Study protocol High-intensity interval training and cardiorespiratory fitness: an overview of systematic reviews and meta-analysis Helal L, Botton CE, De Nardi AT, Page MJ, Domingues MR, Umpierre D 21 January 2018 Authors Lucas Helal, MSc Hospital de Clínicas de Porto Alegre, Graduate Program on Cardiology and Cardiovascular Sciences, Federal University of Rio Grande do Sul. Cintia Ehlers Botton, PhD Hospital de Clínicas de Porto Alegre, Health Technology Assessment Institute, Federal University of Rio Grande do Sul. Angelica Trevisan De Nardi, MSc Hospital de Clinicas de Porto Alegre, Graduate Program on Cardiology and Cardiovascular Sciences, Federal University of Rio Grande do Sul. Matthew J Page, PhD School of Public Health and Preventive Medicine, Monash University, Australia Marlos Rodrigues Domingues, PhD Kinesiology School, Federal University of Pelotas *Daniel Umpierre, PhD Hospital de Clínicas de Porto Alegre, Graduate Program on Cardiology and Cardiovascular Sciences, Federal University of Rio Grande do Sul.
[email protected] *corresponding author and guarantor of the review Registry This overview systematic review is registered at the PROSPERO database (CRD42017067269). Funding and role of the sponsor This study has no funding source. Disclosures Daniel Umpierre receives research productivity grant and support from the CNPq foundation. Cintia Botton receives post-doctoral fellowship funding support from the IATS foundation. Lucas Helal and Angelica De Nardi receives doctoral funding support from the CAPES foundation. Matthew J Page is supported by an Australian National Health and Medical Research Council (NHMRC) Early Career Fellowship (1088535). The authors don’t have any personal, religious, cultural or business potential conflict of interests to declare, as well as no personal/working relationship with any to the authors that will have their SRMA’s addressed in this work.
Background and rationale Systematic reviews and meta-analysis (SRMA) may provide high-quality evidence synthesis and guide decision-making processes in different study fields (1). Together with the rise in studies with primary data, SRMA have also been increasingly published over time (2). Although SRMA’s are routinely considered reliable and methodologically robust, evidence indicates lack of transparency and high-methodological standards on this type of study among the biomedical literature (3). Regarding physical exercise research, interventions consisting of high-intensity interval training (HIIT) have received considerable academic interest, which is visible by the increasing number of publications, both as primary studies and, more recently, as SRMA's. In clinical and nonclinical populations, there are efforts aiming to assess HIIT efficacy on several outcomes. However, manifold primary studies rely on small samples and non-randomized or partially controlled interventions (e.g., without active comparators such as moderate intensity continuous training – MICT), which may favor equivocal results (4,5,6). These heterogeneous methods are ultimately reflected in SRMA's and may increase the uncertainty of summary estimates (7,8). Besides, there are many SRMA's that lack comparator groups and, therefore, reduce the potential to assess the efficacy of HIIT compared to other forms of exercise, especially in cardiorespiratory fitness which is the most likely affected outcome by manipulation of exercise training intensity (9,10). Therefore, based on the high volume of SRMA's addressing HIIT efficacy in increasing VO max in a very short timeframe; the discrepancies on effect sizes of SRMA's; and the potential low methodological quality, we designed an overview of SRMA's addressing HIIT effect on VO max regardless of population to summarize the available evidence, as well as to summarize methodological quality of SRMA's and to explore potential sources of divergence, regarding quality of reporting and methods. 2
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Objectives Our first aim is to summarize the available evidence on completed SRMA's by a qualitative approach. Our secondary aims are: a) to comprehensively characterize the nature, quality of reporting and methods of these SRMA's; b) to compare SRMA’s adherence to quality of reporting and methods stratified by some publication characteristics (e.g. Journal of Citation Reports - JCR Impact Factor or the self-report as PRISMA-based).
