Acute Moderate-Intensity Aerobic Exercise under High PM_2.5 Levels Does Not Influence the Pulmonary Function and Lung Diffusion Capacity in Healthy Young Men

Round 1

Reviewer 1 Report

Title: Effect of moderate-intensity aerobic exercise under high PM2.5 levels on pulmonary function and lung diffusion capacity in young adults

Summary: The purpose of the manuscript under review was to

"investigate effects of aerobic exercise under high PM2.5 conditions on pulmonary function in young adults" (or to examine the effects of low and high PM2.5 levels on pulmonary function following aerobic moderate-intensity exercise?). Nine (small sample size; no sample size calculation) young men (inclusion and exclusion criteria were not fully described) performed treadmill running (moderate-intensity was controlled by HRpeak, which could vastly vary in terms of anaerobic threshold, AT) in both high and low PM2.5 conditions (uncontrolled setting!) by randomized crossover study design. Pulmonary function was assessed by spirometry and DLco at pre- and 1-h post-exercise (why 1-h post-exercise? Could the possible effects of exercise/PM2.5 exposure remain over 1-h?). The authors noted that FEV1 in low PM2.5 condition, but not in high PM2.5 condition, was increased after exercise. The authors also noted that DLco did not change after the exercise in both experimental conditions. The authors concluded that "aerobic exercise that significantly increases ventilation at high PM2.5 levels may offset its beneficial effects on the pulmonary function" (conclusions are still unclear! The study under review demonstrated that high PM2-5 levels might mitigate the increase in FEV1 post-moderate-intensity exercise).

General comments: The authors are commended for a well-written manuscript. The arguments for the study under review are timely and original. I believe, however, there are significant concerns and issues with the manuscript in its current form, and therefore, the document is, in my view, unsuitable for publication. All my comments about the investigation are included below. I hope you will find them to be constructive and helpful. 

Major Concerns: The primary concerns with the manuscript are presented below:

Introduction. The purpose of the manuscript under review should be revisited. The authors argued that this study aimed to "demonstrate the effect of acute moderate-intensity aerobic exercise on pulmonary function under high indoor PM2.5 conditions naturally formed by high outdoor PM2.5 levels". However, the study examined the effects of low and high PM2.5 levels on pulmonary function following aerobic moderate-intensity exercise. If my view is fail, please justify. However, the authors' hypothesis supports my interpretation since the "exposure to high PM2.5 conditions during the aerobic exercise would impair pulmonary function" was speculated. This incongruence between study purpose and hypothesis could be the reason for multiple methodological constraints (please see below).

Methods. Some sample characteristics were poorly reported. For example, were the participants in good health (and how was it assessed? PAR-Q?) or users of any supplement or medication that could affect their responses to exercise? Were they physically active (and how was it measured?) with a previous exercise/sports background? Description of participants' fitness level (VO2max) is, for example, of paramount importance (and could be easily estimated using Bruce's protocol data) to the reader. Lastly, how were the participants recruited? (flyers, social media, etc.). Were they paid?

Methods. The inclusion of sample size calculation is crucial for the reader. Is the actual sample (n = 9) enough to explore the hypotheses of the current investigation (I believe not!)? If not, the reduced sample size should be acknowledged as a limitation. Please insert the sample size calculation.

Methods. Minor information on study design is lacking - or incomplete. For example, how were the participants randomized (using a website such as randomization.org)? Was the GXT maximal or submaximal? How was peak heart rate (peakHR) defined (the highest 15-sec average HR value throughout the test?)? If data on test duration are available, why did the authors not estimate participants' VO2max? Please explain. 

Methods. Information with notable impact on the replication of findings is also absent - or incomplete. For example, how the authors artificially created both low and high PM2.5 conditions. Was a specially constructed chamber used? If not, as a researcher, how could I replicate both settings and find similar findings? Please explain and provide information on the validity of the used model for controlling PM2.5. Please also provide information on the validity and reliability of the PM2.5 measurements using the selected light-scattering laser photometer device. In addition, why did the authors decide to assess pulmonary function parameters 1-h post-exercise? Could the effects of exercise and/or PM2.5 exposure remain for 1-h? Please explain. Lastly, using 70%peakHR is problematic since most participants could exercise below the anaerobic threshold (AT), while others could be exercising above the AT. Exercise intensities below and above AT cause varied physiological responses, potentially affecting multiple parameters of pulmonary function (for a detailed review, see Poole et al., 2020). 

