The relationship between low aerobic fitness and injury in the military

Introduction: Injury in the military can be experienced in up to 25% of men and 50% of women. This poses a significant threat to a soldier's health and readiness for deployment, and accounts for significant expenditure of money and resources. The physical fitness of military personnel is regularly measured with aerobic running tests despite the fact that higher running distances in training increases the risk of musculoskeletal injury. Methods: A systematic review of the literature was conducted by searching Cinahl, Scopus and Medline (via Web of Science) databases for primary research that analysed the relationship between injury incidence and physical fitness tests in any military population. Results: Twenty-two studies were included that assessed the relationship between physical fitness and injury in the military. All but one of these studies assessed the links between aerobic fitness testing and injury with running measures, 2 of which identified progressive running test formats and another 2 papers studied non-running aerobic fitness tests. The papers that analysed running tests (from 1.6 km to 3.2 km) found significant (p = 0.03–0.05) risk ratios for injury between 1.43 and 2.8 for those who were in the slowest quartile of run times. The progressive endurance runs showed significant (p = 0.000) risk ratios between 2.2 and 2.58 in poorly performing groups, while those who failed non-running aerobic tests were up to 1.31 times more likely to experience an injury (95% CI = 1.20–1.44). Discussion: Running tests are an estimate of maximal aerobic capacity and the results of this review suggest that low aerobic fitness, irrespective of the test type, is a risk factor for injury in the military. Running may have value for lower limb conditioning for military specificity, but the significance in terms of injury prevention appears to relate to improving aerobic fitness. If increasing aerobic fitness and decreasing soldiers’ running mileage reduces the risk of injury, then the current practice of high-load running training should be reconsidered. A more varied aerobic training program could be implemented to mitigate these risk factors. A future randomised control trial would be effective to test the benefits of non-running aerobic conditioning to meet the requirements for physical conditioning in the military, while reducing the risk of injury