Methods This overview of systematic reviews is registered (CRD42017067269) (11). All the methods will be guided by the Cochrane Collaboration recommendations (12) and the reporting reported according to the Preferred Reporting Items to Systematic Reviews and Meta-Analysis (PRISMA) Statement (13). The overview’s design will attempt to identify all available SRMA's addressing HIIT effect on VO max. This protocol was written in accordance with the PRISMA-P statement (14). 2
Eligibility criteria To be eligible for inclusion, articles need to be systematic reviews and meta-analysis of highintensity interval training or sprint interval training (SIT) addressing VO max as one of the outcomes. No restriction to population (clinical and non-clinical population), publication status (published and unpublished data) or publication language will be used. Meta-analysis of VO max does not have to be presented in graphical format (i.e., forest plot) and does not need to be the primary outcome of the SRMA. We used the definition of HIIT and SIT by MacInnis and Gibala 2016 (15) - HIIT defined as interval-based programs on near maximal intensity (85-95% of maximal heart rate – HR); and SIT defined as interval-based programs at maximal intensity (above 100% of VO max or all-out intensity). 2
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Searching To comprehensive survey the literature, we will search five electronic databases for indexed full-texts (PubMed, MEDLINE®, EMBASE, Cochrane Database and SciELO), one database for grey-literature (Google Scholar) and one database for registries (PROSPERO) from the earliest available date to November 2017. The SRMA's and relevant paper references will be checked manually. The full-search strategies are presented in Appendix 1. Eligibility If fewer than 150 titles and abstracts are retrieved, the entire eligibility phase will be performed by checking the full-text. If more than 150 titles and abstracts are retrieved, the first phase of eligibility will be done by checking manually titles and abstracts in standardized spreadsheets and then we will proceed for full-text eligibility assessment. The process will be performed by two independent reviewers (LH and MD), marking all eligible and ineligible records with reasons (all fulltext checking process) or marking all potential eligible and ineligible records with reasons (by titles and abstracts first). Any discordance will be solved by personal agreement and, in case of discordances, a third reviewer opinion (CB or DU) will be requested. Authors can be contacted to provide further information in case of incomplete data. The list of included and excluded studies (with reasons) will be provided and will be presented by a PRISMA flow-diagram and in the full text-body as well. Data extraction Data from all the eligible SRMA's will be extracted and the process will be conducted by two independent reviewers (LH and CB) on a spreadsheet. The data extractors will independently pilottest the form using five included papers to ensure consistency in interpretation of data items, or to assume internal definitions and improvements of the forms questions. Subsequently, data from each
SRMA will be independently extracted by each reviewer. Any discrepancies in the data extracted will be resolved via discussion or adjudication by a third reviewer if necessary. As the outputs of the forms will be firstly addressed as text data, a third researcher, not involved in the extraction process, will recode the information into pre-coded numbered variables (e.g., 0 for NO and 1 for YES) for the analysis. The double check will be done on the level of raw information. The extracted items will be divided into: a) summary evidence; b) epidemiological characteristics; c) quality of reporting; d) quality of methods; e) results. For the summary evidence, information regarding population, intervention, comparator, outcome, settings, effect size (with precision estimators) will be extracted. As for epidemiological description, characteristics such as number of authors, country of correspondence author, year of publication, journal’s impact factor, journal type, studied population, number of included studies, sample size, register, funding, disclosures etc. will be extracted based on items included in Page et al 2016 (4). For quality of reporting, core items of the PRISMA checklist will be extracted and, for methodology, the extracted items will be based on the Cochrane Standards for Systematic Reviews and Meta-Analysis (Cochrane Handbook), the AMSTAR-1 tool and other sources of well-recognized methodological aspects for SRMA’s. For the results, summary effect sizes with estimators will be extracted, as well as heterogeneity statistics. Risk of bias The risk of bias (RoB) in SRMA's will be assessed by the AMSTAR 1 tool (16) by two independent reviewers (LH and CB). Any discrepancies in the data extracted will be resolved via discussion or adjudication by a third reviewer if necessary. We decided to rate the study's RoB by the AMSTAR 1 to avoid some unfair judgment, since the new one (AMSTAR-2) (17) was published just in 2017. Analysis plan The first step of our analysis is to present a comprehensive summary table with qualitative data from all available SRMA's as follows: a) reference number (hyperlinked to the reference list if possible); b) authors; c) journal title; d) year of publication; e) population