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Systematic Review
DOI: 10.1016/j.bjpt.2020.04.007
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Available online 19 May 2020
Investigating the rigour of research findings in experimental studies assessing the effects of breaking up prolonged sitting – extended scoping review
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Coralie Englisha,b,
Corresponding author
coralie.english@newcastle.edu.au

Corresponding author at: School of Health Sciences, The University of Newcastle, Australia.
, Ishanka Weerasekaraa,c, Anjelica Carlosa,d, Sebastien Chastine,f, Gary Crowfoota,g, Claire Fitzsimonsh, Anne Forsteri, Elizabeth Hollidayj, Heidi Janssena,d,g, Paul Mackiea,g, Gillian Meadk, David Dunstanl,m
a School of Health Sciences and Priority Research Centre for Stroke and Brain Injury, The University of Newcastle, Newcastle, Australia
b Centre for Research Excellence in Stroke Recovery and Rehabilitation, Florey Institute of Neuroscience and Hunter Medical Research Institute, Newcastle, Australia
c Department of Physiotherapy, Faculty of Allied Health Sciences, University of Peradeniya, Peradeniya, Sri Lanka
d Hunter Stroke Service, Hunter New England Local Health District, Newcastle, Australia
e Department of Movement and Sport Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
f School of Health and Life Science, Institute of Applied Health Research, Glasgow Caledonian University, Glasgow, UK
g Centre for Research Excellence in Stroke Recovery and Rehabilitation, Florey Institute of Neuroscience, Melbourne, Australia
h Physical Activity for Health Research Centre, Institute of Sport, Physical Education and Health Sciences, University of Edinburgh, Edinburgh, Scotland, UK
i Academic Unit of Elderly Care and Rehabilitation, University of Leeds, Bradford, UK
j School of Medicine and Public Health, The University of Newcastle, Newcastle, Australia
k Geriatric Medicine, Division of Health Sciences, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
l Physical Activity Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia
m Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia
Highlights

  • Only 50% of the published trials were registered.

  • Unregistered trials may have collected other measures that remain unreported.

  • Many additional outcomes not appearing in trial registries were published.

  • Some reported positive findings are likely spurious due to unadjusted multiple comparisons.

Received 13 September 2019. Accepted 30 April 2020
Article information
Abstract
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Table 1. Summary of trials and outcomes.
Abstract
Objectives

Sedentary behaviour research is a relatively new field, much of which has emerged since the widespread acceptance of clinical trial registration. The aim of this study was to investigate the trial registration and related issues in studies investigating the effect of frequent activity interruptions to prolonged sitting-time.

Methods

Secondary analysis of a scoping review including systematic searches of databases and trial registries. We included experimental studies investigating the effects of frequent activity interruptions to prolonged sitting-time.

Results

We identified 32 trials published in 45 papers. Only 16 (50%) trials were registered, with all 16 trials being completed and published. Of the unregistered trials, we identified three (19%) for which similarities in the sample size and participant demographics across papers was suggestive of duplicate publication. Identification of potential duplicate publications was difficult for the remaining 13 (81%). Results from 53 (76%) of the 70 registered outcomes were published, but 11 (69%) registered trials reported results from additional outcomes not prospectively registered. A total of 46 different outcomes (out of 53 reported outcome measures, similar measures were collated) were reported across all trials, 31 (67%) of which were collected in ≤2 trials.

Conclusions

We found direct evidence of trial registration issues in experimental trials of breaking up sitting-time. The lack of prospective registration of all trials, and the large number of outcomes measured per trial are key considerations for future research in this field. These issues are unlikely to be confined to the field of sedentary behaviour research.

Keywords:
Sitting-time
Sedentary behaviour
Publication bias
Physical activity
Full Text
Introduction

Sedentary behaviour is an emerging field of research, and as with all emerging fields there has been much excitement about early findings. As the field grows, it is important that it is closely scrutinised for potential issues of bias. Systematic reviews and meta-analyses are ways of synthesising published research literature. However, issues such as the non-publication of negative findings (publication bias, the publication of some outcomes and not others (selective reporting)), the reporting of same outcomes multiple times, and the clarity of outcomes reported in separate papers arising from the same study (duplicate publication bias), affect the trustworthiness of the original publications making reviews more challenging and therefore review findings1 and can lead to the overestimation of effects.2

In an emerging research field, it is also common to see a large number of outcomes being assessed in each trial as new mechanisms of action are hypothesised and exploratory outcomes considered. However, as the number of outcomes assessed per individual participant increases, so too does the risk of Type I error – that is finding statistically significant results that are spurious.3 Clinical trial registries are designed to guard against some of these issues, and most ethics committees, research governance bodies, and medical journals now require all clinical trials to be prospectively registered prior to participant recruitment. While the Cochrane Collaboration requires all reviews to consider issues of publication bias and selective reporting by comparing published findings with trial registry records, this is not widespread across all published systematic reviews, including those in sedentary behaviour research.4

In the world of exercise physiology research, there are two broad fields; physical activity research, focused on the moderate to vigorous end of the exercise intensity spectrum and sedentary behaviour research, focused on the effects of prolonged sitting. While the former is a well-established field with a long history of publication, the latter is in its relative infancy. Much of the physical activity research pre-dates the requirement to register clinical trials. However, the newer field of sedentary behaviour research, especially the literature investigating sedentary behaviour interruption with short bouts of physical activity, provides a unique opportunity to carefully examine how information found in publications are consistent with trial registration information, so as to determine the rigour of reporting of published work.

