A Comparison of the Validity of Three Exercise Tests for Estimating Maximal Oxygen Uptake in Korean Adults Aged 19–64 Years

Round 1

Reviewer 1 Report

First, I would like to acknowledge the opportunity to review this manuscript. My overall impression is that this article has serious flaws that preclude me from recommending a new revision. For example, the experimental design fails to describe accurately the procedures and the title is not fit with it. For example, the PACER test is not a submaximal test because it finishes when the subject is exhausted.

Author Response

Dear reviewer 

Thank you for reviewing our manuscript.

The PACER (20m shuttle run) test is conducted by the subject to the maximum level of their aerobic ability, but the measurement is sometimes terminated for various reasons such as speed and leg pain. The reviewer argues that the PACER test is not a submaximal exercise test, but based on several previous studies, we argue that this is a submaximal exercise test. Below are previous studies that have recognized the PACER test frame as the submaximal exercise test.

Noonan, V., & Dean, E. (2000). Submaximal exercise testing: clinical application and interpretation. Physical therapy, 80(8), 782-807

Duperly, J., Serrato, M., Forero, N. I., Jimenez-Mora, M. A., Mendivil, C. O., & Lobelo, F. (2020). Validation of Maximal, Submaximal, and Nonexercise Indirect VO2max Estimations at 2600 m Altitude. High altitude medicine & biology, 21(2), 135-143.

Scott, T. J., McLaren, S. J., Caia, J., & Kelly, V. G. (2018). The reliability and usefulness of an individualised submaximal shuttle run test in elite rugby league players. Science and Medicine in Football, 2(3), 184-190.

McNaughton, L., Hall, P., & Cooley, D. (1998). Validation of several methods of estimating maximal oxygen uptake in young men. Perceptual and motor skills, 87(2), 575-584.

Owen, C., Jones, P., & Comfort, P. (2017). The reliability of the submaximal version of the Yo-Yo intermittent recovery test in elite youth soccer. Journal of Trainology, 6(1), 31-34.

Reviewer 2 Report

General comments:

Dear Authors,

The article “A comparison of the validity of three submaximal exercise tests for estimating maximal oxygen uptake in Korean adults aged 19-64 years” is interesting, but several parts of the manuscript should be corrected. Development of reliable estimation tools for maximum oxygen consumption is important in the context of research especially older people who do not make the maximum effort. Thus, am in favor of accepting the article after corrections.

Specific comments:

Introduction:

The introduction is clearly described and fluently goes to next paragraphs. Please add appropriate information to enhance theoretical background.

Line 35 Using different protocols can lead to varied values of measured variables (VO2, HR, PPO,Vpeak) in the test using treadmill or cycle ergometer.

https://pubmed.ncbi.nlm.nih.gov/22959559/

https://pubmed.ncbi.nlm.nih.gov/30758163/

https://pubmed.ncbi.nlm.nih.gov/31623132/

Line 40-41 Not only expensive equipment. Please indicate the importance of submaximal tests (for example it is difficult to perform maximal effort during GXT by older participants). Maybe further in the line 69-71.

You should show estimated values of VO2max, SEE, CV from cited references.

Line 77-80 What is your hypothesis?

Materials and Methods

You can inform about the number of participants in the groups divided by age (19-30, 31-41 and next).

Line 120 Why did you not use Tanaka equation?

https://pubmed.ncbi.nlm.nih.gov/11153730/

https://pubmed.ncbi.nlm.nih.gov/29599724/

Line 121 (VCO₂/VO₂)

Line 125 Do not you think this is a significant measurement error?

Results

The results are clearly presented.

Discussion

Lines 267 – 268 Maybe participants could be signed as boys and girls? Males and females are stereotypically associated as adults.

Lines 299 – 304 You can add an argument concerning lack of added respiratory dead space during wearing a cloth mask. Other articles compared acute responses when ARDS was increased to 1200ml (https://pubmed.ncbi.nlm.nih.gov/33352863/) during high-intensity exercise sessions. A physiological explanation will increase the scientific value of the discussion. 

Lines 317 – 328 Add information about further research, eg. long-term training period when youth players wear a clothing mask during all training sessions.

Discussion

In the first paragraph show the most important results of your study, not only remembered the main goal.

The PACER test had the highest correlation used in this research. Compare with different tests used to estimate VO2 and give recommendations for further research to improve this equation.

Conslusions

Give only the most important.

Author Response

Dear reviewer

We would like to take this opportunity to express our sincere thanks to the reviewers who identified the sections of our manuscript that required correction or modification. In the following lines, we would like to respond your questions on a point-by-point basis. We putted numbers for your comments just for easy understanding. Revisions in the text are highlighted in red. We hope that the revised manuscript will now be deemed acceptable for publication in Applied & Sciences.

Reviewer(s)' Comments to Author:

The article “A comparison of the validity of three submaximal exercise tests for estimating maximal oxygen uptake in Korean adults aged 19-64 years” is interesting, but several parts of the manuscript should be corrected. Development of reliable estimation tools for maximum oxygen consumption is important in the context of research especially older people who do not make the maximum effort. Thus, am in favor of accepting the article after corrections.