studied in detail; f) brief details of the intervention; g) brief details of the comparator (if present); h) outcome with directions and statistics ; j) settings (study design with details); k) the presence of funding for the study conduction; l) the authors’ disclosure reported. As for the second step, we intend to present quantitatively the effect sizes for VO max, with estimators, for each SRMA. In the case of differences regarding the chosen summary measure (WMD, SMD, Cohen’s d, Hedges’ g), we will present data grouped by summary measure. If more than one meta-analysis for VO max was performed by the authors (e.g., subgroup, sensitivity), we will consider presenting their effect sizes as well. Whenever possible, we will present it graphically. The third step of our analysis is still consisted by a quali-quantitative approach, where tables with descriptive statistics will be presented regarding information of epidemiology, quality of reporting and methods of included SRMA's for the all available SRMA's and stratified by population (clinical and non-clinical). Following the analysis, our fourth step will be to generate the frequencies of adherence to AMSTAR 1 items and study's overall score. 2
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Finally, we will compare the frequencies of adherence to quality of reporting and methods items (expanded to the aforementioned ones) between studies, stratifying them by self-reported use of the PRISMA Statement, by journal impact factor and by health population status.
Statistical analysis All analyses will be performed using Stata version 14 and R version 3.4.1 software’s. The descriptive analysis will be presented by absolute or relative frequencies for categorical variables, and by central tendency measure ± dispersion measure (i.e., mean ± standard deviation or median ± interquartile range). Associations between studies adherence to quality of reporting and methodological items and the exposures characteristics will be presented as risk ratios ± 95%CI. Significance level will be set at 0.05 for all statistical inferences. Continuous potential exposures, like journal impact factor, will be dichotomized according to the overall median. Categorical potential exposures, such PRISMA self-referring, will be preserved by its nature. The outcomes will be dichotomized by YES or NO regarding its adherence (e.g., the presence of the terms "systematic review" and/or "meta-analysis" on the title). Subgroup Analyses To explore associations on adherence of quality of reporting and methods items, we will run subgroup analysis apportioning studies by: -
Self-reported as PRISMA-based vs non-self-reported as PRISMA-based SRMA; Clinical vs. non-clinical population SRMA’s; JCR (Impact Factor by Journal of Citation Reports) dichotomized by the overall median. We will consider the JCR of the publication moment.
Sensitivity Analyses Sensitivity analysis for predictors of adherence can be performed depending on the risk of bias analysis.
Outcome Definitions We consider it appropriate to explain the main definitions that reviewers will use to determine whether evaluated studies will address or not the following items. The first rule assigned was how the information provided allows study replication. Secondly, after eight years of the first PRISMA publication and spreading among scientific literature, we will also be rigorous whether the information is explicit for readers - i.e., it should be clear to readers what authors did or intended to do. Below, we describe what we will consider for each evaluated item that has no established definition (e.g., AMSTAR or PRISMA-based item). 1. Is the journal a general or specialty journal? As for General journal, we will consider those with the scope of the entire biomedical literature: Journal of the American Medical Association (JAMA), British Medical Journal (BMJ), Annals of Internal Medicine, New England Journal of Medicine (NEJM) and The Lancet. Any other journal will be considered as of Speciality. 2. Which of the following terms are in the title or abstract of the review? (Systematic review, meta-analysis, or both). We will perform a simple check of the title and abstract of the full-text. 3. Is there a clear definition of the intervention? For clear definition of the intervention, we will support our decisions on the FITT principle for exercise interventions - F for frequency, clear stated as daily, weekly or monthly; I for intensity, where authors should clearly state the intensity range individuals need to exercise and how it was measured; T for time, which reflects mostly the volume of training session; and T for type, where authors should be clear about the kind of modality (or ergometer) utilized. 4. Is this a HIIT or SIT (or both) as primary intervention? For HIIT and SIT we will consider the aforementioned definitions on the Eligibility Criteria section. We will check the table and reference list in order to classify it. For this topic, we will not consider only the authors’ statement. 5. Is there a clear definition of the studied population? The studied population should be classified regarding their health status, athletic status (in case of athletes) and age. If more than one population was studied, authors should state clearly all of them. A more unspecified statement like "cardiometabolic conditions such as..." will not be rated as clear.
