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The latest revision has adequately addressed the concerns of the reviewer, accordingly, the manuscript is ready for publication.
[# PeerJ Staff Note - this decision was reviewed and approved by Mike Climstein, a PeerJ Section Editor covering this Section #]
Dear authors,
The second round of revision based on the reviewers' comments was adequate. The mayor issues regarding methodological content have been successfully revised and resolved.
Kind regards,
No comment
No comment
The reviewer are satisfied with some aspect of the changes to the manuscript. However, there are still outstanding issues with regards to methodology, in particular the use of sub-group analyses. Please take care to address this point directly in your revised manuscript.
Dear authors,
The revision of the manuscript based on the reviewers' comments was adequate. However, there are comments that remain to be addressed.
The meta-analytic approach of the systematic review, since it has subgroups, must include a statistical analysis to test for between-subgroup differences. Please, describe in the methods, and execute a statistical analysis of subgroups to test the effect of belonging to one group or the other (e.g., >10 weeks vs. < 10 weeks, males vs females, …). These results can be reported in Table 2 showing the number of effect sizes and volunteers in each subgroup, the within-group effect, and the between-group differences.
Thereafter, all results and interpretations throughout the manuscript should be based on such subgroup analyses.
The subgroup analysis could also be performed to test the effect (or non-effect) of conducting aerobic and resistance training on the same day or on alternate days, using the studies included in the meta-analysis.
The specific methodology used in the meta-analysis should be reported in the appropriate methods section, rather than in the results.
There is still no method used to assess the certainty (or confidence) in the body of evidence for each outcome (https://doi.org/10.1136/bmj.39489.470347.ad).
Table 1: include the specific model for each kit used. E.g., BioVendor® (Cat. No.: EEL-H6120).
L87-91: rewrite for a better interpretation of the cited articles and consistency with the preceding paragraph.
L98: replace "studies" by "systematic review and meta-analysis".
L235: cite studies.
L374: the method in the study was ELISA.
No comment
No comment
Dear Authors and Editors,
I thank you the authors for their efforts. Some points have been addressed, I have few other points. Feel free to come back to me whenever you would like to.
Line 50: please revise the first paragraph of the introduction, it seems redundant how obesity topic is explained, please link the new first sentence with the rest of the manuscript.
Line 103: authors should be aware that even if there are no mesh terms for each term, mesh should be used for the available terms (e.g., exercise) and search should be performed once only at one time point. Methodologically, your approach was not correct.
Line 195: if a 4-week training is included, this should have been stated in the protocol a priori, it can not be added/amended later based on findings. In addition, if a 4-w is included, then the title needs amendments as chronic refers to > 8 weeks. I suggest short- and long-term effects…
Line 328: in regard to time points for blood collection, it is not the scope of the literature review to guide you here in my humble opinion, but it should be viceversa. Indeed, a MA can answer some questions regarding points not clear in the review, having a protocol with specific key points (e.g., including studies with blood taken > 24 h, this may have answered to your research question about the chronic effects). I still think that it is not appropriate to include in the same analysis blood taken 12 h post exercise. To avoid the arousal effects, it needs > 24 h, but the authors addressed this in the limitations but please be aware of this important point.
NA
The reviewers have spent significant time evaluating your manuscript and have identified several areas which need to be improved. Importantly, there are several systematic reviews/meta-analyses in this area, it is therefore crucial to differentiate what your manuscript brings to the field. Further, reviewer 1 has highlighted several key queries around the methodology, with particular reference to inclusion criteria. Lastly, reviewer 1 makes a very salient point to include the commercial details/brand for the method of Irisin detection. This is crucial information, given the discordance between numerous studies in terms of methods and kits used to detect Irisin. We look forward to receiving your amended manuscript.
Dear authors,
It is a pleasure to have the opportunity to read your article and review it. The systematic review and meta-analysis investigate the effect of medium- and long-term concurrent aerobic and resistance training on circulating levels of irisin, in overweight or obese individuals. The rationale of the article is the potential beneficial effect that irisin could have on health and metabolic diseases, using physical exercise (i.e., concurrent training) as a non-medical therapeutic tool.
There are currently several systematic reviews and meta-analyses addressing a largely similar research question, so the authors are encouraged to further explain what this revision contributes to the existing evidence (L87-89, L240-242). Specifically, the meta-analysis is similar to the one reported here:
Torabi et al., (2024), https://doi.org/10.4103/ijpvm.ijpvm_76_23, effect of long-term exercise (i.e., any mode of exercise) on circulating irisin in overweight or obese individuals.
Accordingly, the summary of the existing evidence in lines 77 to 81 could be improved by including the most recent meta-analyses on similar research topics, and subsequently, indicating the rationale behind the meta-analysis reported here. The following is a recent meta-analysis on a similar research topic that might be of interest to the authors:
Jandova et al., (2021), https://doi.org/10.3390/healthcare9111438, effect of long-term exercise (i.e., any mode of exercise) on circulating irisin in individuals of all age groups and health conditions.
