Compliance affects injury prevention study outcomes, but is ill measured ...

When establishing the effectiveness of any injury prevention intervention, knowledge about which percentage of the studied population complied with the prescribed protocol is required. Especially in an intention-to-treat (ITT) approach, insights into the compliance to the intervention provides valuable and, arguably, necessary information to judge the efficacy and effectiveness of an intervention. However, to date, it is unclear to what extent RCTs on sport injury prevention have addressed compliance measures. Therefore, the objective of this systematic review was to assess the extent to which sport injury prevention trials defined, measured and adjusted results for compliance with an injury prevention intervention.

An electronic search was performed in MEDLINE, PubMed, the Cochrane Center of Controlled Trials, CINAHL (Cumulative Index to Nursing and Allied Health Literature), PEDro (Physiotherapy Evidence Database) and SPORTDiscus. English RCTs, quasi-RCTs and cluster- RCTs were considered eligible. Trials that involved physically active individuals or examined the effects of an intervention aimed at the prevention of sports or physical activity related injuries were included.

Of the total of 100 studies included, 71.6 % mentioned compliance or a related term, 68.8 % provided details on compliance measurement and 51.4 % provided compliance data. Only 19.3 % analysed the effect of compliance rates on study outcomes. While studies used heterogeneous methods, pooled effects could not be presented.

Annual trends in compliance reporting. Note A study can be categorised into more than one of the four categories shown

Studies that account for compliance demonstrated that compliance significantly affects study outcomes. The way compliance is dealt with in preventions studies is subject to a large degree of heterogeneity. Valid and reliable tools to measure and report compliance are needed and should be matched to a uniform definition of compliance. 

van Reijen M, Vriend I, Mechelen WV, Finch CF, Verhagen E. Compliance with Sport Injury Prevention Interventions in Randomised Controlled Trials: A Systematic Review. Sports Med. 2016 Feb 11: 1–15.

The full article can be found here (open access)