In this paper, to maintain a reasonably narrow scope, we chose to assess biases by focusing on experimental trials investigating the effect of interrupting prolonged periods of sitting time with frequent, short bouts, of physical activity or standing. In the past five years, this field of research has rapidly expanded with an increasing number of primary trials and systematic reviews being published each year. This is important, given the increasing use of these findings to inform intervention and guideline development.

Therefore, the aim of this study was to examine issues in trial registration, which may suggest publication bias, selective reporting, and risk of Type I error in studies investigating the effect of frequent activity interruptions to prolonged sitting. The specific research questions were in experimental trials investigating the effect of interrupting prolonged periods of sitting time with frequent, short bouts, of physical activity or standing;

  • 1.

    How many published trials have been registered, and of those registered, have all completed trials been published?

  • 2.

    Are duplicate publications from the same trial easily identifiable?

  • 3.

    Are all outcomes recorded in trial registries published?

  • 4.

    How many different outcomes have been measured in each trial?

MethodsIdentification and selection of studies

This paper is an extension of a scoping review5 with systematic searches that aimed to review the evidence for the effect of interrupting prolonged sitting with frequent bouts of physical activity or standing on first or recurrent stroke risk factors. During the initial scoping review, standard guidelines were followed such as independent title and abstract, and full text screening, with discrepancies resolved by a third member of the research team.5 Five databases including Medline, Embase, Allied and Complementary Medicine, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and the Cochrane Library were searched from the inception to February 2018 (full search strategy and methodology previously published5). Experimental trials with adult participants (age ≥18 years), investigating the effect of interrupting prolonged periods of sitting time compared with supervised interventions of frequent, short bouts, of physical activity or standing published in English were included in the review. Only studies that included a control condition of uninterrupted prolonged sitting were included. While the scoping review included only studies that reported at least one outcome measure related to stroke risk factors, in this study we did not exclude studies based on outcome measures.

Identification of trial registration

We used a two-staged approach to search for registered trials. We first scrutinised all included articles for reference to a trial registry identification number. Secondly, we searched trial registries for trials meeting the same inclusion criteria. We searched the five most commonly used registers for trials published in English, including the Australian and New Zealand Clinical Trial Registry (ANZCTR), ClinicalTrials.gov, International Standard Randomised Controlled Trial Number (ISRCTN) registry, World Health Organisation International Clinical Trials Registry Platform, and the European Union Clinical Trials Register. Key terms used were a combination of “sedentary” OR “sitting” AND “break” or “interrupt” or “activity”. Where possible, results were filtered to include only trials that were “completed”, “interventional”, and/or conducted with “adult/elderly” participants.

Data extraction

Data extraction was performed independently by two reviewers and cross-checked for accuracy. Trial registry number, participant characteristics, and measured outcomes for each trial, recorded separately for registered and non-registered trials, were extracted from the included studies. Information on the number of outcome measures collected, number of outcome measures registered, number of outcome measures ‘registered and reported’, number of outcome measures ‘registered but not reported’, number of outcome measures ‘reported but not registered’, and reported outcomes that were not registered but for which significant results were found in each trial were recorded. Narrative analysis using descriptive statistics was undertaken to describe the nature of the studies and to answer the research questions. Bias definitions are provided alongside the research questions and detailed here.

Potential publication bias was examined by reporting how many published trials had been registered, and of those registered, were all completed trials been published. Any potential duplicate publication bias was observed by carefully examining papers by the same or similar author lists for substantial similarities between participant inclusion criteria, sample sizes, and methods. Possible selective outcome reporting was examined by matching outcomes reported in trial registries to those published. Lastly, any possible risk of Type I error was identified by observing how many different outcomes had been measured in each trial.

Results

Out of 7645 title and abstracts, 69 were eligible for full text screening. Out of the full text papers reviewed, 32 trials reported in 45 papers were included (Fig. 1). The sample sizes per trial ranged from 9 to 70 (Table 1), with a combined total sample of n=606 (289 females, 48%). The mean age of included participants ranged from 21 to 69 years, and trials included a variety of population groups including people who were healthy (n=16), overweight (n=13), had type 2 diabetes (n=2), or post-stroke (n=1). All papers were published between 2012 and 2018, with 36 (80%) published in the last 5 years.

Figure 1.

PRISMA flowchart of the review.

(0.29MB).
Table 1.

Summary of trials and outcomes.