Other minor comments:
Figures on publication bias and sensitivity analyses could be provided in supplementary material rather than in the manuscript. Conversely, it is more valuable that the results of subgroup analysis (Supplementary Data S2) be presented in the manuscript.
Has it been statistically proven that there is no effect between performing aerobic and resistance training on the same day or alternate days?
L48: typographical error.
L61-65: a more detailed description of irisin, its precursors and its cleavage process would improve this section of the introduction.
L94: the word “meticulously” might be removed.
L129-136: provide the appropriate citation of this tool (https://doi.org/10.1136/bmj.l4898).
L271: update references (e.g., https://doi.org/10.1210/endrev/bnab003)
The table and figures are well presented. However, forest plots should indicate the x-axis legend (favours control/favours experimental). In addition, figure captions should be improved and provide a complete description of the figure content. They also need to be self-descriptive (abbreviations).
Methodologically, the structure of the systematic review and meta-analysis is adequate, although the contents listed below are mandatory to be complete, and will significantly improve the reporting quality.
1. The inclusion criteria are not complete. The measurement tool for the outcome should be specified in the inclusion criteria (e.g., ELISA, WB, HPLC…), including the time points at which it is performed at the pre- and post-intervention (L124).
2. Similarly, the commercial brand and model in the measurement of irisin in the included articles is not reported (Table 1).
3. Heterogeneity assessment might include the Cochrane Q test.
4. There is no method used to assess certainty (or confidence) in the body of evidence for each outcome.
The results indicate that a subgroup analysis was conducted. However, the statistical model and method used for the subgroup analysis is not reported. Likewise, there is no evidence that a test of subgroup differences was executed. In relation to this comment, the reported results seem not to support the conclusion that a shorter period of training (i.e., <10 weeks) is more effective in increasing circulating irisin (L36-39, L219-223, L245-246, L352-354). In addition, a rationale is required to justify why 10 weeks has been used as the cut-off point between groups.
Accordingly, the authors are asked to statistically determine whether there are significant differences between subgroups. If there are differences, please clearly report the results, but if there are no differences, please restructure the conclusions drawn during the study and the related section in the discussion (L272-300).
Finally, the measurement times for irisin after the interventions ranged from 12 to 48 hours after exercise (L199). However, it has been shown that irisin could also be cleaved during recovery period (until +72h) after exercise-induced muscle damage (https://doi.org/10.3389/fphys.2023.1331878). Therefore, the authors are asked to further discuss the possible impact of the measurement time on the circulating irisin results (L264-267).
Dear authors and editors,
I thank you the authors for the job done. The analyses and the manuscript sound good. However, I have raised a major point concerning the time points included in the analyses, which may have biased the results. Please see the comment below.
Line 46: the manuscript may benefit of a better open sentence talking about epidemiology of obesity etc.
Line 53: myokines are sub-type of cytokines, they don’t include cytokines, rather it is vice versa. Please revise.
Line 80: the effects of a single bout of exercise can not be compared to the resting levels of irisin, as systemic levels are influence by different factors whilst acute effects are influenced by exercise only (most likely). Please revise.
Line 82: why endurance training? It is generally referred to aerobic training, as per guidelines.
Line 103: why 2 searches? Why the authors did not use mesh and truncation?
Line 116: S in capital, please revise.
Line 119: any threshold for elderly (e.g., 65 y)?
Line 121: the authors here mention aerobic training, please be consistent with term to help readers.
Line 130: did you use Rob1 or 2? Please specify.
Line 193: please revise ET with AT.
Line 195: can 4 weeks be considered enough to alter irisin? Did the authors consider any minimum threshold for training duration (e.g., > 8 w)? Also, the manuscript may benefit of detailed training mode order. AT and RT were performed in the same session? Which one goes first? How many RT and AT per week? Please expand.
Line 199: what was the time frame to include study in terms of blood collection? It is known that blood immediately after compared to 24-48 h after the last training session really impact cytokines and myokines. Did the author consider that? Blood after 12 h (as a minimum threshold) can still have the arousal effects of exercise, how did you deal with this? This is a major point.
Line 241: if authors aim was to investigate chronic effects of exercise, then including blood collection 12-h after the last training session can not properly answer to that research question. As at 12-h the arousal effects are still in the human body, and this can not be considered a chronic effect of exercise. As you correctly mention in line 267, the systemic levels of irisin 24/48 h after can be attributed to the systemic changes induced by exercise, whilst this is not for the 12-h time point (arousal effect).
Line 294: I would remove this sentence, as it appears in contrast with the sentence below.
Line 328: the authors should be aware that these are the arousal effects of exercise and can not be the same for chronic training.
Time points should be revised, please see above.
no comment
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