Duty Factor And The Incidence Of Running Related Injuries: A 1-year Prospective Cohort Study

Running as a regular physical activity contributes, in a cost-effective and preventive manner, to a healthy lifestyle. However, 25-75 % of all runners annually sustain a running-related injury (RRI). The aim of previous studies in the literature was to determine running style by a specific parameter (e.g., footstrike pattern), which contradicts the multifactorial nature of running-related injuries (RRI). PURPOSE: To investigate the associations between RRI incidence and the duty factor (DF) during running. METHODS: A sample of 678 participants was divided into three groups (Low (LDF), Medium (MDF), and High (HDF)) based on their DF normalized by speed. The inclusion criteria included the completion of a VO2max test during a baseline measurement and a weekly running volume of 6 km at a minimum. The RRI data were derived from weekly injury self-reporting via a mobile app during a 1-year follow-up after baseline measurement (Acute RRI (AC), Overall RRI (OL)). DF was derived from overground running trials as the ratio of the stance time and flight time. Binary logistic regression was used to determine the relationship between injury incidence and the DF group. The alpha level was set at P ≤ 0.05. RESULTS: There were 187 OL and 105 AC (OL/AC: LDF(65/34); MDF(52/28); HDF(70/43)). The logistic regression model for OL was significant (x2(6) = 33.5, P < 0.01) indicating that MDF had significantly lower odds of having AC compared to HDF (95% CI, 0.387-0.926; P = 0.021), model for the AC ((x2(6) = 13.9, P = 0.03) indicated the same trend for MDF (95% CI, 0.344-0.991; P = 0.046). Both models were controlled for age, weight, and training volume. CONCLUSIONS: The findings from binary logistic regression suggest that maintaining a medium DF (0.14 - 0.19) appears protective against having AC or OL. European Union and Ministry of Education, Youth and Sports of the Czech Republic, grant number CZ.02.1.01/0.0/0.0/16_019/0000798 Program 4 Healthy Aging in Industrial Environment, European Union under the LERCO project number CZ.10.03.01/00/22_003/0000003 via the Operational Program Just Transition