Methods/Results. The statistical analysis is very problematic. I believe adequate statistical procedures should be RM-ANOVA with post hoc corrections, where tempo (pre- and post-assessments of pulmonary function) and condition (low PM2.5 and high PM2.5) are the main factors. If the authors are not in line with my suggestion, please justify. Lastly, the authors informed that "changes in the body composition... at pre-exercise intervention between the second and third visits" were assessed. However, data on body composition were not reported in the Results section. Why? Please justify and explain why the assessment of body composition changes could be critical in the current study.

Conclusion. The authors concluded that "short-term exposure to high PM2.5 concentration during a moderate-intensity aerobic exercise session might play a negative role in pulmonary function even in healthy young men. Specifically, we observed a significant increase of FEV1 in low PM2.5 conditions at 1 hour after the exercise intervention." Why could an increase in FEV1 post-exercise be interpreted as unfavorable? Please justify. More importantly, I believe the correct interpretation of the current findings is that short-term PM2.5 exposure during exercise has minimal/negligible effects on pulmonary function in healthy young men. Why did the authors consider changes in FEV1 more important than lack of changes in multiple, measured pulmonary function parameters? Please explain.

Minor concerns.

L32. Insert "the" before "constituents."

L32. Insert "the" before "human."

L34. Replace "level" with "levels."

L37. Insert "an" before "outdoor."

L39. Remove "into" before "the indoor."

L42. Insert a comma before "and its."

L47. Insert a comma before "which."

L56. Remove "to" before "deeper" and insert "a" before "deeper"... "reach a deeper."

L62. Change "moderate intensity" with "moderate-intensity."

Author Response

We would like to thank the reviewers and the editorial office for their time and effort to provide the thoughtful comments and suggestions. We believe that the revised manuscript is much improved following the suggested revisions.

General comments: The authors are commended for a well-written manuscript. The arguments for the study under review are timely and original. I believe, however, there are significant concerns and issues with the manuscript in its current form, and therefore, the document is, in my view, unsuitable for publication. All my comments about the investigation are included below. I hope you will find them to be constructive and helpful.

Introduction. The purpose of the manuscript under review should be revisited. The authors argued that this study aimed to "demonstrate the effect of acute moderate-intensity aerobic exercise on pulmonary function under high indoor PM2.5 conditions naturally formed by high outdoor PM2.5 levels". However, the study examined the effects of low and high PM2.5 levels on pulmonary function following aerobic moderate-intensity exercise. If my view is fail, please justify. However, the authors' hypothesis supports my interpretation since the "exposure to high PM2.5 conditions during the aerobic exercise would impair pulmonary function" was speculated. This incongruence between study purpose and hypothesis could be the reason for multiple methodological constraints (please see below).

Response:

   Thank you for the comments. It is correct that our study’s purpose and hypothesis were focused on demonstrating the effect of acute aerobic exercise on pulmonary function in high PM2.5 conditions. However, we thought showing the data acquired only in high PM2.5 conditions would be hard to understand the effect of high PM2.5 concentration on pulmonary function during the same exercise because we are not sure about the effect of better PM2.5 conditions (i.e., usual indoor gym environment) on pulmonary function with the same experimental settings. Thus, we applied the same protocol in low PM2.5 conditions as a control. We understand and agree with your comments. Thus, we changed the purpose, hypothesis, and statistical analysis method to RM-ANOVA to compare the difference in responses between the low PM2.5 and the high PM2.5 condition. Based on the RM-ANOVA results, we in part corrected our study result, discussion, and conclusion. Absolutely, we also changed our manuscript title.

Methods. Some sample characteristics were poorly reported. For example, were the participants in good health (and how was it assessed? PAR-Q?) or users of any supplement or medication that could affect their responses to exercise? Were they physically active (and how was it measured?) with a previous exercise/sports background? Description of participants' fitness level (VO2max) is, for example, of paramount importance (and could be easily estimated using Bruce's protocol data) to the reader. Lastly, how were the participants recruited? (flyers, social media, etc.). Were they paid?

Response:

   Thank you for your constructive comments. We checked their health status by asking them when they visited to sign an informed consent form, and all participants did not take any supplements and/or medicines that might influence exercise responses to cardiovascular and pulmonary function. Unfortunately, we did not measure their physical activity. However, we could confirm they are recreationally active through interviews and with the VO2peak value (Participants’ average VO2peak: 55.05 ml/min/kg). We added this information in Line 71 - 72 and Table 1.

