Gender-Based Differences in Actual Thumb Force Exertions at Various Target Force Levels

Round 1

Reviewer 1 Report

The author's report on their study regarding the relationship between perceived and real thumb force exertion. The study is well designed, however the discussion in particular requires improvement. My feedback follows.

Line 54-55 the full names of the tools should be stated then abbreviated in brackets.

Line 74-77 mention that Borg's CR10 scale is 'one of the representative methods of self-report...' however the authors have not stated why this scale was not used in their study.

2.1 The sample size should be justified.

Throughout the tables/figures need to be able to be interpreted by themselves, therefore abbreviations need to be reported in full as a footnote.

Line 90 - please explain why you have hypothesised a non-linear relationship, and what relationship you expected.

The discussion should start with a restatement of the research question, and the key results.

Line 210-222 isn't directly relevant to the study, as the study focused on the relationship between real and perceived force. I would recommend removing or condensing (and putting later) the discussion regarding the gender differences in the force exerted.

There should be a discussion regarding the findings of this study with regards to Borg's (and others) findings regarding the relationship between perceptions/ real exertion. In particular, why do the authors think there was an S-shaped curve?

The discussion should include a discussion regarding the implications of this finding. Can self-report measures be used? How might these perceptions change with 'real' work tasks? What future research do you recommend?

The 50% phenomenon has not been described. Could the authors please state what they mean.

Don't start sentences with abbreviations (e.g. line 255).

The conclusion shouldn't state differences in the MTF by gender as this does not answer the research question. The conclusion should focus simply on the findings that answer their question and the implications of these findings.

There are several grammatical issues that need to be addressed. I would suggest careful editing of this manuscript.

Author Response

Reviewer 1’s comments

1) Line 54-55 the full names of the tools should be stated then abbreviated in brackets.

- It has been deleted because another reviewer has proposed to delete the contents of this section.

 

2) Line 74-77 mention that Borg's CR10 scale is 'one of the representative methods of self-report...' however the authors have not stated why this scale was not used in their study.

- Thank you for your valuable comment. A relevant description has been added to the introduction.

[Although many researchers reported that the Borg’s CR-10 scale is one of representative methods of self-report estimating subjective exertion, there are still many studies reported that perceived exertions may vary depending on the type of muscle. Frank et al.[16] conducted an experiment to study the relationship between subjective perceived exertion and action force exertions in maintaining the same force levels (20% MVC) on the legs and arms for five minutes exercise time. The results showed significant differences in perceived exertion levels depending on the type of muscle (the RPE in the legs was greater than the force of the arm). As we know, Borg's CR-10 scale was developed based on %MVC, and multiplied by 10 on the Borg CR-10 scale will result in %MVC (i.e., 5 on the Borg CR-10 scale corresponds to 50%MVC).

Thus, %MVC was used instead of Borg CR-10 scales as a measure of subjective perceived exertions in this study to understand the relationship between perceived and actual thumb force exertion levels.]

 

3) 2.1 The sample size should be justified.

- Total number of participants was described in section 2.1 and a total number of exertions for maximum thumb force and %MVCs were also mentioned in section 2.3. In addition, the limitation of the imbalanced number of participants between males and females has also been added in discussion section.

[A total of 31 participants (23 males and 8 females) were recruited through advertising at Sungkyunkwan University.]

[Three repetitions for the maximum thumb force exertion were performed with a 3-min resting time between trials. The experimenter calculated the average of all the three maximum thumb forces of each participant and set an individual MTF for each participant. The experimenter randomly selected a perceived exertions level (% MTF), which was one of the five levels of % MTF (10%-90% MTF at an interval of 20%) with two repetitions. Thus, all participants were asked to exert 10 thumb force exertions for the perceived exertions level (% MTF), which was selected by experimenter based on their own judgment for 5 s (Figure 2).]