Trial registry no.  Papers  n (trial)  Participant characteristics  Outcomes registered (published outcomes are bolded)  Outcomes reported not registered (outcomes with significant positive between condition differences are italicised) 
ACTRN12613000576729  Dempsey et al. (2015)7Dempsey et al. (2016)8Dempsey et al. (2017)6Grace et al. (2017)11Dempsey et al. (2018)23  24  Type 2 diabetic overweight/obese and inactive adults 10 females (41.7%) 62±6 years  Postprandial glucoseContinuous glucose measurementPostprandial insulinC-peptide analysisBlood pressureFatigue  TriglyceridesOther cholesterolsNorepinephrine/NoradrenalineRespiratory exchange ratioTotal energy expenditureHeart rate 
ACTRN12615001189516  English et al. (2018)22English et al. (2018)10  19  Post-stroke people (between 3 months and 10 years) ambulant with minimal assistance and not taking diabetic medication other than metformin9 females (47.4%)68.2±10.2 years  Postprandial glucoseInsulin controlBlood pressureFibrinogenFeasibility (adherence to protocol including fatigue)  Nil 
ACTRN12609000656235  Larsen et al. (2014)15Latouche et al. (2013)16Dunstan et al. (2012)9Howard et al. (2013)13  19  Overweight/obese adults08 females (42.1%)53.8±4.9 years  Postprandial glucose levelsPostprandial insulin levelsPostprandial free fatty acid levels  Hemostatic parameters (fibrinogen, platelet count, activated partial thromboplastin time, Von Willebrand factor antigen)Haematological parameters (volume, Hct, Hb, RBC, WBC, PC, MPV)Blood pressureHeart rateGene expression 
ACTRN12614000624684  Homer et al. (2017)12Mete et al. (2018)17  36  Healthy, normal weight adults25 females (69.4%)25.4±3.9 years  Postprandial glucosePostprandial insulinPostprandial triglyceridePostprandial NEFASubstrate utilisationEnergy expenditureEnergy intakeAppetite  None 
ACTRN12611000632998  Thorp et al. (2014)19Thorp et al. (2014)20  23  Overweight/obese sedentary office workers06 females (26.1%)48.2±8 years  Postprandial glucosePostprandial insulinPostprandial triglyceridePostprandial free fatty acid levels  FatigueMusculoskeletal discomfortWork productivityWorkstation acceptability 
ACTRN12610000657022  Larsen et al. (2015)14  19  Overweight/obese, sedentary adults08 females (42.1%)56.7±6.5 years  Postprandial glucosePostprandial insulinPostprandial triglyceridesPostprandial free fatty acid  None 
ACTRN12610000953033  Peddie et al. (2013)18  70  Healthy, normal weight adults working in a predominately sedentary occupation42 females (60.0%)25.9±5.3 years  Postprandial glucosePostprandial insulinPostprandial triglycerideBlood pressureSubstrate utilisation  Heart rate 
ACTRN12613000137796  Wennberg et al. (2016)21  19  Overweight/obese adults09 females (47.7%)59.7±8.1 years  Continuous glucose measurementCortisolCatecholaminesExecutive functionMemoryBrain-derived neurotrophic factor, BDNFInterleukin-6, IL-6  InsulinBlood pressureFatigueHeart rate 
ISRCTN48132950  Brocklebank et al. (2017)31  17  Healthy office workers in a predominately sedentary occupation09 females (52.9%)52.4±5.1 years  Postprandial glucosePre-prandial interstitial glucose  None 
NCT02215603  Benatti et al. (2017)24  14  Healthy, physically inactive males14 males (100%)±8.8 years  Postprandial glucoseContinuous glucose measurementPostprandial insulinPostprandial lipidsPostprandial cytokine  C-peptideTotal energy expenditure 
NCT02717377  Bergouignan et al. (2016)25  30  Healthy sedentary adults21 females (70.0%)30±5.6 years  Energy and mood levelCognitive function  Appetite ratingsEpinephrine/AdrenalineNorepinephrine/NoradrenalineDopamineCortisolHeart rate 
NCT00945165  Dijk et al. (2013)26  20  Type 2 diabetic males20 males (100%)64±1 years  HyperglycemiaMean blood glucose  Heart rate 
NCT02135172  Henson et al. (2016)27  22  Postmenopausal, overweight/obese dysglycemic women22 females (100%)66.6±4.7 years  Postprandial glucosePostprandial insulinPostprandial triglyceridesLipoprotein lipase activity  NEFA levels 
NCT02743286  Kerr et al. (2017)28  10  Postmenopausal, overweight/obese and sedentary women10 females (100%)66±9 years  Change in glycemic regulationChange in endothelial functionChange in mitochondrial metabolitesStudy feasibility  Blood pressure 
NCT02493309  McCarthy et al. (2017)29  34  Healthy, non-obese adults working in a predominately sedentary occupation18 females (52.9%)40±9 years  Postprandial glucosePostprandial insulinPostprandial triglyceridesBlood pressure  None 
NCT02909894  McCarthy et al. (2017)30  13  Obese and inactive adults at risk of type 2 diabetes07 females (53.8%)66±6 years  Postprandial glucosePostprandial insulinBlood pressureCognitive function  Mood 
  Holmstrup et al. (2013)41  11  Obese, young adults with impaired fasting glucose03 females (27.2%)25.2±1.3 years  N/A  Postprandial glucosePostprandial insulinC-peptidePeptide YY tAUCHunger and satiety 
  Holmstrup et al. (2014)42         
  Masaki et al. (2015)44  15  Healthy, normo-lipidaemic men15 males (100%)26.80±2 years  N/A  Postprandial glucosePostprandial insulinNEFA levelsOther cholesterolsLPL protein/ApolipproteinOxidative stress markers3-OHB 
  Miyashita et al. (2013)46         
  Mullane et al. (2017)47  09  Overweight/obese and physically inactive (pre-hypertensive or with impaired fasting glucose)07 females (77.8%)30±15 years  N/A  Sleep efficiencyHeart rateCognitive performance 
  Zeigler et al. (2016)50         
  Altenburg et al. (2013)32  11  Healthy young adults06 females (54.5%)21.4 (19.5–23.1) years  N/A  Postprandial glucoseC-peptideTriglyceridesTotal cholesterolHDL cholesterolLDL cholesterolMuscle activity 
  Bailey and Locke (2015)34  10  Healthy, non-obese adults03 females (30.0%)24.0±3 years  N/A  Postprandial glucoseTriglyceridesTotal cholesterolHDL cholesterolBlood pressure 
  Bailey et al. (2016)33  13  Healthy, inactive, sedentary adults07 females (53.8%)26.6±8.5 years  N/A  Postprandial glucosePostprandial insulinPeptide YY tAUCAcylated ghrelin tAUCAppetite ratingsEnergy intake 
  Barone Gibbs et al. (2017)35  25  Overweight/obese adults with pre to stage 1 hypertension09 females (36.0%)42±12 years  N/A  Blood pressurePulsed wave velocityHeart rate 
  Bhammar et al. (2017)36  10  Overweight/obese and physically inactive adults05 females (50.0%)32±5 years  N/A  Postprandial glucoseBlood pressure 
  Carter and Gladwell (2017)37  10  Healthy adults04 females (40.0%)27.3±8.1 years  N/A  Blood pressureEndothelial functionShear rate 
  Engeroff et al. (2017)38  18  Healthy young premenopausal women18 females (100%)25.6±2.6 years  N/A  Total cholesterolHDL cholesterolLDL cholesterol 
  Hansen et al. (2016)39  14  Healthy young, normal weight and recreationally active adults08 females (57.1%)22 (20 – 23) years  N/A  Postprandial glucose 
  Hawari et al. (2016)40  10  Overweight/obese, normoglycaemic males10 males (100%)33±13 years  N/A  Postprandial glucosePostprandial insulinTriglyceridesSubstrate oxidationTotal energy expenditure 
  Kim et al. (2014)43  09  Healthy young recreationally active males09 males (100%)24±4 years  N/A  Postprandial glucosePostprandial insulinTriglyceridesOther cholesterolsSubstrate oxidationRespiratory exchange ratio 
  Miyashita et al. (2016)45  15  Postmenopausal women15 females (100%)68.8±3.2 years  N/A  Postprandial glucosePostprandial insulinTriglyceridesNEFA levelsRating of perceived exertionHeart rate3-OHB 
  Pulsford et al. (2017)48  25  Healthy, inactive, weight stable males25 males (100%)40.2±12.2 years  N/A  Postprandial glucoseMatsuda indexPostprandial insulin 
  Thosar et al. (2015)49  12  Healthy inactive young non-obese males12 males (100%)24.2±4.2 years  N/A  Flow mediated dilationShear rate 