   All participants were recruited by word of mouth at Incheon National University. Even though participants did not obtain compensation after finishing the study participation, they obtained their cardiovascular and pulmonary health information by participating in this study. All measurements that participants received throughout the study cost approximately US$ 450 in clinics and IRB approved providing the health information of cardiovascular and pulmonary function to participants instead of monetary reward.

Methods. The inclusion of sample size calculation is crucial for the reader. Is the actual sample (n = 9) enough to explore the hypotheses of the current investigation (I believe not!)? If not, the reduced sample size should be acknowledged as a limitation. Please insert the sample size calculation.

Response:

   We understand your concern about the sample size. Frankly, the small sample size is one of our study limitations, and we already mentioned it in the discussion section (Line 246- 249). Due to the small sample size, this study might not draw firm (strong) conclusions. Thus, we made very cautious conclusions based on the results of this study. In addition, one of our study purposes was to investigate feasibility on whether we could conduct this type of research study in a laboratory setting with ambient air without artificial air quality manipulation.

Methods. Minor information on study design is lacking - or incomplete. For example, how were the participants randomized (using a website such as randomization.org)? Was the GXT maximal or submaximal? How was peak heart rate (peakHR) defined (the highest 15-sec average HR value throughout the test?)? If data on test duration are available, why did the authors not estimate participants' VO2max? Please explain.

Response:

   Since we could not manipulate the high and low PM2.5 conditions with the ambient air, all visits were decided by daily weather conditions when participants were scheduled for the visit. We asked our participants for their available days to visit our lab for the next week every Friday and proceeded with the planned visits when the ambient air condition (either high or low PM2.5 condition) and participants’ availability were matched. Therefore, the second and third visits were assigned by the daily weather and participants’ availability. Consequently, four participants performed their second visit in low PM2.5 conditions and five participants finished their second visit in high PM2.5 conditions (Line 90 - 91).

   We performed a maximal GXT and added the data in Table 1 and added the associated explanation about how we define the peak oxygen consumption and peak heart rate in Line 79 - 86.

Methods. Information with notable impact on the replication of findings is also absent – or incomplete. For example, how the authors artificially created both low and high PM2.5 conditions. Was a specially constructed chamber used? If not, as a researcher, how could I replicate both settings and find similar findings? Please explain and provide information on the validity of the used model for controlling PM2.5. Please also provide information on the validity and reliability of the PM2.5 measurements using the selected light-scattering laser photometer device. In addition, why did the authors decide to assess pulmonary function parameters 1-h post-exercise? Could the effects of exercise and/or PM2.5 exposure remain for 1-h? Please explain. Lastly, using 70%peakHR is problematic since most participants could exercise below the anaerobic threshold (AT), while others could be exercising above the AT. Exercise intensities below and above AT cause varied physiological responses, potentially affecting multiple parameters of pulmonary function (for a detailed review, see Poole et al., 2020).

Response:

   Thanks for your comment. We conducted this study under the naturally formed PM2.5 environment from outdoor ambient air without any environmental manipulation. Because of our unique local environmental conditions, other researchers from a different country or even a different county in Korea cannot replicate our study with exactly same PM2.5 constituents and concentrations. However, other labs may conduct similar studies under similar PM2.5 concentrations in indoor spaces or environmental chambers. We input this information in Line 257 – 262 as a limitation.

   SIDEPAK^TM AM520, a light-scattering laser photometer device, is a validated, reliable device [1]. It produced reliable results (R² = 0.82) when compared to a standard device (BAM 1020, Beta Ray Attenuation Monitor 1020, and MetOne Instruments).

   Since we conducted other physiological measurements, we could only assess pulmonary function at 1-hour post-exercise and not immediately after the exercise intervention. Previous studies showed no changes of pulmonary function immediately after PM2.5 exposure and two studies found decreased pulmonary function at 1-hour post-exercise or exposure in a polluted environment. Based on these findings, we assumed that PM2.5 inhalation might not rapidly affect pulmonary function and timing will be the factor for assessing responses of pulmonary function after PM2.5 exposure. Therefore, we determined to measure pulmonary function at 1-hour post-exercise after performing other physiological measurements. We briefly mentioned factors that may affect inconsistent findings in the discussion (Line 199 – 202, 218 - 220).

   Our exercise intervention protocol followed the American College of Sports Medicine’s guidelines which recommended performing at least 30 minutes per day of moderate-intensity aerobic exercise for most adults [2]. However, we agree with your opinion about different physiological responses to exercise intensities. Since individuals will have different lactate threshold (LT), our intervention might be above LT for some participants. This will increase ventilation and induce different response of pulmonary function from the exercise. We appreciate your opinion and will consider LT for next study’s exercise intervention protocol. Additionally, we added this information in Line 249 - 254.