[Therefore, in further studies, consideration should be given to the various participants (age, gender, industry, anthropometric characteristics, etc.) to complement the limitations of this study.]

 

4) Throughout the tables/figures need to be able to be interpreted by themselves, therefore abbreviations need to be reported in full as a footnote.

- All abbreviations have been revised as a reviewer’s comment.

 

5) Line 90 - please explain why you have hypothesised a non-linear relationship, and what relationship you expected.

- Many previous researches reported that there is a non-linear relationship between perceived exertions and actual exerted forces. Based on the previous studies, we also expected the non-linear relationship in the thumb force exertions. Following sentences have been added in introduction section.

[In previous studies that evaluated perceived ratings for grip strength, the results also indicated a nonlinear relationship between perceived and actual force exertions [11]. Pinchvero et al [17, 18] also reported that the relationship between perceived and actual force exertion had a nonlinear form.]

 

6) The discussion should start with a restatement of the research question, and the key results.

- As reviewer’s recommendation, it has been revised in discussion section.

[This study was conducted to investigate the relationship between actual thumb force exertion and perceived thumb force exertion using the Borg’s CR-10 scale. It has been shown that the relationship between actual and perceived thumb force exertions was a non-linear S-shape curve. Most participants exerted their actual thumb force accurately at 50% MTF with high accuracy. Based on the 50% MTF level, an over-exertion was observed at 50% MTF or below, and under-exertion was founded at 50% MTF level or above, thus named the ‘50% phenomenon’.]

 

7) Line 210-222 isn't directly relevant to the study, as the study focused on the relationship between real and perceived force. I would recommend removing or condensing (and putting later) the discussion regarding the gender differences in the force exerted.

- Authors agreed with some parts of your opinion. Thus, authors removed and revised some sentences which were irrelevant part based on reviewer’s comment.

[Many previous studies reported that the maximum forces exerted by males were greater than those of females in pinching, grasping, and lifting tasks [21],[22]. In studies of elbow flexion and grip strength, females exerted 39.5-45.0% [23],[24] and 52.9-62.3% [25]-[28] of male strength, respectively. According to the thumb force exertion studies [29]-[31], females also exerted lower thumb forces (64.1-97.1%) than males. The current study finding was similar to that of previous studies involving thumb force exertions (female MTF was about 73.6% that of males).

The difference between males and females in terms of maximum muscle exertions might be attributed to the size of physiological cross-sectional areas (PCSA) of muscle groups [32],[33].]

 

8) There should be a discussion regarding the findings of this study with regards to Borg's (and others) findings regarding the relationship between perceptions/ real exertion. In particular, why do the authors think there was an S-shaped curve?

- The following sentences have been added in discussion section.

[Thus, the relationship between perceived thumb force exertion level (% MTF) and actual force exerted thumb force (% MTF) showed an S-shaped pattern (Figure 4). It means that a tendency for people to exert higher and lower thumb forces than perceived exertion force levels at lower and higher than 50% MTF levels, respectively, as shown in Figure 4. That is, the point of 50% MTF is kind of inflection point where curves change from concave to convex. It suggests that the participants were biased to over-exertion under the 50% MTF level, and under-exertion above the 50% MTF level, respectively.]

 

9) The discussion should include a discussion regarding the implications of this finding. Can self-report measures be used? How might these perceptions change with 'real' work tasks? What future research do you recommend?

- As your recommendation, the implication and future research have been added in discussion.

[The findings of this study may be useful in assessing the workload of workers who are using thumb exertion forces in the manufacturing process. As noted earlier in the introduction section, direct measurement of load cells has the advantage of accuracy, but is not suitable for the actual work sites due to costly and time-consuming issues. Through the regression equation derived from our research, the workers’ thumb exertions could be measured easily and accurately (both regression model with an R² of more than 0.99). In addition, our research findings could have a positive effect on the prevention of WMSDs at work sites. Accurate measurement of risk factors is essential for the introduction of interventions to improve the manufacturing line. Therefore, it is necessary to find an easy and simple way to effectively assess the risk factors for thumb-related WMSDs.]