6. What is the source of funding of the SR? This item is about reporting the funding presence or not for the study (and not for author's personal funding). In the case of presence, funding source will be divided into profit and nonprofit institutions. 7. Did the authors report registering this review? Statement of registering the study in one of the available platforms will be considered (e.g., PROSPERO). We will evaluate studies adherence to registration for those published from 2012 and after (PROSPERO starting year: 2011).
8. Did the authors report working from a protocol or a priori established methods? Statement of working in a protocol a priori will be checked, and authors should clearly indicate where the protocol can be found. We will accept protocols published in indexed journals or open source platforms (e.g., Open Science Framework) 9. Which reporting guideline (if any) did the authors report using to guide reporting of the review? The self-referring in accordance with a reporting guideline (e.g., PRISMA) will be checked. The solely use of a PRISMA flow diagram will be not considered as following PRISMA guidelines. 10. Reported study hypothesis? We will check if authors stated clearly their study hypothesis before methods. 11. Reported primary outcome/meta-analysis? We will check if authors stated clearly their study primary outcome in the case of more than one outcome evaluated. Further analysis topics related to primary outcomes will be considered independently of VO max, in order to preserve author's internal definitions and avoid any penalization. If just only one outcome was assessed, the "does not apply" term will be used for options related to multiple outcomes. 2
12. Was VO max the primary outcome? 2
In the case of more than one outcome in the meta-analysis, we will check if VO2max was stated as the primary one. 13. Did the authors report using Cochrane review methods? We will evaluate if authors refer the Cochrane Review methods on the Methods Section as a guidance for the conduction of the review, even for non-Cochrane reviews. We will accept the only selfreferring. The use of the Cochrane Tool for risk of bias assessment will not be considered as guided by Cochrane Methods.
14. Did the authors make a statement regarding eligibility of studies based on their publication status? By publication status, we will consider whether authors declared that they included just published research (i.e., scientific journals) or if they considered an inclusion of industry reports, thesis and dissertation and then. Authors should clearly state they intended to include or not unpublished data. For example, the only mention of thesis/dissertation hand-searching will not be considered enough. This question is not about if they included or not but if they did declare something about it. 15. Did the authors make a statement regarding eligibility of studies based on language of publication? Authors should clearly state if they considered or not to include studies due to its language. The only limit term on the search strategy will not be considered. 16. What languages were reported as being eligible for inclusion in this review? If authors made a statement regarding the language for eligibility criteria, we will describe what languages were considered for inclusion (English, Spanish or all languages). 17. Did the authors make a statement regarding eligibility of studies based on study design? We will check if authors restricted their eligibility for study design (e.g., randomization, control or placebo status). Authors should clearly state their prior intentions. The checking of reference list will not be acceptable for this question. 18. Which study designs were eligible for inclusion in the review? For this topic, we will perform a hand-search to check what kind of study designs were included. 19. How many electronic bibliographic databases were searched? We will manually check on the Methods section the bibliographic databases. Register and grey literature databases do not account here. 20. Were the years of coverage reported for electronic bibliographic databases? For this question, we will consider as full coverage (start date and end date of published study year); partial coverage (when authors stated they searched until a given year); and unclear in the case of no statement. If authors state that they will include studies from the first available date until a given year or with no restriction date, we will give a full coverage check. 21. Were search terms reported for one or more of the electronic databases? We will check if authors reported or indicated for a supplementary file the search strategy. We will consider search strategy by full boolean strategy, only MeSH terms or only free-text. By full boolean strategy, the presence of OR, AND or NOT operators are needed. For MeSH terms, they should be
