Association Between Running Characteristics and Lower Extremity Musculoskeletal Injuries in United States Military Academy Cadets

Background: Running-related overuse injuries are common among recreational runners; however, there is currently little prospective research investigating the role of running characteristics on overuse injury development. Purpose: To investigate the relationship between running characteristics and lower extremity musculoskeletal injury (MSKI). Study Design: Cohort study; Level of evidence, 2. Methods: The study included 827 incoming cadets of the class of 2020 at the United States Military Academy. Before cadet basic training, running spatiotemporal parameters (stride length, ground contact time, and cadence) were recorded for each participant, and foot-strike pattern was analyzed. Demographic data were recorded and analyzed as potential covariates. Lower extremity MSKIs sustained over the 9 weeks of cadet basic training were documented. Kaplan-Meier survival curves were estimated, with time to incident lower extremity MSKI as the primary outcome, by level of the independent predictor variables. Risk factors or potential covariates were carried forward into multivariate Cox proportional hazards regression models. Results: Approximately 18.1% of participants incurred a lower extremity MSKI resulting in >= 3 days of activity limitation during cadet basic training. Univariate analysis indicated that participants with the shortest stride length (<133.0 cm) were 39% more likely to incur any lower extremity MSKI and 45% more likely to incur an overuse MSKI than those with the longest stride length (>158.5 cm), and that participants with the longest ground contact time (>0.42 seconds) were twice as likely to incur any MSKI than those with the shortest contact time (<0.28 seconds). After adjusting for sex, weekly distance running 3 months before cadet basic training, and history of injury, multivariate regression analysis indicated that participants with the longest contact times were significantly more likely to incur overuse lower extremity MSKI than those with the shortest contact times (hazard ratio, 2.15; 95% CI, 1.06-4.37). There was no significant difference in risk of MSKI associated with foot-strike pattern or cadence. Conclusion: Study participants running with the longest ground contact times were 2.15 times more likely to incur an overuse lower extremity MSKI during cadet basic training than those with the shortest contact times. Also, study participants with the shortest stride length were 45% more likely to incur an overuse MSKI than those with the longest stride length.