A New Approach to Prevent Injuries Related to Manual Handling of Carts: Correcting Resistive Forces between Floors and Wheels to Evaluate the Maximal Load Capacity

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General Comments

This is an interesting study, assessing resistive force for different wheels of varying characteristics moving on one steel plate and on four resilient floor coverings. To characterise the resistive force of different types of wheels and floors, an original  test bench was developed. Forty-four different wheels were tested, whereas a wheel was characterised by its diameter, tread and wheel bearing. The results of this study indicated that the resistive force increased linearly with the load, whereas its depended on both the wheel’s characteristics (diameter, type of tread and type of bearing) and the type of floor. The resistive force decreased with the wheel diameter, however, when the wheel diameter had exceeded 100 mm, the influence of diameter was less significant.  Although the resistive force depended of the type of tread, it did not depend on the hardness of the tread, whereas it was higher for wheels with solid rubber tread.

The manuscript is generally well written. However, the design of this paper should be improved before publishing. In my opinion, it is obligatory:

(1)  To to present significance of differences  (p<0.05) between different floors and wheels when resistive force was measured in Abstract. (Which types of floors and wheels differed significantly during measurement of resistive force?). In the present form, the results of this study are presented without statistical support (too general) in the Abstract.

 

(2) To to present statistical significance on figures in Results (Fig.2-6) for better illustration of the significant differences  (* p<0.05) between different floors and wheels when resistive force was measured.

Specific Comments

Abstract

Please present significance of differences  (p<0.05) between different floors and wheels when resistive force was measured in Abstract (see General Comments).

3. Results

Please present statistical significance (* p<0.05) on figures (see General Comments)  as follows:

Figure 2 – between different floors

Figure 3 – between different wheel types

Figure 4 – between different wheel diameter

Figure 5 – between different wheels` bearings

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This is a study measuring the effects of different load, floor covering, wheel’s tread, bearing and diameter on wheel’s resistive force, because, according to authors, such force is believed to be linked to increased risk of developing musculoskeletal (msk) conditions. The experiments appear to have been well conducted and the reporting, in general, is sufficiently detailed to allow replication. Yet, each manuscript section has important shortcomings that prevents me to accept the article for publication in its current version. In the Introduction, what types of MSK conditions, including the body region, are commonly developed when using manually propelled wheeled equipment and under what circumstances (e.g., somewhat continuous versus intermittent use; years of work, etc.) are not reviewed by the authors, leaving readers with incomplete information on this topic and questioning about the relevance of the study. My argument is reinforced by the complete absence of how the findings from this study can contribute to prevent such msk conditions in the Discussion section. There are some highly vague allusions to that, in lines 339 and 376, abruptly diminishing the interest of this article to many readers. This is like saying nutrition is good for your health. We already know that, as we already know that forces acting on the human body can injure it if (simply speaking), e.g., the limits of the elastic phase of a stress-strain curve of a msk tissue are exceed. How “correcting resistive forces between floors and wheels to evaluate the maximal load capacity” may “prevent injuries related to manual handling of carts” based on your findings (and others) is the rationale that needs to be discussed, otherwise your Title is overly speculative.

 

SPECIFIC SUGGESTIONS

 

Line 30: This sentence makes poor sense. Do you mean “disability” instead of “injuries”? Also, there are more robust references, even from WHO, to stress this fact.

 

Line 44: I suggest also mentioning “rolling friction” as a frequently used synonym of “rolling resistance”.

 

I think it is missing in the Introduction what are the most common msk injuries that may occur when operating a manual cart and how the biomechanics of such operating interacts with other factors (age, sex, overall workload, etc.), so that readers can appraise how important is this study. You have some interesting explanations/arguments, but they are incomplete.

 

Line 104: Tell us what software was used for computation of the signal average. Matlab?

 

Lines 167–184: I think you need to inform readers more about that linear mixed model works. It seems a little bit like ANCOVA (combining analysis of variance with linear regression) but further explanations are necessary so that readers can better interpret your results. For example, R square is already a measure of effect size. Why choosing Cohen’s d? Are you comparing the size of the differences between two means? I later discovered (results) you were, but I was not sufficiently informed previously on why and how. Many potential readers may not be familiarized on those statistical procedures. You need to sufficiently explain them so that can understand your results.

 

Lines 190, 232 and others: p=0.0000 looks weird. You may report p<.001

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The study is interesting and generally well written and documented with the research and results obtained.

The introduction requires more detail. I propose to specify the nature of the trolleys (scope of work performed, load on the trolleys) with the characteristics included in the research.

The final conclusions are very laconic. I recommend that they be more closely related to the obtained research results. How does this reschedule into practical use of the type of wheels.

The literature was selected correctly.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The design of this manuscript was improved in the process of review.

Reviewer 2 Report

Comments and Suggestions for Authors

I'm satisfied with the explanations provided by the authors and the amendments they've performed. They refer to Annex A and B in the text, lines 70 and 74, respectively, however, this is not presented.

Reviewer 3 Report

Comments and Suggestions for Authors

After making corrections, the work may be accepted for publication.