Oxidative Stress and Antioxidant Enzymes Activity after Cycling at Different Intensity and Duration
, Fatimah Ahmedy 1,3, Dayang Marshitah Pg Baharuddin 1,4 and Zainul Amiruddin Zakaria 2,5
Round 1
Reviewer 1 Report
The manuscript “Oxidative Stress and Antioxidant Enzymes Activity Following a Randomised Crossover Trials Indoor Cycling at Moderate to High Intensity for Short to Long Duration of Exercise Using Stationary Bike” by D. Maryama Ag. Daud et al. studied the effects of cycling on oxidative stress and antioxidant enzymes activity. For this, they measured several physiological indicators (e.g., MDA, SOD) in sedentary subjects after they performed indoor cycling at various strength and for different duration. The authors found that cycling did show effects on these physiological markers and provide health suggestions for sedentary adults accordingly.
This is a review of potential interest. The study is straightforward, and the results are clearly shown. Below are some of my suggestions that the authors might find worthwhile to consider:
1. The title is too long and contains too much detailed information. I am also not sure if the grammar is correct here. A more concise and high-level title should be used.
2. In lines 214-220, where the authors first describe results for MDA and CAT, references to tables and figures should be added.
3. In lines 225-226, there is no need to state explicitly that results are shown in table 3. This is redundant information which has already been shown through references to the table.
4. In lines 250-252, the authors state that “the percentage of SOD and AE … increased with exercise intensity”. If I understood correctly, Figures 4 and 5 show that SOD and AE actually decrease with exercise intensity.
5. To better illustrate the last point, maybe the authors could add average values for each exercise intensity in Figures 1-5.
6. In figures 1-5, the authors should indicate which of the values are significant. This will be very helpful for the readers to parse all the results.
Author Response
Response to Reviewer 1 Comments
Dear Reviewer, Thank you for the opportunity to respond to reviewers and revise our submission. We believe it is a stronger paper with these revisions incorporated. Please see the response to Reviewer comments below and revisions in text.
Point 1: The title is too long and contains too much detailed information. I am also not sure if the grammar is correct here. A more concise and high-level title should be used.
Oxidative Stress and Antioxidant Enzymes Activity Following a Randomised Crossover Trials Indoor Cycling at Moderate to High Intensity for Short to Long Duration of Exercise Using Stationary Bike
Response 1: The title has been shortened and revised: “Oxidative Stress and Antioxidant Enzymes Activity after Cycling at Different Intensity and Duration”.
Point 2: In lines 214-220, where the authors first describe results for MDA and CAT, references to tables and figures should be added.
Response 2: We have added a Table 3 at the end of each result description.
Point 3: In lines 225-226, there is no need to state explicitly that results are shown in table 3. This is redundant information which has already been shown through references to the table.
Response 3: We have removed the statement in lines 225-226. (in red)
Point 4: In lines 250-252, the authors state that “the percentage of SOD and AE … increased with exercise intensity”. If I understood correctly, Figures 4 and 5 show that SOD and AE actually decrease with exercise intensity.
Response 4: This statement has been revised for clarity and we believe this is better described. “Fig. 4 and Fig.5 showed the percentage changes of SOD and AE decreased with exercise duration but increased with exercise intensity.” Actually the result was described as SOD and AE decrease with exercise intensity (lines 246-247).
Point 5: To better illustrate the last point, maybe the authors could add average values for each exercise intensity in Figures 1-5. In figures 1-5, the authors should indicate which of the values are significant. This will be very helpful for the readers to parse all the results.
Response 5: Thank you for this suggestion. We have added the average values for each exercise intensity and indicate the significant values with **significantly different from 70% VO2 peak (p<0.05) in figures 1-5.
Author Response File: 
Author Response.docx
Reviewer 2 Report
First of all, I want to congratulate the authors for the study. In fact, the article reports an important study for the academic and scientific community.
Line 40 – the expression antioxidant enzymes activity ratio should be reformulated according the descriptors.
Line 68 – reference used? There is a final point missing.
Line 94 – There is a final point missing.
Line 95 - Materials and Methods - what kind of randomization was used in this study?
According to enhancing the quality and transparency of research, did you used some guidelines, like CONSORT 2010? This information is very important to the development of randomised trials and should be clarified.
Lines 113/114 – What statistical program was used to calculate the sample size?
Lines 175-180 – see spacing between lines.
Line 282 – locate the reference Radak Z et al.
In the article, the results of the present investigation and the importance for the academic and clinical community are clearly described. However, the limitations of this study were not identified, and it is essential be clarified.
Some bibliographic references used throughout the article are not recent (from the last 5 years). This option must be justified by the authors.
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 2 Comments
Dear Reviewer, Thank you for the opportunity to respond to reviewers and revise our submission. We believe it is a stronger paper with these revisions incorporated. Please see the response to Reviewer comments below and revisions in text.
Point 1: First of all, I want to congratulate the authors for the study. In fact, the article reports an important study for the academic and scientific community.
Response 1: Thank you for your review.
Point 2:
Line 40 – the expression antioxidant enzymes activity ratio should be reformulated according the descriptors.
Response 2: Thank you for your feedback. Line 40 was discussing about the imbalance between free radical and antioxidants. We have replaced the word pro-oxidants to free radicals.
Point 3: Line 68 – reference used? There is a final point missing.
Response 3: Thank you for this notation. This error has been corrected. (line 62).
Point 4: Line 94 – There is a final point missing.
Response 4: Thank you for this notation. We have revised (Line 91) to include the following “antioxidant enzymes activity”.