Abbreviations: ACTRN, Australian New Zealand clinical trials registry; Hb, haemoglobin; Hct, haematocrit; HDL, high-density lipoproteins; ISRCTN, international standard randomised controlled trials number; LDL, low-density lipoproteins; LPL, lipoprotein lipase; MPV, mean platelet volume; N/A, not applicable; NCT, national clinical trial; NEFA, non-esterified fatty acids; PC, platelet count; RBC, red blood cell count; tAUC, total area under the curve WBC, white blood cell count; 3-OHB, 3-hydroxybutyra.

How many published trials are registered, and of those registered, have all completed trials been published?

Only 16 (50%) of published trials were registered (Table 1) in registries including the ANZTR (n=86–23), ClinicalTrials.gov (n=724–30), and ISRCTN (n=131). The remaining 16 (50%) trials (published in 19 papers) were not registered.32–50 All registered trials were completed and published (Fig. 2).

Figure 2.

Flowchart of the included studies.

(0.34MB).
Are duplicate publications from the same trial easily identifiable?

Outcomes from the 16 registered trials were published in 26 papers. In all of these papers either a trial registration number was quoted or the authors clearly identified that the paper was reporting additional outcomes from a primary study. Identifying duplicate publications from the unregistered trials was more difficult. For three trials,41,42,44,46,47,50 similarities in the sample size and participant demographics across papers was suggestive of duplicate publication. We were unable to definitively determine how many of the remaining 13 unregistered trials were duplicate versus singular publications (Fig. 2).

Are all outcomes recorded in trial registries published?

Of the registered trials, a total of 70 outcomes were registered, and of these, results from 53 (76%) were published. Eleven (69%) registered trials had at least one outcome measure that was registered but the results not published, and 11 (69%) of the trials included results from additional outcomes that were not prospectively registered (Fig. 2). Published studies rarely specified whether the outcomes reported were primary or secondary measures. As 50% of trials were not registered, the degree to which outcome reporting bias is present (e.g. due to the upgrading secondary outcomes to primary outcomes and vice versa) could not be established.