[Therefore, in further studies, consideration should be given to the various participants (age, gender, industry, anthropometric characteristics, etc.) to complement the limitations of this study.

Other limits were not considered variables that would affect our results, such as weight, height, and hand grip strength. In order to overcome these limitations, more variable studies should be considered.]

 

10) The 50% phenomenon has not been described. Could the authors please state what they mean.

- The following sentences have been added in discussion section.

[This study was conducted to investigate the relationship between actual thumb force exertion and perceived thumb force exertion using the Borg’s CR-10 scale. It has been shown that the relationship between actual and perceived thumb force exertions was a non-linear S-shape curve. Most participants exerted their actual thumb force accurately at 50% MTF with high accuracy. Based on the 50% MTF level, an over-exertion was observed at 50% MTF or below, and under-exertion was founded at 50% MTF level or above, thus named the ‘50% phenomenon’.]

[Thus, the relationship between perceived thumb force exertion level (% MTF) and actual force exerted thumb force (% MTF) showed an S-shaped pattern (Figure 4). It means that a tendency for people to exert higher and lower thumb forces than perceived exertion force levels at lower and higher than 50% MTF levels, respectively, as shown in Figure 4. That is, the point of 50% MTF is kind of inflection point where curves change from concave to convex. It suggests that the participants were biased to over-exertion under the 50% MTF level, and under-exertion above the 50% MTF level, respectively.]

 

11) Don't start sentences with abbreviations (e.g. line 255).

- It have been revised. [Maximum Thumb Forces (MTF) ~]

 

12) The conclusion shouldn't state differences in the MTF by gender as this does not answer the research question. The conclusion should focus simply on the findings that answer their question and the implications of these findings.

- Although gender effect of MTF was not main purpose of this study, authors thought that this finding was also would be valuable data. As your comment, the following sentence has been added in conclusion.

[The results of this study can provide an easy and accurate method of estimating the thumb force in the manufacturing field. Data from this study can also be used as a guideline for thumb pressing work which often occur in the industries such as automobile assembling lines.]

 

13) There are several grammatical issues that need to be addressed. I would suggest careful editing of this manuscript.

- Thanks for your suggestion. Overall the manuscript has been carefully revised.

 

I would like to say thank you again for your valuable comments.

Reviewer 2 Report

I see three important contributions of this work:

1) the data about male and female thumb strength. There are only a few studies of thumb strength, e.b., Kroemer. Thumb strength is an important consideration in the design of many tools and work tasks.

2) the accuracy with which subjects can exert a required force.

3) the tendency of subjects to exert an excess force (what Westling and Johansson (1984) refer to as "safety Margin")

All of these findings have been previously reported, but really only the first item for the thumb.

Weaknesses of this study include:

1) The background regarding thumb injuries is confused and fails to provide a solid rationale for this study. A thumb injury could be anything from amputation to a blister.  Thumb strength is an important consideration in tool design and important in its own right. The discussion about hand injuries only confuses the issue and doesn't have anything to do with the final conclusions.

2) the Slocum and Swanson references are not obsolete, but there is a whole body of literature that this much more up to date. I've listed a few examples below.

3) It is not clear how representative the subjects are of the working population, which seems to be the target of this work. (lines 255-261)

4) It is not clear why the study is imbalanced between males and females. It is not clear if only gender was included in the analysis or if other factors such as subject weight, height and hand size were also included, but were found not to be significant. Generally, these other factors will because they also are related to gender.

5) There is quite a lot of relevant literature on psychophysics as it relates to the force of exertion. (See selected references below)

6) corresponding data on grip force should be included if it is available. It would be very useful to know how these thumb strengths correspond to hand strength.