Specific comments:

Introduction:

The introduction is clearly described and fluently goes to next paragraphs. Please add appropriate information to enhance theoretical background.

1. Line 35 Using different protocols can lead to varied values of measured variables (VO2, HR, PPO,Vpeak) in the test using treadmill or cycle ergometer.

https://pubmed.ncbi.nlm.nih.gov/22959559/

https://pubmed.ncbi.nlm.nih.gov/30758163/

https://pubmed.ncbi.nlm.nih.gov/31623132/

Response

We agree with your opinion that when the maximal oxygen intake was measured using a treadmill, the values of the measured variables vary depending on which protocol using it. Therefore, we measured maximal oxygen intake using Bruce protocol, which is frequently used in ordinary healthy adults. It mentioned in the method section.

2. Line 40-41 Not only expensive equipment. Please indicate the importance of submaximal tests (for example it is difficult to perform maximal effort during GXT by older participants). Maybe further in the line 69-71.

Response

We agree with your and revised our manuscript accordingly. The revised sentence is as follows.

“Furthermore, it is difficult to perform maximal effort during GXT by older people [8]”

3. You should show estimated values of VO2max, SEE, CV from cited references.

Response

Thanks for your review. We focused on the comparison between our study results and previous studies in the discussion section. In the discussion section, the correlation coefficient, standard error, and related variables of previous studies were mentioned. 

4. Line 77-80 What is your hypothesis?

Response

Thanks for your review. The hypothesis of our study is that "there will be a difference in validity between the three maximum oxygen intake prediction models." In addition, since this overlaps with the purpose of our study, we did not write a separate hypothesis in the introduction section.

5. Materials and Methods

You can inform about the number of participants in the groups divided by age (19-30, 31-41 and next).

Response

We completely agree with your review. We revised the table 1.

6. Line 120 Why did you not use Tanaka equation?

https://pubmed.ncbi.nlm.nih.gov/11153730/

https://pubmed.ncbi.nlm.nih.gov/29599724/

Response

We completely agree with your review. If the Tanaka equation had been used as your opinion, the level of study would have been higher, but unfortunately, the general equation (220 - age) was used. In the future, when estimating the maximal heart rate in our study, we will refer to the Tanaka equation. Thank you for the advice.

7. Line 121 (VCO2/VO2)

Response

It has been modified.

8. Line 125 Do not you think this is a significant measurement error?

Response

We completely agree with your review. There was a misunderstanding in writing English sentences. In our study, the important thing in measuring heart rate was to find the heart rate of the steady state. During Bruce protocol, the average heart rate for the last 10 seconds of each stage was recorded, and when the error in each heart rate for 10 seconds exceeded 5bpm, the median value was recorded. (This is to reduce the error of the average value).

The revised sentence is as follows.

“During treadmill test, the average heart rate for the last 10 seconds of each stage was recorded, and when the error in each heart rate for 10 seconds exceeded 5bpm, the median value was recorded.”

9. Results

The results are clearly presented.

Response

Thanks for your review.

10. Discussion

Lines 267 – 268 Maybe participants could be signed as boys and girls? Males and females are stereotypically associated as adults.

Response

It seems to be confused with other studies and our study. Please check it again.

11. Lines 299 – 304 You can add an argument concerning lack of added respiratory dead space during wearing a cloth mask. Other articles compared acute responses when ARDS was increased to 1200ml (https://pubmed.ncbi.nlm.nih.gov/33352863/) during high-intensity exercise sessions. A physiological explanation will increase the scientific value of the discussion.

Response

It seems to be confused with other studies and our study. Please check it again.

12. Lines 317 – 328 Add information about further research, eg. long-term training period when youth players wear a clothing mask during all training sessions.

Response

It seems to be confused with other studies and our study. Please check it again.

13. Discussion

In the first paragraph show the most important results of your study, not only remembered the main goal.

Response

The first paragraph of the discussion was revised.

14. The PACER test had the highest correlation used in this research. Compare with different tests used to estimate VO2 and give recommendations for further research to improve this equation.

Response

The following sentences were added.

“Finally, it is necessary to consider that predictors include height and weight in our study, but overweight may affect predictive models [41]. Therefore, to develop an accurate estimation model, additional studies are needed considering variables such as body fat ratio and muscle mass.”

14. Conslusions

Give only the most important.

Response

The sentence in the conclusion was moved to the discussion section.

Author Response File: Author Response.docx

Reviewer 3 Report

I read with great interest this well-written and well-designed study.

I have some comments:

• It would be very interesting to add (if available) data about smoking status, which is well-known to affect exercize capacity.
• Did authors estimate sample size? Please add it in data analysis section.
• I found several minor english errors throughout the paper. Please have a deep revision, possibly by a mother-tongue.
• This interesting data were obtained within a korean population, but these findings might be different when testing different races like caucasian or african, etc. Please address this in discussion section. 

Author Response

Dear reviewer

We would like to thank you for your constructive comments on our study. In the following lines, we would like to respond your questions on a point-by-point basis. We putted numbers for your comments just for easy understanding. Revisions in the text are highlighted in red. We hope that the revised manuscript will now be deemed acceptable for publication in Applied & Sciences.