Conclusion. The authors concluded that "short-term exposure to high PM2.5 concentration during a moderate-intensity aerobic exercise session might play a negative role in pulmonary function even in healthy young men. Specifically, we observed a significant increase of FEV1 in low PM2.5 conditions at 1 hour after the exercise intervention." Why could an increase in FEV1 post-exercise be interpreted as unfavorable? Please justify. More importantly, I believe the correct interpretation of the current findings is that short-term PM2.5 exposure during exercise has minimal/negligible effects on pulmonary function in healthy young men. Why did the authors consider changes in FEV1 more important than lack of changes in multiple, measured pulmonary function parameters? Please explain.

Response:

   Thanks for your comment. After changing the statistical analysis method, we could not find any significant difference in pulmonary function responses after performing exercise in between high and low PM2.5 conditions. Consistent with our current results, we rewrite our results, discussion, and conclusion and even title.

   However, FEV1 is an important clinical index that describes the degree of airway obstruction caused by asthma. A previous study demonstrated that low FEV1 is a predictor of overall and cardiovascular mortality but not FVC [3]. Moreover, FEV1 has shown to be a stronger predictor than FVC for all-cause mortality in COPD patients [4]. Therefore, we assumed that demonstrating FEV1 changes by PM2.5 exposure would be important information to elucidate the effect of PM2.5 on pulmonary function.

Minor concerns.

L32. Insert "the" before "constituents."

L32. Insert "the" before "human."

L34. Replace "level" with "levels."

L37. Insert "an" before "outdoor."

L39. Remove "into" before "the indoor."

L42. Insert a comma before "and its."

L47. Insert a comma before "which."

L56. Remove "to" before "deeper" and insert "a" before "deeper"... "reach a deeper."

L62. Change "moderate intensity" with "moderate-intensity."

Response:

   Consistent with your suggestion, we revised all the above concerns. Thank you.

References

1. Stauffer, D.A.; Autenrieth, D.A.; Hart, J.F.; Capoccia, S. Control of wildfire-sourced PM2. 5 in an office setting using a commercially available portable air cleaner. Journal of Occupational and Environmental Hygiene 2020, 17, 109-120.
2. Garber, C.E.; Blissmer, B.; Deschenes, M.R.; Franklin, B.A.; Lamonte, M.J.; Lee, I.-M.; Nieman, D.C.; Swain, D.P. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Medicine and science in sports and exercise 2011, 43, 1334-1359.
3. Menezes, A.M.B.; Pérez-Padilla, R.; Wehrmeister, F.C.; Lopez-Varela, M.V.; Muiño, A.; Valdivia, G.; Lisboa, C.; Jardim, J.R.B.; De Oca, M.M.; Talamo, C. FEV1 is a better predictor of mortality than FVC: the PLATINO cohort study. PLoS One 2014, 9, e109732.
4. Bikov, A.; Lange, P.; Anderson, J.A.; Brook, R.D.; Calverley, P.M.; Celli, B.R.; Cowans, N.J.; Crim, C.; Dixon, I.J.; Martinez, F.J. FEV1 is a stronger mortality predictor than FVC in patients with moderate COPD and with an increased risk for cardiovascular disease. International journal of chronic obstructive pulmonary disease 2020, 15, 1135.

Reviewer 2 Report

To the Authors

The study APPLSCI-1862782 investigated the acute effect of moderate-intensity aerobic exercise on pulmonary function between two conditions with low and high PM2.5 concentration in young healthy individuals. They concluded that moderate-intensity aerobic exercise increased only FEV1 in the low PM2.5 concentration and there was no effect on diffusing capacity for carbon monoxide in both conditions. The study is well-designed and nicely executed. There are, however, a few data interpretational issues that authors need to clarify and subsequently address in their manuscript.

Major Points

The study is limited by the following major concerns:

1. The rationale of this study is unclear.

2. The description of the experimental protocol and procedures are not so clear.

3. Practical consideration was not highlighted.

Specific Points

The following points need to be addressed:

Abstract

Page 1, Lines 16-17: ‘Regular aerobic exercise improves pulmonary function.’ Aerobic exercise training has been demonstrated that improve ventilatory response during exercise and only occasionally could improve pulmonary function. Authors should provide more information on what exactly they mean. Did they mean pulmonary function at rest or/and during exercise?