clear stated as one of them, otherwise, it will be considered as a free-term. We will not check if a free term could be considered as MeSH. The full text strategy could be referred to be available in the registry, protocol or any other a priori document as well. 22. Did the authors report searching at least one study registry to identify ongoing or completed studies? We will check if authors perform a search on a registry database such as www.clinicaltrials.gov. 23. What method of risk of bias (or quality) assessment did the authors report using? We will check if authors intended to measure the risk of bias of primary studies (we will consider the heading Methodological Quality as similar) and the tool as well. 24. Did the authors report whether or not they contacted (or attempted to contact) corresponding authors of included studies for any unpublished data? For this topic, authors should clearly state whether they contacted study authors for complementary data after the search strategy process. 25. Was the review flow (i.e. a description of the number of records screened and included/excluded) reported in the review? For the review flow, we will consider as presented on a flow-diagram or in the text. 26. Were the reasons for the exclusion of studies from the systematic review reported? The reasons should be clearly stated. If only the number of excluded studies are mentioned, the decision will be of insufficient reporting. 27. What was the total number of records retrieved across all searches (electronic or not)? This item refers to this first step of the eligibility and inclusion process- i.e., how many citations were retrieved by all electronic databases. 28. What was the number of titles/abstracts screened after duplicate references were removed? This item refers to the second step of the eligibility and inclusion process - i.e., how many citations were present after the exclusion of database duplicates to be considered for full-text checking. 29. What was the number of full-text articles sought for more detailed evaluation by reviewers? This item refers to the third step of the eligibility and inclusion process - i.e., how many full-texts were checked for eligibility.
30. What was the number of studies included in the systematic review and meta-analysis? This item refers to the final number of studies included for the quantitative synthesis, independently of the outcome. 31. Are the included studies cited/listed, as text or table? We will check if authors presented their included studies in a table or in the text with references. 32. Is there a comprehensive summary table of included study (characteristics, intervention, outcome, direction of results)? By comprehensive summary table, we will adopt the Cochrane Collaboration recommendations, which means that the table needs to present: a) the studied population; b) the interventions (active and comparator, in case of controlled trials); c) and the outcome with the results and its directions. The results and directions of the outcome will be mandatory for this item. 33. Did the authors report including grey literature in the systematic review? Authors should clearly state if they checked or not any source of grey literature by any means. By grey literature, we considered conference abstracts, internal reports, health technology assessments or any other source as in accordance with the Cochrane Collaboration recommendations. 34. What was the total number of participants in the study? This item refers to the total number of participants in the study. Authors should clearly present the total amount. 35. Was the total number of participants presented in the abstract? We will check if the total number of participants is stated in the abstract. 36. Are the total number of participants in the study the same on abstract and full-text? We will check, in the case of participants total amount presence, if the number is the same as in the abstract. 37. Are the number of per meta-analysis participants presented in the full-text? For this item, the graphical view could be considered or by the text. If at least one meta-analysis will be presented without the number analyzed, this item will be rated as insufficient.
38. Did the review authors specify in the Methods section the outcomes that were eligible for inclusion in the review? Authors should clearly state what outcomes they are considering for analyses. Embracing terms were not considered. Example: "body composition". Correct: "body mass index, or waist circumference, waist-to-hip ratio etc.". 39. How many outcomes were specified in the METHODS section? We will manually retrieve the number of outcomes specified on the methods considering the classification above. 40. How many outcomes were presented in the RESULTS section? We will check if the authors presented the outcomes summary measures they stated before. 41. What type of outcome is the (1st) primary outcome? We will consider for this question the nature of the variable: continuous, dichotomous, etc. In cases where authors did not specify a primary outcome, we will consider the first (index) meta-analysis. If only one outcome was analyzed, this classification will be used. 42. What is the unit of measure of the first reported result (effect estimate) of the primary outcome? We will consider how authors opted to present their summary effect estimate - weighted mean differences, standardized mean differences etc. In the cases when authors did not specify a primary outcome, we will consider the index meta-analysis. If only one outcome was analyzed, this classification will be used. 43. What is the statistical significance of the first reported result (effect estimate) of the primary outcome? We will consider the directions (favors/disfavors) and the statistical significance of the results. In cases when authors did not specify a primary outcome, we will consider the index meta-analysis. If only one outcome was analyzed, this classification will be used.
