Cox proportional hazards regressions will be used to compute the hazard rates (HR) in the exposure groups, using first-time injury as the primary outcome. Date of inclusion (baseline evaluation date) and date of injury or of censoring will be basic data used to calculate the time at risk, which is expressed in hours spent running and defined as the time-scale. A participant will be right-censored if injury unrelated to running or severe disease caused a modification of the running plan, or at the end of follow-up. The assumption of proportional hazards will be evaluated by log-minus-log plots.