Background In addition to beneficial health effects, running is associated with a risk of sustaining injuries. The online intervention Runfitcheck was developed to stimulate injury-preventive behaviour among adult novice runners.

Objective To evaluate the effectiveness of Runfitcheck on injury-preventive behaviour among adult novice runners.

Design Randomized controlled trial.

Setting Participants were recruited via Dutch social media networks. Participants were asked to fill in four online questionnaires.

Participants The group of participants consisted of adult novice runners.

Interventions (or Assessment of Risk Factors) The intervention group had access to the Runfitcheck intervention, while the control group performed their running activities as usual.

Main Outcome Measurements Injury-preventive behaviour: (i) using a (personalised) training schedule; (ii) performing strength and technique exercises; and (iii) performing a warm-up routine prior to running. Relative Risks ((RR) and 95% Confidence Interval (95%CI)) were used to analyse behavioural change among runners who were not performing the favourable behaviour at enrolment.

Results A total of 1,411 novice runners (72.6% female, mean age 38.1 years) were included. Runners in the intervention group searched more often for information about a warm-up routine (53.6% versus 33.6%; n=194; RR 1.444 (95%CI 1.098–1.901)), performed a regular warm-up routine more often (47.1% versus 28.4%; n= 196; RR 1.461 (95%CI 1.084–1.968), and added strength exercises to their warm-up routine more often than runners in the control group (32.6% versus 17.4%; n=192; RR 1.504 (95%CI 1.039–2.179)). Runners in the intervention group performed strength exercises less often at other points of time during the week (other than during their warm-up routine) than runners in the control group (36.6% versus 50.0%; n=426; RR 0.790 (95%CI 0.669–0.932)). No significant results were found for using a training schedule and running technique exercises.

Conclusions The online intervention Runfitcheck was effective in stimulating aspects of injury-preventive behaviour in adult novice runners related to a warm-up routine, but did not succeed in stimulating other aspects of injury-preventive behaviour.