Introduction

The authors have provided a good rationale to test the well-defined study hypothesis. However, the authors should provide more information on the positive effect of acute aerobic exercise on pulmonary function in healthy individuals as the research studies do not all agree with each other and the participants of this study are healthy. What are the practical considerations of this study?

Materials and Methods

Participants

Authors should provide data to justify that the sample size was adequate to detect differences between conditions as the number of participants is small

Study Design

Page 2, Lines 79-80: ‘In the initial visit, the participants performed a graded exercise test with a modified Bruce protocol to assess their peak heart rate (HRpeak).’ Authors should provide either a reference or information on the exercise protocol assessment.

Did the authors assess the ventilatory response or/and pulmonary function (such as flow-volume loops) during moderate-intensity aerobic exercise? It would be very interesting to investigate it during exercise in these two conditions.

Page 3, Line 99: ‘Height, weight and body composition’ Authors should replace the title of this paragraph with ‘Anthropometric characteristics. Furthermore, used body mass instead of weight throughout the manuscript.

PM2.5 concentration

Authors should provide more information on PM2.5 concentration between low and high concentrations. In other words, authors should define the two conditions.

What was the duration of exposure to the high and low PM2.5 concentrations before the start of the exercise? The level of PM2.5 concentrations are maintained consistently during the exercise?

Pulmonary function

Which is the interclass correlation coefficient (ICC) for test-retest reliability for pulmonary function evaluation?

Results

Page 3, Line 132: Table 1 Authors did not provide information on how the BMI was calculated in the materials and methods section.

Discussion

It is well written without raising major concerns.

Author Response

We would like to thank the reviewers and the editorial office for their time and effort to provide the thoughtful comments and suggestions. We believe that the revised manuscript is much improved following the suggested revisions.

Major Points

The study is limited by the following major concerns:

1. The rationale of this study is unclear.
2. The description of the experimental protocol and procedures are not so clear.
3. Practical consideration was not highlighted.

Responses:

   We revised last paragraph of introduction to clarify our study’s rationale and consideration. Also, consistent with you concern, we added more detailed information in methods to make them clear.

Specific Points

The following points need to be addressed:

Abstract

Page 1, Lines 16-17: ‘Regular aerobic exercise improves pulmonary function.’ Aerobic exercise training has been demonstrated that improve ventilatory response during exercise and only occasionally could improve pulmonary function. Authors should provide more information on what exactly they mean. Did they mean pulmonary function at rest or/and during exercise?

Responses:

   Thank you for your precious comment. Aerobic exercise improves pulmonary function not only in clinical populations but also in healthy individuals at rest after the planned exercise training [1-3]. We revised the sentences to improve the clarity (Line 16-17).

Introduction

The authors have provided a good rationale to test the well-defined study hypothesis. However, the authors should provide more information on the positive effect of acute aerobic exercise on pulmonary function in healthy individuals as the research studies do not all agree with each other, and the participants of this study are healthy. What are the practical considerations of this study?

Response:

   Performing aerobic exercise has been demonstrated to enhance pulmonary function even in healthy individuals [1,2,4,5]. However, previous findings investigating the effect of aerobic exercise on pulmonary function in high PM2.5 conditions are still controversial [6-12]. In this study, we tried to investigate responses of pulmonary function parameters to acute aerobic exercise in high and low PM2.5 environments. Air pollution is becoming a severe global concern due to its negative effect on the human cardiopulmonary system. Augmented PM2.5 concentrations are related to increased mortality of cardiovascular and respiratory diseases [13-15]. Although aerobic exercise is a well-known strategy to decrease the risk of chronic diseases (i.e., cardiovascular, neurological, respiratory diseases, and cancer), most aerobic exercises are performed in outdoor environments such as running, walking, and cycling. Exercising outdoors will likely lead to exposure to air pollution and inhale more air pollutants because of increased minute ventilation during exercise. Thus, we conducted this study to demonstrate the effect of aerobic exercise on pulmonary function in polluted air condition. Additionally, we used indoor PM2.5, penetrated from outdoor ambient air, to emphasize that the influx of ambient air can negatively affect indoor air quality. We hope our results can be used as scientific support for prescribing a safe exercise protocol under severe air conditions to improve and/or protect pulmonary function in both healthy and clinical populations.