How many different outcomes have been measured in each trial?

A total of 46 different outcomes (out of 53 reported outcome measures, some similar outcome measures were collated. e.g.: high density lipids, low density lipids and total cholesterol were combined as postprandial lipids) were reported across all trials (including registered and unregistered trials), the majority (31 [67%]) being collected in ≤ 2 trials (Fig. 3). The number of outcomes collected per trial ranged from 1 to 12 (mean 5 [SD 3]). The most commonly measured outcomes were postprandial glucose (26 [81%]), postprandial insulin (21 [66%]), and triglycerides (13 [41%]) (Table 1). Across all the registered trials, results from 32 additional outcomes not mentioned in trial registry records were published. Of these additional outcomes 22 (69%) reported positive, significant between-condition differences (Table 1).

Figure 3.

Frequency of different outcomes measured in included trials.

(0.37MB).
Discussion

We conducted systematic searches of databases and trial registries to investigate the issues in trial registration in experimental trials investigating the effect of interrupting prolonged periods of sitting time with frequent, short bouts, of physical activity or standing. We found direct evidence of issues in trial registration which may lead to publication bias. All completed registered trials were published. However, our finding that only half of all published trials were registered creates uncertainty concerning the number of other unregistered trials which may also remain unpublished. Similarly, while there was no direct evidence of selective reporting (results from all registered outcomes have been published), 70% of registered trials published results from additional outcomes that were not registered. The search revealed that more than half of the published, non-registered outcomes reported statistically significant positive findings. However, this may be because some reported outcomes reflect the use of new technologies or techniques that may not have been present at the time of registration, particularly for some earlier studies that used metabolomics data. It is important to note that we chose to focus on the field of experimental sedentary behaviour research, given most papers were published after trial registration became common practice. It is possible that similar issues exist in other fields of research, including those with a longer publication history such as physical activity research.

More than half of the trials were not registered, making it difficult to thoroughly assess the degree of publication bias in the literature. This is an issue not limited to the field of sedentary behaviour research. Several previous reviews of randomised controlled trials published in medical journals in the past decade have found between 25 and 50% of trials were not registered, even those published in high impact factor journals.51,52 When trials are not registered, it is impossible to know what additional outcomes were measured but not reported. Selective reporting of the collected outcomes could be influenced by the significance of the results,53,54 leading to potentially misleading evidence.1 We found that the majority of non-registered outcomes for which findings were published had significant, positive findings, lending weight to this concern. Many authors favour submitting their work with positive results for publication and many editors prefer to publish significant results.55,56 To mitigate against this risk, it is good practice that effect sizes and confidence intervals for all outcomes are reported, regardless of the significance of the findings. Journal editors can assist in addressing this issue by giving equal consideration to papers reporting non-significant findings, particularly where trials are adequately powered to show an effect. Moreover, conflict of interests such as connections with related industries may be another potential contributing factor to publication bias.

Finally, the large number of different outcomes measured across trials warrants greater attention in future trials. While this is perhaps not surprising, given the field of the physiology of sedentary behaviour is still relatively young, and much of the research remains exploratory in nature, care must be taken to guard against potentially spurious findings. For future trials we recommend careful selection of outcomes, with a clear biological rationale for each and a single, pre-registered primary outcome with sufficient statistical power, as recommended by the CONSORT statement. Consideration should be given to adjusting analyses for multiple comparisons where this is appropriate.3 The reporting of any additional outcomes, particularly those with insufficient statistical power or that were not prospectively registered, should clearly identify that the analyses were exploratory in nature. Additionally, reaching consensus on a core outcome dataset for sedentary behaviour research, as has been done in other fields57 would be a useful step forward. We also suggest researchers conduct two separate analyses for registered and non-registered trials in future systematic reviews.52 Future reviews may also consider investigating which factors (such as study design, methodological quality, and impact factor of the journals) were associated with registering or not registering trials. Furthermore, in future reviews it would be interesting to investigate if outcomes have been upgraded (i.e., from secondary outcome in the register to primary outcome in the published trial), or downgraded, and if these modifications were made in light of the results of the trial. This was not possible to do in our review as many registered trials did not clearly state a single primary outcome variable. It is important that future trials pre-register a clearly defined single primary outcome measure.6,7,11

The strengths of this study included a comprehensive search strategy, including all relevant databases and trial registries. Moreover, the independent data extraction between two authors adds further rigour to our work. Limitations include excluding trials not published in English, excluding conference abstracts and grey literature. While we included a consultation phase, it is possible that some recent papers may still have been missed. By only searching the five most commonly used trial registries, it is possible that some trial registrations may have been missed. However, no published trials reported registration numbers from registries other than those we searched, making this unlikely. We also acknowledge that the search strategy was developed to address the research objectives of the previous published scoping review, therefore we did not include searches of unpublished studies. While we are confident that we have included all relevant literature at the time period of search, further studies may have been published since. In addition, this review was designed to provide a broad overview of evidence on issues in trial registration which may lead to publication bias, selective reporting, and risk of Type I error in experimental studies investigating the effect of frequent activity interruptions to prolonged sitting time and therefore did not report on the magnitude or direction of the findings.