44. What is the unit of measure of the VO max meta-analysis? 2
We will consider how authors chose the summary effect estimate - weighted mean differences, standardized mean differences etc. for the VO max meta-analysis. If two or more analyses were performed, we will evaluate the overall meta-analysis, or, in the absence of an overall effect, the first presented (index meta-analysis). 2
45. What is the statistical significance of the VO max meta-analysis? 2
We will consider the directions (favors/disfavors) and the statistical significance of the result for the VO max meta-analysis. If additional analyses (subgroup, sensitivity or meta-regression) were generated, we will evaluate the overall meta-analysis, or, in the absence of an overall effect, the first presented (index meta-analysis). 2
46. Which meta-analysis model was used in the meta-analyses? We will consider the meta-analysis model as fixed or random effects. This question refers to the definitions presented on the item 41. 47. Which meta-analysis model was used for VO max meta-analysis? 2
We will consider the meta-analysis model as fixed or random effects. If more than one analyses (subgroup, sensitivity or meta-regression) were performed, we will evaluate the overall meta-analysis, or, in the absence of an overall effect, the first presented (index meta-analysis). 48. Was any method described to formally evaluate statistical heterogeneity of included studies? We will consider whether authors formally tested heterogeneity by a statistical approach. This question refers to the definitions presented on the item 41. 49. Was there any method described to formally evaluate statistical heterogeneity of included studies on VO max meta-analysis? 2
We will consider whether authors formally tested heterogeneity by a statistical approach for VO max assessment. If more than one analyses (subgroup, sensitivity or meta-regression) were performed, we will evaluate the overall meta-analysis, or, in the absence of an overall effect, the first presented (index meta-analysis). 2
50. Did the authors report that a measure of statistical heterogeneity (e.g. χ , I ) or any other) was used to justify use of a fixed-effect or random-effects meta-analysis model)? 2
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We will consider if the authors justified the meta-analysis model by its overall heterogeneity. 51. Did the authors report assessing (or an intent to assess) publication bias? We will consider if the authors stated an assessment (or an intention) of asymmetry or publication bias. If studies for VO max assessment differs from the overall included, we will check this question specific to that for VO max assessment. 2
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52. Did the authors discuss the results in relation to potential publication bias? We will judge if the authors mentioned any potential influence of publication bias (or its absence) on their results. 53. Which of the following additional analyses did the authors conduct? We will check if the authors ran subgroup, sensitivity or meta-regression analyses. We will check it for the overall outcomes and specifically for VO max. 2
54. Was the sensitivity analysis pre-specified on the methods? If this analysis was conducted, we will check if authors pre-specified this additional analysis on the Methods. 55. Was the meta-regression analysis pre-specified on the methods? If this analysis was conducted, we will check if authors pre-specified this additional analysis on the Methods. 56. Did the authors report an assessment of the quality of evidence using the GRADE approach? We will check if authors considered to rate the evidence across studies by GRADE approach. 57. Were there any limitations reported in the Discussion section? We will check if authors pointed out any limitation on the discussion section. We will consider and divide limitations into a) study-level, such as differences in exercise protocol, VO max assessment etc.; b) meta-analysis-level, such as the presence of studies with high risk of bias, heterogeneity, publication bias etc. or c) both. 2
58. Was the risk of bias/quality/limitations of the included studies incorporated into the abstract conclusion? If authors performed risk of bias or methodological quality assessment, we will consider if they mentioned their results on the abstract.