Materials and Methods

Participants

Authors should provide data to justify that the sample size was adequate to detect differences between conditions as the number of participants is small

Response:

   Frankly, the small sample size is one of our study limitations, and we already mentioned about it in the discussion section (Line 246 - 249). Based on the effect sizes of FEV1/FVC and FVC acquired from our study, 13 and 200 participants had to be recruited to meet 80% power for sample size respectively. Frankly, it was very difficult to match the PM2.5 conditions with participants’ availability and to complete all visits with our current sample size because we performed our study procedures under indoor PM2.5 concentrations acquired by naturally formed ambient PM2.5.

   Due to the small sample size, this study might not draw firm (strong) conclusions. Thus, we made very cautious conclusions based on the results of this study. In addition, one of our study purposes was to investigate whether we could conduct this type of research study in a laboratory setting with ambient air without artificial air quality manipulation (feasibility test).

Study Design

Page 2, Lines 79-80: ‘In the initial visit, the participants performed a graded exercise test with a modified Bruce protocol to assess their peak heart rate (HRpeak).’ Authors should provide either a reference or information on the exercise protocol assessment.

Did the authors assess the ventilatory response or/and pulmonary function (such as flow-volume loops) during moderate-intensity aerobic exercise? It would be very interesting to investigate it during exercise in these two conditions.

Response:
   Thank you for your opinion. We added the reference for the modified Bruce protocol.  Unfortunately, we only measured pulmonary function before and at 1-hour post-exercise. It would be a fascinating study to measure ventilatory or pulmonary function during exercise. I hope we can conduct the measurements in our future study.

Page 3, Line 99: ‘Height, weight and body composition’ Authors should replace the title of this paragraph with ‘Anthropometric characteristics. Furthermore, used body mass instead of weight throughout the manuscript.

Response:
   Thanks much for your comments. We revised them based on your feedback.

PM2.5 concentration

Authors should provide more information on PM2.5 concentration between low and high concentrations. In other words, authors should define the two conditions.

What was the duration of exposure to the high and low PM2.5 concentrations before the start of the exercise? The level of PM2.5 concentrations are maintained consistently during the exercise?

Response:

   Thank you for your comments. We have added the associated information on PM2.5 concentration in Line 158 - 163.

   We guess that the duration of exposure to the high and low PM2.5 concentrations before the start of the exercise was varied with each participant because of differences in the distances between our participant’s living place and our laboratory, and in the ways to get to our laboratory. Unfortunately, we could not control their moving distance and way to get to our laboratory. However, participants were guided to wear masks to protect against exposure to PM2.5 and minimize the unnecessary exposure to PM2.5 when they were on the way to our laboratory. Additionally, we placed an air purifier in our lab where we assessed baseline and post-exercise pulmonary function to control air quality while measuring main dependent variables. We could not maintain the constant PM2.5 concentration during the aerobic exercise because it is naturally formed by outside ambient air condition. However, we closed all windows and doors in the exercise room to reduce the variation of PM2.5 concentration during the exercise. Throughout the study, we were able to have enough PM2.5 concentrations as we planned for high PM2.5 condition which is higher than the recommended U.S National Ambient Air Quality Standard. We input detailed information about PM2.5 concentration in the result section (Line 158 – 161). To give more information about PM2.5 concentrations, we added minimum and maximum PM2.5 concentrations for each condition in Table 2.

Pulmonary function

Which is the interclass correlation coefficient (ICC) for test-retest reliability for pulmonary function evaluation?

Response:

   Instead of ICC, we added the information about the day-to-day coefficient of variation for each pulmonary function variables (Line 129 - 130).

Results

Page 3, Line 132: Table 1 Authors did not provide information on how the BMI was calculated in the materials and methods section.

Response:

   Thank you for the suggestion. We have added the information in method 2.4. Height, weight, and body composition (Line 114 - 115).