7) You report that exertion force is only affected by gender, but presumably, hand strength also would be an important factor if, for no other reason, hand force and gender are related. 

In summary, this paper provides some new data regarding thumb strength and exertion force. The background and conclusions are not well well developed. The literature review is incomplete. The selection of subjects and anthropometrics may be problems.

 

 

 

Bao, Stephen, Peregrin Spielholz, Ninica Howard, and Barbara Silverstein. "Force measurement in field ergonomics research and application." International Journal of Industrial Ergonomics 39, no. 2 (2009): 333-340.   Lowe, Brian D. "Effect of carpal tunnel syndrome on grip force coordination on hand tools." Ergonomics 42, no. 4 (1999): 550-564.
  Dale, Ann Marie, Amanda E. Rohn, Amanda Patton, John Standeven, and Bradley Evanoff. "Variability and misclassification of worker estimated hand force." Applied ergonomics 42, no. 6 (2011): 846-851.
  Raghu Prasad, M. S., and M. Manivannan. "Comparison of force matching performance in conventional and laparoscopic force-based task." In Proceedings of the Human Factors and Ergonomics Society Annual Meeting, vol. 58, no. 1, pp. 683-687. Sage CA: Los Angeles, CA: SAGE Publications, 2014.

Chung, Kevin C., Jennifer B. Hamill, Madonna R. Walters, and Rodney A. Hayward. "The Michigan Hand Outcomes Questionnaire (MHQ): assessment of responsiveness to clinical change." Annals of plastic surgery 42, no. 6 (1999): 619-622.

Figueroa-Jacinto, R., T. J. Armstrong, and W. Zhou. "Normal force distribution and posture of a hand pressing on a flat surface." Journal of biomechanics 79 (2018): 164-172.

Kroemer, K. H., and E. M. Gienapp. "Hand-held device to measure finger (thumb) strength." Journal of applied physiology 29, no. 4 (1970): 526-527.

Dong, H., Barr, A., Loomer, P., & Rempel, D. (2005). The effects of finger rest positions on hand muscle load and pinch force in simulated dental hygiene work. Journal of Dental Education, 69(4), 453-460.

Marshall, Matthew M., Thomas J. Armstrong, and Marissa L. Ebersole. "Verbal estimation of peak exertion intensity." Human factors 46, no. 4 (2004): 697-710.

Seo, Na Jin, and Thomas J. Armstrong. "Investigation of grip force, normal force, contact area, hand size, and handle size for cylindrical handles." Human Factors 50, no. 5 (2008): 734-744.

Stevens, S.S., 1957. On the psychophysical law. Psychological review, 64(3), p.153.

Swanson, A.; Göran-Hagert, C.; de Groot Swanson, G. Evaluation of impairment in the upper extremity. J. Hand. Surg. Am. 1987, 12, pp. 896–926.

Westling, G., & Johansson, R. S. (1984). Factors influencing the force control during precision grip. Experimental Brain Research, 53, 277–284. 

Author Response

Reviewer 2’s comments

1) The background regarding thumb injuries is confused and fails to provide a solid rationale for this study. A thumb injury could be anything from amputation to a blister. Thumb strength is an important consideration in tool design and important in its own right. The discussion about hand injuries only confuses the issue and doesn't have anything to do with the final conclusions.

- Thanks for your comments. The authors agree with you. In the industrial sector, excessive thumb force could be a major cause of occupational injury and WMSDs. The authors thought that the accurate measurement of the thumb force exerted during the work should preced. If proper intervention is introduced in the workplace according to the thumb force level, the prevalence rate of occupational injury and thumb-related WMSDs could be reduced. As reviewer’s recommendation, related contents have been added in introduction section.

