Does low aerobic performance increase musculoskeletal injury risk in the military? A systematic review with meta-analysis

Introduction: Low physical fitness has been linked with an increased risk of injury in civilian athletes and military populations, and aerobic deficits are strongly associated with an increased injury risk. Lower aerobic fitness may also be the primary determinant for military injury risk when gender differences are controlled for. This meta-analysis aimed to consolidate a large number of studies, giving statistically valid and definitive quantitative results on the association between aerobic fitness and injury risk in the military. Meta-analysis of the injury risk association between different aerobic test types, and of differences between gender outcomes from these tests in relation to injury, will be presented.

Methods: Design: Systematic review with meta-analysis. Data sources: Medline, Scopus, CINAHL and Scholar databases without date restrictions. Study selection: Primary research, in English, with objective measures of aerobic fitness and injury risk in participants from military cohorts. Data analysis: Meta-analysis comparing injury risk ratios in the lowest performance group of an aerobic test and injury risk ratios in the remaining higher performance groups. Sub-group analyses were undertaken for gender and aerobic test type.

Results: Sixteen studies were pooled for meta-analysis, representing 11 cohorts of entry-level cadets (n = 33,663) other military speciality cohorts (n = 1012). Low performance in the 1 and 2 mile, 3 km runs; VO2max test, step-test, progressive endurance run and multistage fitness test was associated with a statistically significant higher injury risk. Low performance in continuous running tests was associated with increased injury risk, with a Risk Ratio (RR) of 1.53 [95% CI, 1.25–1.87], as were incremental aerobic tests, RR 1.93 [95% CI, 1.44–2.60]. In continuous running tests, the lowest performing men had a pooled injury risk of RR 1.39 [95%CI, 1.16–1.67]. The injury risk for females in the lowest continuous running test performance groups was RR 1.65 [95% CI, 1.29–2.10].

Conclusion: Low aerobic fitness is significantly associated with increased military injury risk, and it appears that the type of test used does not change this predictive value. This association is demonstrated in both male and female personnel. Future research can test the effect of improving aerobic fitness on military injury incidence, as this study demonstrates that aerobic fitness is significantly associated with increased injury risk in the military. Currently it is not known whether a lack of aerobic fitness is causative, or purely indicative of an association with other causative characteristics.