Background Increased physical activity is often recommended for weight maintenance and loss. Therefore many overweight persons want to take up running as a form of exercise. Although running has positive effects on health and fitness, the incidence of a running related injury (RRI) is high.

Objective To examine the risk of sustaining a RRI in overweight novice runners.

Design prospective cohort design.

Setting Novice runners (N=848) preparing for a recreational 4-mile (6.7-km) running event.

Participants Participants were recruited by local newspapers. 334 novice runners with a Body mass index (BMI) of 25 or more and 514 novice runners with a BMI less than 25 started with a beginners training program.

Assessment of risk factors After completing a baseline questionnaire and orthopaedic examination all novice runners registered information on running characteristics and RRI using an Internet-based running log.

Main outcome measurement The primary outcome measure was RRIs per 100 participants. An RRI was defined as any musculoskeletal complaint of the lower extremity or back causing a restriction of running for at least 1 week. Secondary outcome measure was exposure time during follow-up.

Results 25% (82 of 334) of the overweight novice runners sustained a RRI during follow-up compared to 15% (76 of 514) in the group of participants with BMI<25. The difference in proportion was significant (χ²=4.77, df=1, p=0.03). Furthermore, the mean exposure time in both groups was equal, that is, 346 versus 349 min in the overweight group.

Conclusion Overweight novice runners that take up running are more prone to a RRI. Although the proportion of injured runners in the overweight group was significantly higher, the exposure time was equal in both groups.