[Manual tasks such as initiation of fastener and insertion of objects are frequently observed in the automotive assembly industry, and such tasks should exert excessive thumb force from 5.1 kgf to 17.0 kgf [5]. This could be an occupational injury and a risk factor that can contribute to the WMSD. Thus, the accurate measurement of the exertion level of the thumb at work and the application of appropriate intervention, such as personal protective equipment, or modification of facilities according to the thumb exertion level, are critical to preventing occupational injury and WMSD. However, few studies have been done on estimating the thumb exertions of workers carried out in the industrial sector.]

 

2) the Slocum and Swanson references are not obsolete, but there is a whole body of literature that this much more up to date. I've listed a few examples below.

- First of all, thank you for list-up the valuable references. It was a great help to improve our manuscript. As your recommendation, reference of Slocum and Swanson has been deleted and recent literatures have been added overall.

 

3) It is not clear how representative the subjects are of the working population, which seems to be the target of this work. (lines 255-261)

- The author agrees with the reviewer's comments. Participants recruited for this study may not represent the working population in terms of age and work expertise. For further research, we plan to conduct similar research for people in 40s and 50s. Thank you for your valuable opinion. A relevant explanation was added to the discussion section as a limitation of this study.

[There are several limitations to this study. As the first limit, our study only targeted participants in their 20s and may not represent the working population in manufacturing industry. Therefore, in further studies, consideration should be given to the various participants (age, gender, industry, anthropometric characteristics, etc.) to complement the limitations of this study.]

 

4) It is not clear why the study is imbalanced between males and females. It is not clear if only gender was included in the analysis or if other factors such as subject weight, height and hand size were also included, but were found not to be significant. Generally, these other factors will because they also are related to gender.

- The author agrees with the reviewer’s opinion. Characteristic of subjects such as gender, weight and hand size could influence the result of this study. Therefore, the description about limitation has been added in discussion section and author will try to compensate the limitations as reviewer’s comment in further study.

[There are several limitations to this study. As the first limit, our study only targeted participants in their 20s and may not represent the working population in manufacturing industry. Therefore, in further studies, consideration should be given to the various participants (age, gender, industry, anthropometric characteristics, etc.) to complement the limitations of this study. Other limits were not considered variables that would affect our results, such as weight, height, and hand grip strength. In order to overcome these limitations, more variable studies should be considered.]

 

5) There is quite a lot of relevant literature on psychophysics as it relates to the force of exertion. (See selected references below)

- Overall introduction section has been revised based on your recommendation.

 

6-7) corresponding data on grip force should be included if it is available. It would be very useful to know how these thumb strengths correspond to hand strength. You report that exertion force is only affected by gender, but presumably, hand strength also would be an important factor if, for no other reason, hand force and gender are related. 

- In this study, grip force wasn’t considered. However, authors agree with reviewer’s opinion that grip force might influence on the thumb force. As your recommendation, author will consider grip force in further study. The explanation about this limitation were added in discussion.

 [Other limits were not considered variables that would affect our results, such as weight, height, and hand grip strength. In order to overcome these limitations, more variable studies should be considered.]

 

 

In summary, this paper provides some new data regarding thumb strength and exertion force. The background and conclusions are not well developed. The literature review is incomplete. The selection of subjects and anthropometrics may be problems.

- The background and conclusions have been revised overall as your recommendation. The limitations regarding subject and anthropometric data also were added in discussion section.

 

I would like to say thank you again for your valuable comments.

Reviewer 3 Report

Dear Editor, 

This study measured the actual thumb force exertion and perceived thumb force exertion in the various levels of exertions from 10% to 90%. The authors wanted to investigate the relationship between different exertion levels and genders.

I found several limitations in his study. First of all, the introduction is full of unrelated facts, while the authors did not state precisely why they are interested in measuring force. The introduction must provide more information about the different types of forces (internal, external, mechanical, etc.), and those are focused on this study. The objective is to measure perceived thumb force exertion, but I saw neither in the method section nor in results measuring perceived force exertion.  The authors talk about the target and actual force while it is not clear what they mean by these notions?

