Background Novice runners have a high injury risk. The online behavioral intervention Runfitcheck was effective in stimulating preventive behavior in novice runners, but its effectiveness on running-related injuries (RRI) remains unknown.

Objective To evaluate the effectiveness of the Runfitcheck on RRIs among adult novice runners.

Design A three-arm randomized controlled trial was conducted over a period of seven months.

Setting Competitive level: novice runners.

Participants A total of 851 participants of 18 years or older, considering themselves as inexperienced, slightly or rather experienced runners or having less than one year running experience, were eligible. From those, 741 participants completed at least one of the health monitors and were included in the analysis.

Intervention The Runfitcheck is an online intervention to stimulate injury-preventive behavior. The participants were allocated to one of two intervention groups or the control group. One intervention group obtained access to the Runfitcheck and was fortnightly stimulated to use Runfitcheck, the other intervention group was attended to the Runfitcheck once. Participants were followed over a period of four months.

Main outcome measures The main outcome measure was a new RRI, measured fortnightly with the Oslo Sport Trauma Research Centre overuse injury questionnaire.

Results The time to the occurrence of the first RRI did not differ between the study groups (Wald Chi-square 0.893). There was also no difference in risk of a new RRI in the group attended to the Runfitcheck once (OR 1.22 (95%CI:0.86–1.74)) nor in the active approach group (OR 1.01 (95%CI: 0.71–1.45)) compared to the control group. Furthermore, the onset of the new RRIs did not change over time (OR 0.96 (95%CI: 0.91–1.01)).

Conclusions The online intervention Runfitcheck was not effective in reducing the risk of new RRIs in adult novice runners. More research is needed to determine how injuries in novice runners can be prevented.