References

1. Angane, E.Y.; Navare, A.A. Effects of aerobic exercise on pulmonary function tests in healthy adults. International J Research in Medical Sciences 2017, 4, 2059-2063.
2. Munibuddin, A.; Khan, S.; Choudhari, S.; Doiphode, R. Effect of traditional aerobic exercises versus sprint interval training on pulmonary function tests in young sedentary males: a randomised controlled trial. Journal of clinical and diagnostic research: JCDR 2013, 7, 1890.
3. Hansen, E.S.H.; Pitzner-Fabricius, A.; Toennesen, L.L.; Rasmusen, H.K.; Hostrup, M.; Hellsten, Y.; Backer, V.; Henriksen, M. Effect of aerobic exercise training on asthma in adults: a systematic review and meta-analysis. Eur Respir J 2020, 56, doi:10.1183/13993003.00146-2020.
4. Gupt, A.M.; Kumar, M.; Sharma, R.K.; Misra, R.; Gup, A. Effect of moderate aerobic exercise training on pulmonary functions and Its correlation with the antioxidant status. National Journal of Medical Research 2015, 5, 136-139.
5. Rawashdeh, A.; Alnawaiseh, N. The effect of high-intensity aerobic exercise on the pulmonary function among inactive male individuals. Biomedical and Pharmacology Journal 2018, 11, 735-741.
6. Giles, L.V.; Carlsten, C.; Koehle, M.S. The pulmonary and autonomic effects of high-intensity and low-intensity exercise in diesel exhaust. Environ Health 2018, 17, 87, doi:10.1186/s12940-018-0434-6.
7. Gong, H.; Linn, W.S.; Clark, K.W.; Anderson, K.R.; Sioutas, C.; Alexis, N.E.; Cascio, W.E.; Devlin, R.B. Exposures of healthy and asthmatic volunteers to concentrated ambient ultrafine particles in los angeles. Inhalation Toxicology 2008, 20, 533-545, doi:10.1080/08958370801911340.
8. Park, H.Y.; Gilbreath, S.; Barakatt, E. Respiratory outcomes of ultrafine particulate matter (UFPM) as a surrogate measure of near-roadway exposures among bicyclists. Environ Health-Glob 2017, 16, doi:10.1186/s12940-017-0212-x.
9. Sinharay, R.; Gong, J.; Barratt, B.; Ohman-Strickland, P.; Ernst, S.; Kelly, F.J.; Zhang, J.J.; Collins, P.; Cullinan, P.; Chung, K.F. Respiratory and cardiovascular responses to walking down a traffic-polluted road compared with walking in a traffic-free area in participants aged 60 years and older with chronic lung or heart disease and age-matched healthy controls: a randomised, crossover study. Lancet 2018, 391, 339-349, doi:10.1016/S0140-6736(17)32643-0.
10. Wagner, D.R.; Brandley, D.C. Exercise in Thermal Inversions: PM2.5 Air Pollution Effects on Pulmonary Function and Aerobic Performance. Wilderness Environ Med 2020, 31, 16-22, doi:10.1016/j.wem.2019.10.005.
11. Wagner, D.R.; Clark, N.W. Effects of ambient particulate matter on aerobic exercise performance. J Exerc Sci Fit 2018, 16, 12-15, doi:10.1016/j.jesf.2018.01.002.
12. Wyatt, L.H.; Devlin, R.B.; Rappold, A.G.; Case, M.W.; Diaz-Sanchez, D. Low levels of fine particulate matter increase vascular damage and reduce pulmonary function in young healthy adults. Part Fibre Toxicol 2020, 17, 58, doi:10.1186/s12989-020-00389-5.
13. Ostro, B.; Broadwin, R.; Green, S.; Feng, W.-Y.; Lipsett, M. Fine particulate air pollution and mortality in nine California counties: results from CALFINE. Environmental health perspectives 2006, 114, 29-33.
14. Schwartz, J.; Dockery, D.W.; Neas, L.M. Is daily mortality associated specifically with fine particles? Journal of the Air & Waste Management Association 1996, 46, 927-939.
15. Brook, R.D.; Rajagopalan, S.; Pope, C.A., 3rd; Brook, J.R.; Bhatnagar, A.; Diez-Roux, A.V.; Holguin, F.; Hong, Y.; Luepker, R.V.; Mittleman, M.A.; et al. Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association. Circulation 2010, 121, 2331-2378, doi:10.1161/CIR.0b013e3181dbece1.

Round 2

Reviewer 1 Report

The authors are commended for an interesting manuscript. All my suggestions about the manuscript were taken into account by the authors, and therefore the document is, in my view, suitable for publication.

Author Response

Other authors and I are deeply appreciated on your time and effort for making this manuscript improved and published. Thank you! 

Reviewer 2 Report

The authors have provided a thorough revision of the manuscript which has been substantially improved. However, they should pay attention to the above

 Title

Please change the title to ‘Acute Moderate-Intensity Aerobic Exercise Under 2 High PM2.5 Levels Does not Influence Pulmonary Function and Lung Diffusion Capacity in Healthy Young Men’

Abstract

Aerobic exercise improves pulmonary function only in high-level athletes of specific sports!!! Authors should be more consistent throughout the manuscript.