Secondly, I think this study does not have any novelty as the main results and discussion are about the difference in the force between males and females, while these differences are evident. 

Furthermore, the authors did not explain very well their methodology. They should provide more details about the experimentation. Please see my comments in pdf.

In results, I could not understand that the statistical analysis was done between which variables. The tables and figures are complicated to follow. The author talks about the regression model while they did not explain in the method section this model and its variables. 

I put the comments in pdf for the authors.  

I think this article in the way that is presented is not acceptable for publishing in the journal. 

Comments for author File: Comments.pdf

Author Response

Reviewer 3’s comments

1) First of all, the introduction is full of unrelated facts, while the authors did not state precisely why they are interested in measuring force. The introduction must provide more information about the different types of forces (internal, external, mechanical, etc.), and those are focused on this study. The objective is to measure perceived thumb force exertion, but I saw neither in the method section nor in results measuring perceived force exertion.  The authors talk about the target and actual force while it is not clear what they mean by these notions?

- First of all, thank you for your valuable comments. As your recommendation, the unrelated materials have been removed. Background and rationale of this study have been enhanced in introduction section.

- In this study, target force has same meaning with the perceived exertion level. As your comment, ‘target force level’ have been replaced with the ‘perceived exertion’ overall.

 

[Manual tasks such as initiation of fastener and insertion of objects are frequently observed in the automotive assembly industry, and such tasks should exert excessive thumb force from 5.1 kgf to 17.0 kgf [5]. This could be an occupational injury and a risk factor that can contribute to the WMSD. Thus, the accurate measurement of the exertion level of the thumb at work and the application of appropriate intervention, such as personal protective equipment, or modification of facilities according to the thumb exertion level, are critical to preventing occupational injury and WMSD. However, few studies have been done on estimating the thumb exertions of workers carried out in the industrial sector.]

 

[Kong et al [11] and Prasad and Manivannan [12] reported that perception of hand grip force was different according to the handedness. As such, while much research has already been conducted on grip strength, very few studies has been done on thumb force exertions and self-reporting estimates, even though the thumb plays a major role in various hand functions [13]-[15].]

 

[Although many researchers reported that the Borg’s CR-10 scale is one of representative methods of self-report estimating subjective exertion, there are still many studies reported that perceived exertions may vary depending on the type of muscle. Frank et al.[16] conducted an experiment to study the relationship between subjective perceived exertion and action force exertions in maintaining the same force levels (20% MVC) on the legs and arms for five minutes exercise time. The results showed significant differences in perceived exertion levels depending on the type of muscle (the RPE in the legs was greater than the force of the arm). As we know, Borg's CR-10 scale was developed based on %MVC, and multiplied by 10 on the Borg CR-10 scale will result in %MVC (i.e., 5 on the Borg CR-10 scale corresponds to 50%MVC).]

 

2) Secondly, I think this study does not have any novelty as the main results and discussion are about the difference in the force between males and females, while these differences are evident. 

- It would be obvious that there is a difference in gender as your opinion, however, authors believed that the quantification of gender difference with specific figures could be important and meaningful data in a human engineering field. In addition, according to the results of relevant literature studies, there is very few study of thumb strength itself and/or the study of gender differences over thumb strength.

Therefore, it is believed that our findings can provide insights to researchers in the relevant research fields.

- Although the gender effect between perceived force and actual exerted force was not statistically significant, males tended to exert more accurate thumb forces than females. The author thought this was also a meaningful result.

 

3) Furthermore, the authors did not explain very well their methodology. They should provide more details about the experimentation.

- As your comments, more detail descriptions have been added as below.

 

(1) Picture of Sub-miniature load cell has been newly added in [2. Method, 2.2. Apparatus, Figure 1].

(2) Description about measurement program (software) has been added in method section.

[This software programmed to convert the output data of load cell (mV/V) into force value (N) and to measure the data in real-time. For the visual information, thumb force data is represented by a blue line on the screen in real-time (Figure 2, right)]

(3) Description about output data of loadcell also has been added in method section.

