and small device. The experiment is nothing but just a very preliminary proof-of-concept in a simulated environment. Despite the authors suggest the use of CAPE as a multi-modal machine, only the safety protection strategy is really showed and tested. The reviewer suggests to fully provide evidence of the authors’ claims over the current state of the art. Finally, it’s not clear what the experiment and the simulation goals are: there is no objective (or it is unclear) before the plots.

 

Major comments:

• I’m not convinced by the simulation and experiment that the CAPE was tested for all proposed scenarios. Indeed, it seems it’s been tested only as a safety protection to astronauts when running on the treadmill. It should be instead showed how the same structure can be used to accomplish bench press, squat, deadlift, etc.
• The CAPE is presented as user friendly but it does not look like something much simpler to use/wear than a standard exoskeleton, and small in space occupation, but it does look like cables and pulleys need a certain non-negligible distance from the user.

Minor comments:

• Line 3-4: the sentence “in order to mitigate…” ends too early.
• The experiment is rather just a proof-of-concept, given that it is a very tiny testing population and just one condition.

Author Response

Dear reviewer,

Thanks for pointing out our shortage and mistakes. 

We have revised our manuscript according to your advice and the reply letter is attached.

Thanks again for your time and comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

I thank the authors and believe all my concerns were addressed. Probably a change in the title (introducing somewhere the word "preliminary") would help better shaping the focus of the work.