Conclusion

We found a lack of widespread trial registration, which may lead to publication bias and selective reporting among experimental trials investigating the effect of interrupting prolonged periods of sitting time with frequent, short bouts, of physical activity. To further strengthen confidence in this field, we recommend that all trials are prospectively registered, trial registration numbers are clearly stated in all publications along with explicit reference to other papers reporting results from the same dataset, trials are adequately powered for a primary outcome and exploratory analyses of secondary outcomes are clearly identified as such, and finally that the development of a core outcome dataset for the field is prioritised.

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgements

This paper presents independent research funded by the National Institute for Health Research (NIHR) under its Programme Grants for Applied Research Programme (Development and evaluation of strategies to reduce sedentary behaviour in patients after stroke and improve outcomes, Reference number RP-PG-0615-20019). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care, UK.

Associate Professor English was supported by a National Heart Foundation Future Leaders Fellowship (#101177). Professor Dunstan is supported by a National Health and Medical Research Council of Australia (NHMRC) Senior Research Fellowship (# 1078360), an NHMRC Centre for Research Excellence Grant (# 1057608) and by the Victorian Government's Operational Infrastructure Support Program. Dr Janssen was supported by a New South Wales Department of Health Early Career Researcher Fellowship.

References
[1]
Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011],
[2]
J. Kleijnen, P. Knipschild.
Review articles and publication bias.
Arzneimittelforschung, 42 (1992), pp. 587-591
[3]
R. Bender, S. Lange.
Adjusting for multiple testing – when and how?.
J Clin Epidemiol, 54 (2001), pp. 343-349
[4]
S.F.M. Chastin, M. De Craemer, K. De Cocker, et al.
How does light-intensity physical activity associate with adult cardiometabolic health and mortality? Systematic review with meta-analysis of experimental and observational studies.
[5]
P. Mackie, I. Weerasekara, G. Crowfoot, et al.
What is the effect of interrupting prolonged sitting with frequent bouts of physical activity or standing on first or recurrent stroke risk factors?. a scoping review.
PLOS ONE, 14 (2019), pp. e0217981
[6]
P. Dempsey, J. Blankenship, R. Larsen, et al.
Interrupting prolonged sitting in type 2 diabetes: nocturnal persistence of improved glycaemic control.
Diabetologia, 60 (2017), pp. 499-507
[7]
P. Dempsey, R. Larsen, P. Sethi, et al.
Benefits for type 2 diabetes of interrupting prolonged sitting with brief bouts of light walking or simple resistance activities.
Diabetes Care, 39 (2016), pp. 964-972
[8]
P.C. Dempsey, J.W. Sacre, R.N. Larsen, et al.
Interrupting prolonged sitting with brief bouts of light walking or simple resistance activities reduces resting blood pressure and plasma noradrenaline in type 2 diabetes.
J Hypertens, 34 (2016), pp. 2376-2382
[9]
D. Dunstan, B. Kingwell, R. Larsen, et al.
Breaking up prolonged sitting reduces postprandial glucose and insulin responses.
Diabetes Care, 35 (2012), pp. 976-983
[10]
C. English, H. Janssen, G. Crowfoot, et al.
Breaking up sitting time after stroke (BUST-stroke).
Int J Stroke, (2018),
[11]
M.S. Grace, P.C. Dempsey, P. Sethi, et al.
Breaking up prolonged sitting alters the postprandial plasma lipidomic profile of adults with type 2diabetes.
J Clin Endocrinol Metab, 102 (2017), pp. 1991-1999
[12]
A.R. Homer, S.P. Fenemor, T.L. Perry, et al.
Regular activity breaks combined with physical activity improve postprandial plasma triglyceride, nonesterified fatty acid, and insulin responses in healthy, normal weight adults: a randomized crossover trial.
J Clin Lipidol, 11 (2017), pp. 1268-1279
[13]
B. Howard, S. Fraser, P. Sethi, et al.
Impact on hemostatic parameters of interrupting sitting with intermittent activity.
Med Sci Sports Exerc, 45 (2013), pp. 1285-1291
[14]
R. Larsen, B. Kingwell, C. Robinson, et al.
Breaking up of prolonged sitting over three days sustains, but does not enhance, lowering of postprandial plasma glucose and insulin in overweight and obese adults.
Clin Sci, 129 (2015), pp. 117-127
[15]
R. Larsen, B. Kingwell, P. Sethi, E. Cerin, N. Owen, D. Dunstan.
Breaking up prolonged sitting reduces resting blood pressure in overweight/obese adults.