59. Did the authors make adequate conclusions based on the findings, on pre-specified objectives? We will consider whether authors’ conclusion adhered to pre-specified objectives. In the case of objectives not previously specified, we will read the paper and consider a reasonable decision about it.
60. Are the conclusions of the full-paper in accordance with that stated on the abstract? We will check if the conclusions in the text and abstract are in accordance. It does not mean they need to be ipsis litteris copied. A reasonable judgment will be performed here as well. 61. Did review authors declare whether they had any conflicts of interest? This topic regards whether authors report their potential (or its absence) conflicts of interest.
AMSTAR criteria We found appropriate to explain the criteria that reviewers will use to application of AMSTAR. The criteria are own definitions of AMSTAR for each question. 1)
Was an “a priori” design provided?
We will rate YES if there is a statement of an a priori protocol published or registered, (e.g., PROSPERO, Open Science Framework). 2)
Was there duplicate study selection and data extraction?
We will rate YES if have a statement referring that there were at least two independent reviewers selected potential eligible studies AND extracted data, and if the authors described a consensus procedure for possible disagreements. If just one of them (i.e., study selection or data extraction) was performed in duplicate, it will be rated as NO. 3)
Was a comprehensive literature search performed?
We will consider YES if at least two electronic sources (e.g., PUBMED and EMBASE) PLUS one supplementary strategy searching (e.g., a grey literature search counts as supplementary, like Google Scholar, dissertations, Conference Annals etc), AND the reporting of include years and databases used. Key words and/or MESH terms must be stated, and where feasible, the search strategy should be provided. All searches should be supplemented by consulting current contents, reviews, textbooks, specialized registers, or experts in the particular field of study, and by reviewing the references in the studies found. 4)
Was the status of publication used as an inclusion criterion?
We will consider YES when authors stated clearly whether or not they excluded reports based on the status of publication regarding access (published and unpublished) or language or study quality. For published literature, we will consider those available on indexed journals. Unpublished literature could be considered as internal reports, dissertations, registry databases etc. Due to AMSTAR’s original rating scale (just YES or NO), in the case of an absence of statement, we will rate as NO, to avoid unfair penalization. 5)
Was a list of studies (included and excluded) provided?
We will consider YES when a list of included AND excluded studies to be provided as table/list /figure or supplementary material. The inclusion of included and excluded studies in the reference list is not sufficient. 6)
Were the characteristics of the included studies provided?
We will consider YES if there are sufficient characteristics data (e.g., age, race, sex, relevant socioeconomic data, disease status, duration, severity, participants, interventions/exposure AND
outcomes) from the original studies as aggregated form such as a table to describe the included studies. We will consider the presence of the outcome as mandatory for YES. Several studies on physical exercise report a table, but limit it to the intervention characteristic. 7)
Was the scientific quality of the included studies assessed and documented?
We will consider YES if authors evaluated the quality of primary studies (or "risk of bias", as usual). It can be done by a standardized quality scoring tool or checklist (e.g., Cochrane Tool, PEDro Scale, etc) or an unstandardized tool (created by the authors). 8)
Was the scientific quality of the included studies used appropriately in formulating conclusions?
We will rate as YES if the authors refer that the methodological rigor and scientific quality, previous evaluated, was discussed in the analysis and/or conclusions of the review. We will not consider YES for this question if we scored NO for question 7. In this case it will be rated as NOT APPLICABLE. 9)
Were the methods used to combine the findings of studies appropriate?