Reviewer(s)' Comments to Author:

1. It would be very interesting to add (if available) data about smoking status, which is well-known to affect exercize capacity.

Response

We agree with your opinion. Unfortunately, the smoking status was not confirmed during the study. It should be considered in future studies. Thank you again for your advice.

2. Did authors estimate sample size? Please add it in data analysis section.

Response

We agree with your and revised our manuscript accordingly. The revised sentence is as follows.

“The required sample size was calculated using the G-power program (version 3.1 for window) based on the effect size of 0.15, the power value of 0.95, and 5 predictors in multiple regression analysis. The results indicated that 138 participants were required for our study.”

3. I found several minor english errors throughout the paper. Please have a deep revision, possibly by a mother-tongue.

Response

We have requested English correction from a verified company, but it seems that English correction has not been made completely. We will review it again.

4. This interesting data were obtained within a korean population, but these findings might be different when testing different races like caucasian or african, etc. Please address this in discussion section.

Response

We completely agree with your review. We added races issues as a limitation of our research in discussion.

Author Response File: Author Response.docx

Reviewer 4 Report

This manuscript compares the validity of three submaximal exercise tests (SMETs) and discusses practical predictive models for the VO2max in Korean adults.  This study is meaning and interesting. I recommend accepting this paper after addressing the following comments.

1. The main difference between this study and other similar researches should be further discussed to reveal the necessary of this study.
2. What is the novelty of this study?
3. The statisticalanalysis is too general to highlight the main contribution of this study.
4. What is the significance ofthe discussed practical predictive model in this study? And how to evaluate the feasibility and robustness of this proposed model?

Author Response

Dear reviewer

We would like to thank you for your constructive comments on our study. In the following lines, we would like to respond your questions on a point-by-point basis. We putted numbers for your comments just for easy understanding. Revisions in the text are highlighted in red. We hope that the revised manuscript will now be deemed acceptable for publication in Applied & Sciences.

Reviewer(s)' Comments to Author:

1. This manuscript compares the validity of three submaximal exercise tests (SMETs) and discusses practical predictive models for the VO2max in Korean adults.  This study is meaning and interesting. I recommend accepting this paper after addressing the following comments.

The main difference between this study and other similar researches should be further discussed to reveal the necessary of this study.

Response

We completely agree with your review. Most of the previous studies of the maximal oxygen intake estimation equation for Asians were conducted in a narrow age group between their 20s and 40s. However, our study is meaningful in that it was conducted on a wide range of age groups between 19 to 64 years. This was emphasized once again in the introduction.

2. What is the novelty of this study?

Response

Thanks for your review. The previous studies have compared the reliability and validity of the submaximal exercise test using the existing estimation equation or not actually measuring the maximal oxygen intake. The main difference of our study is that the maximal oxygen intake was measured in the same subjects on a large scale, and three submaximal exercise tests were performed to develop and compare estimation equations.

3. The statisticalanalysis is too general to highlight the main contribution of this study.

Response

Thanks for your review. All three measurement methods were effective in estimating the maximum oxygen intake, and rather than emphasizing one of them, all three measurements were effective. In the future, follow-up studies using other statistical analyses will be needed. In addition, among the results, the physical characteristics of the subjects were classified by age group and presented in a table 1.

4. What is the significance ofthe discussed practical predictive model in this study? And how to evaluate the feasibility and robustness of this proposed model?

Response

Thanks for your review. We completely agree with your opinion. Many people play the aerobic exercise for their health, but they actually fail to objectively evaluate their level of aerobic ability. Using the estimation equation of this study, it will be possible to maximize the effectiveness of exercise by receiving feedback on how much aerobic exercise has always improved one's aerobic ability. Moreover, the developed three predictive models in our study showed similar or higher levels of quality compared to conventional predictive models. Moreover, it has the advantage of being applicable to people of high age. Among the three predictive models, they will be able to evaluate their aerobic ability through an evaluation method suitable for their status or condition.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I read carefully the authors' reply regarding my concerns about the PACER test. They argued that is a submaximal test despite the test is designed to finish when exhaustion is achieved. Therefore, despite they provided additional references regarding the use of submaximal testing, I feel that calling "submaximal" a test that is performed till exhaustion is not precise. In my opinion, they should change this and additionally, explain better the PACER procedure. 

Author Response

Dear reviewer

Thank you for reviewing our study. I have considered your opinion once again and I respect your review. Unlike PACER test, treadmill test has different characteristics in that they only have to be performed within 10 minutes to estimate the maximal oxygen uptake. In addition, the step test ends within 3 minutes. Therefore, we deleted "maximal" from the title. In addition, a description of the pacer method was added.

The added sentence is as follows.

“The initial speed was 8.5 km/h and the speed was increased to 0.5 km/h per minute”

Thank you again for your review for the completeness of our study.

Sincerely,

Corresponding author; Kihyuk Lee

E-mail: [email protected]

Reviewer 4 Report

Author Response

Dear reviewer

Thank you again for your review for the completeness of our study.

Sincerely,

Corresponding author; Kihyuk Lee

E-mail: [email protected]