Nutr Metab Cardiovasc Dis, 24 (2014), pp. 976-982
[16]
C. Latouche, J. Jowett, A. Carey, et al.
Effects of breaking up prolonged sitting on skeletal muscle gene expression.
J Appl Physiol, 114 (2013), pp. 453-460
[17]
E.M. Mete, T.L. Perry, J.J. Haszard, et al.
Interrupting prolonged sitting with regular activity breaks does not acutely influence appetite: a randomised controlled trial.
[18]
M. Peddie, J. Bone, N. Rehrer, C. Skeaff, A. Gray, T. Perry.
Breaking prolonged sitting reduces postprandial glycemia in healthy, normal-weight adults: a randomized crossover trial.
Am J Clin Nutr, 98 (2013), pp. 358-366
[19]
A. Thorp, B. Kingwell, N. Owen, D. Dunstan.
Breaking up workplace sitting time with intermittent standing bouts improves fatigue and musculoskeletal discomfort in overweight/obese office workers.
Occup Environ Med, 71 (2014), pp. 765-771
[20]
A. Thorp, B. Kingwell, P. Sethi, L. Hammond, N. Owen, D. Dunstan.
Alternating bouts of sitting and standing attenuate postprandial glucose responses.
Med Sci Sports Exerc, 46 (2014), pp. 2053-2061
[21]
P. Wennberg, C.J. Boraxbekk, M. Wheeler, et al.
Acute effects of breaking up prolonged sitting on fatigue and cognition: a pilot study.
BMJ Open, 6 (2016), pp. e009630
[22]
C. English, H. Janssen, G. Crowfoot, et al.
Frequent, short bouts of light-intensity exercises while standing decreases systolic blood pressure: breaking up sitting time after stroke (BUST-Stroke) trial.
Int J Stroke, 13 (2018), pp. 932-940
[23]
P.C. Dempsey, D.W. Dunstan, R.N. Larsen, G.W. Lambert, B.A. Kingwell, N. Owen.
Prolonged uninterrupted sitting increases fatigue in type 2 diabetes.
Diabetes Res Clin Pract, 135 (2018), pp. 128-133
[24]
F.B. Benatti, S.A. Larsen, K. Kofoed, et al.
Intermittent standing but not a moderate exercise bout reduces postprandial glycemia.
Med Sci Sports Exerc, 49 (2017), pp. 2305-2314
[25]
A. Bergouignan, K.T. Legget, N. De Jong, et al.
Effect of frequent interruptions of prolonged sitting on self-perceived levels of energy, mood, food cravings and cognitive function.
Int J Behav Nutr Phys Act, 13 (2016), pp. 113
[26]
J. Dijk, M. Venema, W. Mechelen, C. Stehouwer, F. Hartgens, L. Loon.
Effect of moderate-intensity exercise versus activities of daily living on 24-hour blood glucose homeostasis in male patients with type 2 diabetes.
Diabetes Care, 36 (2013), pp. 3448-3453
[27]
J. Henson, M. Davies, D. Bodicoat, et al.
Breaking up prolonged sitting with standing or walking attenuates the postprandial metabolic response in postmenopausal women: a randomized acute study.
Diabetes Care, 39 (2016), pp. 130-138
[28]
J. Kerr, K. Crist, D.G. Vital, et al.
Acute glucoregulatory and vascular outcomes of three strategies for interrupting prolonged sitting time in postmenopausal women: a pilot, laboratory-based, randomized, controlled, 4-condition, 4-period crossover trial.
PLoS ONE, 12 (2017), pp. e0188544
[29]
M. McCarthy, C.L. Edwardson, M.J. Davies, et al.
Fitness moderates glycemic responses to sitting and light activity breaks.
Med Sci Sports Exerc, 49 (2017), pp. 2216-2222
[30]
M. McCarthy, C.L. Edwardson, M.J. Davies, et al.
Breaking up sedentary time with seated upper body activity can regulate metabolic health in obese high-risk adults: a randomized crossover trial.
Diabetes Obes Metab, 19 (2017), pp. 1732-1739
[31]
L.A. Brocklebank, R.C. Andrews, A. Page, C.L. Falconer, S. Leary, A. Cooper.
The acute effects of breaking up seated office work with standing or light-intensity walking on interstitial glucose concentration: a randomized crossover trial.
J Phys Act Health, 14 (2017), pp. 617-625
[32]
T. Altenburg, J. Rotteveel, D. Dunstan, J. Salmon, M. Chinapaw.
The effect of interrupting prolonged sitting time with short, hourly, moderate-intensity cycling bouts on cardiometabolic risk factors in healthy, young adults.
J Appl Physiol, 115 (2013), pp. 1751-1756
[33]
D. Bailey, D. Broom, B. Chrismas, L. Taylor, E. Flynn, J. Hough.
Breaking up prolonged sitting time with walking does not affect appetite or gut hormone concentrations but does induce an energy deficit and suppresses postprandial glycaemia in sedentary adults.
Appl Physiol Nutr Metab, 41 (2016), pp. 324-331
[34]
D. Bailey, C. Locke.
Breaking up prolonged sitting with light-intensity walking improves postprandial glycemia, but breaking up sitting with standing does not.
J Sci Med Sport, 18 (2015), pp. 294-298
[35]
B. Barone Gibbs, R.J. Kowalsky, S.J. Perdomo, J.M. Taormina, J.R. Balzer, J.M. Jakicic.
