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Randomised controlled trials (RCTs) in sports injury research: authors—please report the compliance with the intervention
  1. Rasmus Oestergaard Nielsen1,
  2. Michael Lejbach Bertelsen1,
  3. Daniel Ramskov2,
  4. Camma Damsted1,
  5. Evert Verhagen3,
  6. Steef W Bredeweg4,
  7. Daniel Theisen5,
  8. Laurent Malisoux6
  1. 1 Department of Public Health, Section for Sport Science, Aarhus University, Aarhus, Denmark
  2. 2 Department of Physiotherapy, University College of Northern Denmark, Aalborg, Denmark
  3. 3 Department of Public and Occupational Health, EMGO Institute for Health and Care Research, Amsterdam, Netherlands
  4. 4 Center for Sports Medicine, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
  5. 5 ALAN—Maladies Rares Luxembourg, Bascharage, Luxembourg
  6. 6 Sports Medicine Research Laboratory, Luxembourg Institute of Health, Luxembourg, Luxembourg
  1. Correspondence to Dr Rasmus Oestergaard Nielsen, Department of Public Health, Section for Sports Science, Aarhus University, Aarhus 8000, Denmark; roen{at}


Background In randomised controlled trials (RCTs) of interventions that aim to prevent sports injuries, the intention-to-treat principle is a recommended analysis method and one emphasised in the Consolidated Standards of Reporting Trials (CONSORT) statement that guides quality reporting of such trials. However, an important element of injury prevention trials—compliance with the intervention—is not always well-reported. The purpose of the present educational review was to describe the compliance during follow-up in eight large-scale sports injury trials and address compliance issues that surfaced. Then, we discuss how readers and researchers might consider interpreting results from intention-to-treat analyses depending on the observed compliance with the intervention.

Methods Data from seven different randomised trials and one experimental study were included in the present educational review. In the trials that used training programme as an intervention, we defined full compliance as having completed the programme within ±10% of the prescribed running distance (ProjectRun21 (PR21), RUNCLEVER, Start 2 Run) or time-spent-running in minutes (Groningen Novice Running (GRONORUN)) for each planned training session. In the trials using running shoes as the intervention, full compliance was defined as wearing the prescribed running shoe in all running sessions the participants completed during follow-up.

Results In the trials that used a running programme intervention, the number of participants who had been fully compliant was 0 of 839 (0%) at 24-week follow-up in RUNCLEVER, 0 of 612 (0%) at 14-week follow-up in PR21, 12 of 56 (21%) at 4-week follow-up in Start 2 Run and 8 of 532 (1%) at 8-week follow-up in GRONORUN. In the trials using a shoe-related intervention, the numbers of participants who had been fully compliant at the end of follow-up were 207 of 304 (68%) in the 21 week trial, and 322 of 423 (76%), 521 of 577 (90%), 753 of 874 (86%) after 24-week follow-up in the other three trials, respectively.

Conclusion The proportion of runners compliant at the end of follow-up ranged from 0% to 21% in the trials using running programme as intervention and from 68% to 90% in the trials using running shoes as intervention. We encourage sports injury researchers to carefully assess and report the compliance with intervention in their articles, use appropriate analytical approaches and take compliance into account when drawing study conclusions. In studies with low compliance, G-estimation may be a useful analytical tool provided certain assumptions are met.

  • Injury
  • Randomised controlled trial
  • Methodology

Statistics from


  • Contributors DR collected data for the RUNCLEVER, CD for PR21, MLB for Start 2 Run, SWB for GRONORUN and LM and DT for the shoe-related trials. LM and MLB analysed the data. RON drafted the manuscript, while the remaining co-authors revised it for important intellectual content.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The study protocols for the running programme trials were approved by the local ethics committees: Groningen Novice Running (Medical Ethics Committee of the University Medical Center Groningen, The Netherlands ISRCTN37259753), RUNCLEVER (Northern Denmark Region N-20140069), ProjectRun21 (Central Denmark Region 187/2015), and Start 2 Run (Northern Denmark Region N-20160031). The study protocols for the shoe-related trials have previously been approved by the National Ethics Committee for Research in Luxembourg (ref.: 201201/02, 201211/04, 201407/09 V1.1, 201701/02 V1.1, respectively, for study 1–4). Prior to data collections, all trials were approved from the local ethics committees and from the data protection agencies.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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