[Method, 2.2. Apparatus, Line 125] output (millivolts per volt; mV/V)

(4) Picture of participants already represented in method section [Method, 2.2 Apparatus, Figure 2, left]

 

(5) The references of maximum task time (5 s) has been also added [Method, 2.3.Experimental procedure, Line 150]

- Maximum voluntary contraction task is usually conducted for 5s (Stackhouse et al., 2001; Boettcher et al., 2008).

 

4) In results, I could not understand that the statistical analysis was done between which variables. The tables and figures are complicated to follow. The author talks about the regression model while they did not explain in the method section this model and its variables.

- As your recommendation, results part have been revised overall. Tables and Figures also have been revised overall (Table 2, Figure 2, Figure 3). The method of regression model also has been added in method section.

 

[Method, 2.4. Experimental design, Line 177-182]

[The polynomial regression analysis is used to predict the actual exerted force from the perceived exertion force (Equation 2) for male and female. Where yac represents the actual exerted force, parameters Bj represents the regression coefficient, and xper represents the perceived thumb force.]

 

Round 2

Reviewer 2 Report

Many will take issue with the casual use of "Work-related musculoskeletal disorders (WMSDs)" in the background. I encourage you to consult

"Musculoskeletal Disorders and the Workplace Low Back and Upper Extremities
National Research Council (US) and Institute of Medicine (US) Panel on Musculoskeletal Disorders and the Workplace. 

https://www.ncbi.nlm.nih.gov/books/NBK222440/ 

and see if you can explain that WMSDs include many muscle, tendon and nerve disorders and that "forceful exertions" have been identified as one work-related factor.

I take issue with the conclusion "the results of this study can provide an easy and accurate method of estimating the thumb force in the manufacturing field."

You have yet to demonstrate the accuracy and precision of this tool in the field and, based on my experience, these procedures are seldom as easy as they seem.  Anyway, that is up to the user to decide.

Author Response

Many will take issue with the casual use of "Work-related musculoskeletal disorders (WMSDs)" in the background. I encourage you to consult Musculoskeletal Disorders and the Workplace Low Back and Upper Extremities National Research Council (US) and Institute of Medicine (US) Panel on Musculoskeletal Disorders and the Workplace. https://www.ncbi.nlm.nih.gov/books/NBK222440/ and see if you can explain that WMSDs include many muscle, tendon and nerve disorders and that "forceful exertions" have been identified as one work-related factor.

 

==> Thanks for your valuable comments and a WMSDs reference. As far as I understand it, the causes of WMSDs for many diverse body parts (back, shoulder, elbow etc.), muscles and tissues were not only postures, repetitions but also forcefule exertions. The authors revised a sentence in Introduction as follows. 

[Rapid repetitive activities and overexertion of thumb (forceful exertions) in physiotherapy, sports, and assembly lines were reported as the leading causes of thumb injuries [3],[4].]

 

I take issue with the conclusion "the results of this study can provide an easy and accurate method of estimating the thumb force in the manufacturing field." You have yet to demonstrate the accuracy and precision of this tool in the field and, based on my experience, these procedures are seldom as easy as they seem.  Anyway, that is up to the user to decide.

==> Thanks for your comments. Authors agreed with some of reviewer's opinions. Sicne the accuracy and precision of this tool has not been verified in the current study, I would be better to rephrase the sentence as follows:

[The results of this study may provide an easy method of estimating the thumb force in the manufacturing field. Data from this study might also be used as a guideline for thumb pressing work which often occur in the industries such as automobile assembling lines.]

 

 

 

Reviewer 3 Report

The authors improve the manuscript, and I think it merits to publish in your journal. 

Author Response

The authors improve the manuscript, and I think it merits to publish in your journal.

==> Thank you so much.

Author Response File: Author Response.pdf