Point 5 and 6: Line 95 - Materials and Methods - what kind of randomization was used in this study?
Response 5 & 6: Thank you for the comments. These statements has been revised for clarity: “As the study's main objective was to determine the oxidative stress levels after cycling at different intensities and durations, this study used a crossover study design. Subjects underwent nine (9) exercise bouts with different intensities and durations, one after another in a random order following ; either the 50%VO2pk for 10-mins; 60%VO2pk for 10-mins; 70%VO2pk for 10-mins; 50%VO2pk for 20-mins; 60%VO2pk for 20-mins; 70%VO2pk for 20-mins; 50%VO2pk for 30-mins; 60%VO2pk for 30-mins; or 70%VO2pk for 30-mins. Subjects performed exercise at a constant predetermined work rate for each intensity throughout the duration without an increase in VO2. The exercises in this study were performed in a temperature-controlled laboratory between 18o to 20oC to ensure that the measured VO2 and HR for each exercise bout can be maintained. “
Point 6: According to enhancing the quality and transparency of research, did you used some guidelines, like CONSORT 2010? This information is very important to the development of randomised trials and should be clarified.
Response 6: the sequence of the nine (9) exercise bouts was in random order. However, we did not use CONSORT 2010 guidelines in this study. Thus, we have revised and omit the word randomization from the title and from lines 19, 83, 88.
Point 7: Lines 113/114 – What statistical program was used to calculate the sample size?
Response 7: The following statement in the statistical analysis section has been included: “Only 25 subjects completed the exercise program. In which using G*Power, this figure fulfilled the calculated sample size based on the power of 1−β = 0.95.” (lines 106-108).
Point 8: Lines 175-180 – see spacing between lines.
Response 8: We have removed the space.
Point 9: Line 282 – locate the reference Radak Z et al.
Response 9: Yes, we found the reference in the reference list.
Point 10: In the article, the results of the present investigation and the importance for the academic and clinical community are clearly described. However, the limitations of this study were not identified, and it is essential be clarified.
Response 10: Thank you for your feedback, we have expanded our study limitations (lines 426-434) and include the following in the discussion section. “Overall exercise intensity should not exceed 70% VO2pk for more than 20 minutes continuously. However, this was limited to acute changes in oxidative stress levels and antioxidant enzymes activity among healthy, sedentary young adult males. The chronic state of oxidative stress produced by exercise at a moderate intensity, not more than 70% VO2pk mediates the adaptation of antioxidant enzymes was not investigated. This study also does not examine the effect of post-exercise rest at different intensities and durations, which also contributes to oxidative stress levels. Another limitation of this study does not address the cycle efficiency factor which also contributes to oxygen consumption during exercise.”
Point 11: Some bibliographic references used throughout the article are not recent (from the last 5 years). This option must be justified by the authors.
Response 11: We have revised the reference list by removing and replacing with a recent reference if available. Nevertheless, some of the references especially regarding antioxidant enzymes activity and oxidative stress, we have to refer to the original resources.
Author Response File: Author Response.docx
Reviewer 3 Report
Grammatical and syntactical errors were detected, authors need to fix that. Methodology is not adequately described (section II). The information part is weak and cannot see how datasets are adequately used in this research. Results are not properly presented.
How authors performed evaluation? Did they use any benchmarks or human evaluators?
Author Response
Response to Reviewer 3 Comments
Dear Reviewer, Thank you for the opportunity to respond to reviewers and revise our submission. We believe it is a stronger paper with these revisions incorporated. Please see the response to Reviewer comments below and revisions in text.
Point 1: Grammatical and syntactical errors were detected, authors need to fix that.
Response 1: Thank you. This error has been corrected (title) and lines 62 and 91.
Point 2: Methodology is not adequately described (section II).
Response 2: We have revised the methodology (lines 159 – 168).
Point 3 The information part is weak and cannot see how datasets are adequately used in this research. Results are not properly presented.
Response 3: We have added the average values for each exercise intensity and indicate the significant values with **significantly different from 70% VO2 peak (p<0.05) in figures 1-5. We revised few statements lines 234-235 and lines 245-247. We add ANOVA analysis in Table 3 and a paragraph (lines 260-267) describing the repeated measures ANOVA analysis.
Point 4: How authors performed evaluation? Did they use any benchmarks or human evaluators?
Response 4: This study was only looking into the changes on the oxidative stress marker (malondialdehyde, MDA), and the responses of the antioxidant enzymes (catalase, CAT; glutathione peroxidase, GPx; superoxide dismutase, SOD). Since we only studied the oxidative stress as a physiological response and not pathological, we do not use any benchmarks or reference values for this study.
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
I am still looking for the answer for how authors evaluated their results. I understand if you are not using any benchmark. However, how can you confirm that these are accurate or relevant results?
Author Response
RESPONSE TO REVIEWER 3
Basically this study investigates the oxidative stress level at different cycling intensity and duration. “Oxidative Stress” is defined as “an imbalance between oxidants and antioxidants in favour of the oxidants, leading to a disruption of redox signalling and control and/or molecular damage”. In this study, the molecular damage was measured using MDA concentration. MDA is a lipid peroxidation product as described as an oxidative stress biomarkers in lines 124 -125 ). Increase in MDA concentration indicates increase in oxidative stress level. The MDA result was further supported with the main endogenous enzymatic antioxidant activity (SOD, CAT and GPx). Whereby each antioxidant enzyme demonstrate different response pattern after exercise at each intensity level and duration.
Author Response File: Author Response.docx
