The etiology of running-related injury is important to consider as the effectiveness of a given running-related injury prevention intervention is dependent on whether etiologic factors are readily modifiable and consistent with a biologically plausible causal mechanism. Therefore, the purpose of the present article was to present an evidence-informed conceptual framework outlining the multifactorial nature of running-related injury etiology. In the framework, four mutually exclusive parts are presented: (a) Structure-specific capacity when entering a running session; (b) structure-specific cumulative load per running session; (c) reduction in the structure-specific capacity during a running session; and (d) exceeding the structure-specific capacity. The framework can then be used to inform the design of future running-related injury prevention studies, including the formation of research questions and hypotheses, as well as the monitoring of participation-related and non-participation-related exposures. In addition, future research applications should focus on addressing how changes in one or more exposures influence the risk of running-related injury. This necessitates the investigation of how different factors affect the structure-specific load and/or the load capacity, and the dose-response relationship between running participation and injury risk. Ultimately, this direction allows researchers to move beyond traditional risk factor identification to produce research findings that are not only reliably reported in terms of the observed cause-effect association, but also translatable in practice.

Background/Purpose: High body mass index is associated with an increased risk of running-related injury among novice runners. However, the amount of running participation plays a fundamental explanatory role in regards to running-related injury development. Therefore, the purpose of the present study was to investigate if the risk of running-related injury among obese novice runners (BMI 30-35) was different when the start-to-run distance was 3km per week instead of 6km per week. Hypothesis:A start-to-run distance of 3km per week is associated with 20% fewer running-related injuries and significantly fewer symptoms of overuse injury than a start-to-run distance of 6km per week among obese novice runners. Study design: Randomized trialMethods: Fifty-six obese novice runners with a body mass index between 30-35 were enrolled and randomized to receive one of the two following Interventions: (i) a 4-week running program with a start-to-run distance of 3km per week including three sessions with 1km running per session (n=29), or (ii) a 4-week running program with a startto-run distance of 6km per week including three sessions with 2km running per session (reference group, n=27). In both programs, the weekly running distance was increased by 10% each week throughout the follow-up. Results:The intention-to-treat analysis revealed a protective cumulative risk difference of -16.3% (95%CI: -43.8%; 11.3%, p=0.25) after four weeks. Importantly, some participants completed much more running than prescribed (n=5) and some never uploaded any training (n=15). Therefore, a supplementary per-protocol analysis was performed revealing a cumulative risk difference of -31.2% (95%CI: -57.0%; -5.2%, p=0.02) after four weeks. Furthermore, in the per-protocol analysis, the cumulative risk difference of overuse-injury symptoms was -47.8% (95%CI: -81.0%; -14.6%, p=0.01) after four weeks of running Conclusions: A 3km reduction from 6km per week to 3km per week in the start-to-run distance appears to be associated with fewer running-related injuries and significantly fewer symptoms of overuse injury.