Effect of alternating standing and sitting on blood pressure and pulse wave velocity during a simulated workday in adults with overweight/obesity.
J Hypertens, 35 (2017), pp. 2411-2418
[36]
D.M. Bhammar, B.J. Sawyer, W.J. Tucker, G.A. Gaesser.
Breaks in sitting time: effects on continuously monitored glucose and blood pressure.
Med Sci Sports Exerc, 49 (2017), pp. 2119-2130
[37]
S.E. Carter, V.F. Gladwell.
Effect of breaking up sedentary time with callisthenics on endothelial function.
J Sports Sci, 35 (2017), pp. 1508-1514
[38]
T. Engeroff, E. Fuzeki, L. Vogt, W. Banzer.
Breaking up sedentary time, physical activity and lipoprotein metabolism.
J Sci Med Sport, 20 (2017), pp. 678-683
[39]
R. Hansen, J. Andersen, A. Vinther, U. Pielmeier, R. Larsen.
Breaking up prolonged sitting does not alter postprandial glycemia in young, normal-weight men and women.
Int J Sports Med, 37 (2016), pp. 1097-1102
[40]
N.S.A. Hawari, I. Al-Shayji, J. Wilson, J.M.R. Gill.
Frequency of breaks in sedentary time and postprandial metabolic responses.
Med Sci Sports Exerc, 48 (2016), pp. 2495-2502
[41]
M. Holmstrup, T. Fairchild, S. Keslacy, R. Weinstock, J. Kanaley.
Satiety, but not total PYY, Is increased with continuous and intermittent exercise.
Obesity, 21 (2013), pp. 2014-2020
[42]
M. Holmstrup, T. Fairchild, S. Keslacy, R. Weinstock, J. Kanaley.
Multiple short bouts of exercise over 12-h period reduce glucose excursions more than an energy-matched single bout of exercise.
Metabolism, 63 (2014), pp. 510-519
[43]
I.-Y. Kim, S. Park, J.R. Trombold, E.F. Coyle.
Effects of moderate- and intermittent low-intensity exercise on postprandial lipemia.
Med Sci Sports Exerc, 46 (2014), pp. 1882-1890
[44]
T. Masaki, M. Masashi, P. Jong-Hwan, S. Shizuo, S. Katsuhiko.
Effects of breaking sitting by standing and acute exercise on postprandial oxidative stress.
Asian J Sports Med, 6 (2015), pp. 1-5
[45]
M. Miyashita, K. Edamoto, T. Kidokoro, et al.
Interrupting sitting time with regular walks attenuates postprandial triglycerides.
Int J Sports Med, 37 (2016), pp. 97-103
[46]
M. Miyashita, J. Park, M. Takahashi, K. Suzuki, D. Stensel, Y. Nakamura.
Postprandial lipaemia: effects of sitting, standing and walking in healthy normolipidaemic humans.
Int J Sports Med, 34 (2013), pp. 21-27
[47]
S.L. Mullane, M.P. Buman, Z.S. Zeigler, N.C. Crespo, G.A. Gaesser.
Acute effects on cognitive performance following bouts of standing and light-intensity physical activity in a simulated workplace environment.
J Sci Med Sport, 20 (2017), pp. 489-493
[48]
R. Pulsford, J. Blackwell, M. Hillsdon, K. Kos.
Intermittent walking, but not standing, improves postprandial insulin and glucose relative to sustained sitting: a randomised cross-over study in inactive middle-aged men.
J Sci Med Sport, 20 (2017), pp. 278-283
[49]
S. Thosar, S. Bielko, K. Mather, J. Johnston, J. Wallace.
Effect of prolonged sitting and breaks in sitting time on endothelial function.
Med Sci Sports Exerc, 47 (2015), pp. 843-849
[50]
Z. Zeigler, S. Mullane, N. Crespo, M. Buman, G. Gaesser.
Effects of standing and light-intensity activity on ambulatory blood pressure.
Med Sci Sports Exerc, 48 (2016), pp. 175-181
[51]
S. Mathieu, I. Boutron, D. Moher, D.G. Altman, P. Ravaud.
Comparison of registered and published primary outcomes in randomized controlled trials.
JAMA, 302 (2009), pp. 977-984
[52]
L. Trinquart, A.G. Dunn, F.T. Bourgeois.
Registration of published randomized trials: a systematic review and meta-analysis.
[53]
I.F. Tannock.
False-positive results in clinical trials: multiple significance tests and the problem of unreported comparisons.
J Natl Cancer Inst, 88 (1996), pp. 206-207
[54]
R.C. Macefield, C.E. Boulind, J.M. Blazeby.
Selecting and measuring optimal outcomes for randomised controlled trials in surgery.
Langenbeck's Arch Surg, 399 (2014), pp. 263-272
[55]
A. Mlinarić, M. Horvat, V. Šupak Smolčić.
Dealing with the positive publication bias: why you should really publish your negative results.
Biochem Med, 27 (2017), pp. 030201
[56]
Y. Tsujimoto, Y. Tsutsumi, Y. Kataoka, et al.
Association between statistical significance and time to publication among systematic reviews: a study protocol for a meta-epidemiological investigation.
[57]
G. Kwakkel, N.A. Lannin, K. Borschmann, et al.
Standardized measurement of sensorimotor recovery in stroke trials: consensus-based core recommendations from the stroke recovery and rehabilitation roundtable.
Neurorehabil Neural Repair, 31 (2017), pp. 784-792
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