Introduction Lines 58-59: Authors should pay attention to pulmonary function and ventilatory response which is totally different. Aerobic exercise may improve the ventilatory response during exercise but occasionally improves pulmonary function in healthy individuals.

 Methods

It is a major limitation that PM2.5 was not kept constant throughout the intervention. Authors should be mentioned in the limitation section.

Authors should provide information about the duration of exposure at the baseline before the start of the exercise. 

Author Response

Responses to Reviewer (#2)’s Comments

The authors have provided a thorough revision of the manuscript which has been substantially improved. However, they should pay attention to the above

Answer) We are deeply appreciated on your time and effort for making this manuscript improved and suitable for publication. We did our best to prepare our responses to your comments. Hope that you are satisfied with our answers and explanations.

Title

Please change the title to ‘Acute Moderate-Intensity Aerobic Exercise Under 2 High PM2.5 Levels Does not Influence Pulmonary Function and Lung Diffusion Capacity in Healthy Young Men’

Answer) Thanks much for your suggestion. Our study design included both high (unhealthy, bad) and low (good) PM2.5 concentrations to investigate the acute effect of moderate-intensity aerobic exercise on pulmonary function and lung diffusion capacity under high PM2.5 conditions in comparison with low PM2.5 conditions. Thus, we think that our title is more suitable for our study purpose and hypothesis than your suggested title. We seek your generous understanding.

Abstract

Aerobic exercise improves pulmonary function only in high-level athletes of specific sports!!! Authors should be more consistent throughout the manuscript.

Answer) We regret that the expressions we have written are not unclear and the information we have provided is insufficient. Previous findings present that aerobic exercise has also improved pulmonary function in asthmatic patients and even healthy individuals [1-4]. Thus, we corrected the associated sentence to clarify its meaning. Please refer to the line 16-17.   

Introduction Lines 58-59: Authors should pay attention to pulmonary function and ventilatory response which is totally different. Aerobic exercise may improve the ventilatory response during exercise but occasionally improves pulmonary function in healthy individuals.

Answer) We are appreciated on your careful suggestion. To enhance its clarity, we have corrected the sentence in line 59-62.

Methods

It is a major limitation that PM2.5 was not kept constant throughout the intervention. Authors should be mentioned in the limitation section.

Answer) Thanks much for your suggestion. We have added the above information between line 247 and 250 as one of study limitations in the discussion section.

Authors should provide information about the duration of exposure at the baseline before the start of the exercise.

Answer) Thank you for your valuable suggestion. Baseline measurements took approximately 1.5 hours in both second and third visits since we measured other physiological parameters which are not included in this manuscript. During the baseline measurements at pre- and post-exercise, two air purifiers with HEPA filters were operated at the measurement room in our laboratory to minimize the effect of unnecessary PM2.5 exposure on pulmonary function and lung diffusion capacity parameters. Unfortunately, we could not measure PM2.5 concentrations with the same light-scattering laser photometer devices, but we continuously checked through the screen of the air purifiers that the PM2.5 concentrations were lower than 5 μg/m³. We have briefly added this information in the method section (Line 95 - 98). Moreover, we have also added a study limitation that study participants, despite wearing a mask, may have been exposed to different levels of PM2.5 while on the way to our laboratory because their residence and the distance and way to reach the laboratory were different (Line 236 – 239).

References

1. Angane, E.Y.; Navare, A.A. Effects of aerobic exercise on pulmonary function tests in healthy adults. International J Research in Medical Sciences 2017, 4, 2059-2063.
2. Giles, L.V.; Carlsten, C.; Koehle, M.S. The effect of pre-exercise diesel exhaust exposure on cycling performance and cardio-respiratory variables. Inhal Toxicol 2012, 24, 783-789, doi:10.3109/08958378.2012.717649.
3. Hansen, E.S.H.; Pitzner-Fabricius, A.; Toennesen, L.L.; Rasmusen, H.K.; Hostrup, M.; Hellsten, Y.; Backer, V.; Henriksen, M. Effect of aerobic exercise training on asthma in adults: a systematic review and meta-analysis. Eur Respir J 2020, 56, doi:10.1183/13993003.00146-2020.
4. Munibuddin, A.; Khan, S.; Choudhari, S.; Doiphode, R. Effect of traditional aerobic exercises versus sprint interval training on pulmonary function tests in young sedentary males: a randomised controlled trial. Journal of clinical and diagnostic research: JCDR 2013, 7, 1890.

Author Response File: Author Response.docx