We will consider YES if: -
The ensure of study’s combination (assessment of homogeneity); In the presence of heterogeneity (I > 50%), the use of random effects; The use of a standardized summary effect in the case of differences in primary data unit measure; 2
10) Was the likelihood of publication bias assessed? We will rate YES if an assessment of publication bias was intended (graphical aids - e.g., funnel plot) and/or statistical tests (e.g., Begg and Egger’s test). The absence of test values or funnel plot will be rated as NO. If authors mention that publication bias could not be assessed because there were fewer than 10 included studies we will score as YES. 11) Was the conflict of interest included? We will consider YES if potential sources of support are clearly acknowledged in both the systematic review AND primary included studies. Definitions made during the review (to this time) a) If one eligible systematic review states a primary outcome which is not VO max, analysis for primary outcomes will be performed to that was stated by the authors; b) In cases when authors do not state the SRMA primary outcome, VO max will be considered as the primary outcome; c) VO max not necessarily needs to be directly assessed by maximal test (e.g., indirect assessment as by heart rate and submaximal estimation will be considered valid). 2
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Strength of the evidence Not applicable as no overall quantitative summary measure is planned for the overview synthesis phase. Data Sharing Plan This overview systematic review is underpinned on some practices of research transparency and reproducibility. To this, a data-sharing policy is planned as follows: -
The list of included/excluded studies will be publicly available immediately after the eligibility process finalization; The data extraction spreadsheet will be publicly available after the publication of the main results. No coding will be performed at the study level; The extraction forms will be publicly available after the releasing of the study protocol; The study glossary and internal definitions will be provided after the publication of the main results.
All data will be made available in Open Science Framework, GitHub and Research Gate platforms.
References
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Appendix 1
Search strategy The search strategies were tested previously with and without descriptors (e.g., [tiab], [mesh], [ti]) and the one that returned the maximal titles and abstracts values was chosen. PubMed #1 (high intensity interval training OR high intensity interval exercise OR HIIT OR HIIE OR aerobic interval training OR sprint exercise OR sprint interval training OR sprint interval exercise OR SIT) #2 (cardiorespiratory fitness OR maximal oxygen uptake OR aerobic fitness OR aerobic capacity OR VO2max OR VO2peak) #3 ((Medline[tiab] OR (systematic[tiab] AND review[tiab]) OR meta-analysis[ptyp]) #1 AND #2 AND #3 EMBASE #1 (‘high intensity interval training’/exp OR ‘high intensity interval exercise’/exp OR high intensity interval training OR high intensity interval exercise OR HIIT OR HIIE OR aerobic interval training OR ‘aerobic interval training’/exp OR ‘sprint exercise’/exp OR sprint exercise OR sprint interval training OR ‘sprint interval training’/exp OR sprint interval exercise OR ‘sprint interval exercise’/exp OR SIT) #2 (‘cardiorespiratory fitness’/exp OR maximal oxygen uptake OR aerobic fitness OR aerobic capacity OR VO2max OR VO2peak) #3 ((systematic AND review) OR meta-analysis) #1 AND #2 AND #3 Cochrane Library → no filter need (directly to SRMA - Cochrane Systematic Review Database) #1 (high intensity interval training OR high intensity interval exercise OR HIIT OR HIIE OR aerobic interval training OR sprint exercise OR sprint interval training OR sprint interval exercise OR SIT) #2 (cardiorespiratory fitness OR maximal oxygen uptake OR aerobic fitness OR aerobic capacity OR VO2max OR VO2peak)
Scielo Search #1: #1 (high intensity interval training OR high intensity interval exercise OR HIIT OR HIIE OR aerobic interval training OR sprint exercise OR sprint interval training OR sprint interval exercise OR SIT) #2 (cardiorespiratory fitness OR maximal oxygen uptake OR aerobic fitness OR aerobic capacity OR VO2max OR VO2peak) #3 ((systematic AND review) OR meta-analysis) #1 AND #2 AND #3 Search #2: #1 (treinamento intervalado de alta intensidade OR exercício intervalado de alta intensidade OR HIIT OR HIIE OR treinamento intervalado aeróbico OR exercício de sprints OR treinamento intervalado de sprints OR SIT) #2 (aptidão cardiorrespiratória OR consumo máximo de oxigênio OR aptidão aeróbica OR capacidade aeróbica OR VO2max OR VO2peak) #3 ((sistemática AND revisão) OR meta-análise) #1 AND #2 AND #3
