A randomised controlled trial (RCT) with a follow-up period of five months (March 2017 – July 2017) was conducted. The design of this study is described in detail elsewhere13. The study design and protocol were approved by the Medical Ethics Review Committee of the Academic Medical Center (W16_335 # 16.417; Amsterdam, the Netherlands). The trial is registered in the Dutch Trial Registry (ID: NL6225).
The group of participants consisted of adult novice runners. Inclusion criteria were: (i) aged 18 and older; (ii) having less than one year of running experience and/or not considering themselves as an experienced or very experienced runner. Participants were recruited via social media networks (Facebook, websites, Twitter, LinkedIn, newsletters) of the participating organizations. Participants who completed all questionnaires were entered into a draw offering a possibility to win a gift voucher to the value of €200 for running clothes. All participants of the study provided informed consent online.
Participants within the intervention group obtained access to the Runfitcheck intervention13. No further conditions were applied to the use of the intervention. The Runfitcheck intervention was developed according to an evidence-based (Knowledge Transfer Scheme and Intervention Mapping) and practice-based (running experts) approach to stimulate injury-preventive behaviour among novice runners. Through an expert consultation and research process, two main dimensions in the risk for RRIs were identified: (1) the physical load-taking capacity of runners; and (2) the motivation of runners to achieve their running goals. Across these two domains, runners were classified into four categories: (1) a low physical load-taking capacity and a low goal-orientation; (2) a low physical load-taking capacity and a high goal-orientation; (3) a high physical load-taking capacity and a low goal-orientation; and (4) a high physical load-taking capacity and a high goal-orientation. Depending on their classification, runners directly received tailored advice on the website for achieving optimal running practice. This advice consisted of: 1) advice about the use of a training schedule based on the runner’s load-taking capacity and motivation. Runners could also subscribe to receive a personalised running schedule for 6 or 12 weeks (0–3 KM, 0–5 KM, 3–5 KM, 5–10 KM, 10–16 KM). The running schedules were amplified on the runner’s load-taking capacity, motivation, and specified time frame until a running event; 2) Four exercises to be performed three times a week to increase strength or improve running technique (plank, skipping, tripling, and leaping sideways on two legs), and the possibility to receive a more varied training programme based on load-taking capacity; 3) An instruction video with voice-over and additional information on performing a warm-up. The warm-up routine consisted of tripling, one-leg skipping, normal skipping, heel-to-buttocks exercise, squats, good mornings, lunges, six different leaping exercises, skating jumps, six different one-leg leaping exercises, squats with arm swing, and high jumps. More information on the development process and content of the Runfitcheck is described in detail elsewhere14. The participants in the control group performed their running activities as usual.
The main outcome measure of the study was injury-preventive behaviour, being operationalised as: (i) using a (personalised) training schedule; (ii) performing strength and technique exercises15; and (iii); performing a warm-up prior to running16. Each of these injury-preventive behaviours was divided into preparatory and executional actions:
training schedule consisted of two preparatory and one executional action, namely: searching for a training schedule, creating a personal training schedule, using a general training schedule.
strength and technique exercises consisted of two preparatory and two executional actions: searching for both strength and technique exercises, and executing both strength and technique exercises.
the warm-up consisted of one preparatory and two executional actions: searching for information about a warm-up routine for runners, performing a warm-up routine (extensive or otherwise), and adding strength exercises to a warm-up An extensive warm-up is a warm-up routine in which the runner starts at a slow pace, performs strength exercises and sport-specific All injury-preventive behaviours were assessed through single-answer questions (Yes/No/Not applicable).
Participants were asked to fill in four online questionnaires (T0-T3). At enrolment (T0), participants were asked to report the injury-preventive behaviour (warm-up routine, strength and technique exercises, use of a (personalised) training schedule) they usually performed before or during their running activities. Additionally, participants were asked about their demographic characteristics (age in years, gender), running experience (in months), frequency per week of running and other sports activities in the previous three months, and other injury-preventive behaviour. One month after T0 (T1), three months after T0 (T2), and five months after T0 (T3), participants were asked to retrospectively report in detail, via an online questionnaire, what they had done in that time frame (past month, past two months, past two months, respectively) in terms of preparatory and executional actions during their running activities.
In previous literature, a 12.6% increase in injury-preventive behaviour among recreational adult runners (in this case, the inclusion of a warm-up) was found during a three-month follow-up period7. Therefore, in this study, it was hypothesized that the Runfitcheck intervention could lead to a 10% difference in favourable injury-preventive behaviour in the intervention group in comparison to the control group. A choice was made to use the word difference instead of increase, as a difference between the two groups was considered as more important than an increase only. For example, if more runners in the intervention group execute the favourable injury-preventive behaviour, but runners in the control group change their behaviour as well, an increase will be found, but this is unlikely to be a statistically significant difference.
To achieve 80% power with a significance level of 0.05, the sample size calculation revealed that 384 participants per study group were needed in this study. Considering a response rate of 85% and a drop-out rate of 10% over the five-month follow-up period, a total of at least 1,000 participants (500 per study group) in this study needed to be approached.
As our main outcome measure injury-preventive behaviour was divided in three different behaviours with several preparatory and executional actions, participants could perform one part of the outcome measure (e.g. performing a warm-up routine), while they did not perform the other behaviours. Hence, after T0, all eligible participants were included in the study, and allocated at random to the intervention or control group after T0 simultaneously, using a computerized random number generator (the Aselect function in Excel). No restrictions were imposed to achieve a balance between groups in size or characteristics for the allocation, and simple randomization was performed. Concealed allocation was used. All steps in the randomization process were performed by the principal researcher. Neither participants in the intervention group nor researchers were blinded in this study.
Descriptive analyses (mean, standard deviation, frequency) were conducted for the different baseline variables in both study groups. Baseline variables were analysed for differences between the intervention and control groups (chi square test, independent T-tests).
For the executional actions, structural behavioural change was evaluated. A behaviour change is regarded as structural if runners changed their behaviour at a certain point in time, and continued to execute the behaviour till the end of the follow-up period, or if runners executed the behaviour at baseline, and continued to execute the behaviour till the end of the follow-up period.
Relative Risks ((RR) and 95% Confidence Interval (95%CI)) were calculated using the risk estimates within the chi square analyses (only available for a 2 × 2 table) and were used to analyse behavioural change in the preparatory and executional injury-preventive actions between T0 and T3. Analyses were performed according to the intention to treat analyses: (i) using a (personalised) training schedule; (ii) performing strength and technique exercises; (iii) performing a warm-up routine (extensive or otherwise). Participants were included in the study until they dropped out, or after completing all four questionnaires. Missing data were not imputed.
For the analyses, those participants who executed the desired behaviour at baseline, and those participant who did not execute the desired behaviour at enrolment, but did execute the desired behaviour during the follow-up period were grouped together and compared with participants who did not execute the desired behaviour at enrolment, and did not start or execute the desired behaviour during the follow-up period.
In sub analyses, participants only were included if they did not perform the favourable injury-preventive behaviour at enrolment. Relative Risks and 95%CI, were performed to reveal the ‘actual effect’ of the intervention on injury-preventive behaviour.
For all analyses, significance was accepted at p < 0.05.