Running to breaking point? The relationship between 1.5-mile run time and injury risk in female recruits during British Army basic training

Introduction The 1.5-mile best-effort run is used in the British Army to assess the fitness of all recruits and trained service personnel by means of the physical fitness assessment (PFA). The 1.5-mile run is a basic measure of fitness and slower times have been associated with an increased risk of musculoskeletal injury (MSkI), particularly during this early stage of training. The aim of this study was to establish whether 1.5-mile run times were associated with subsequent MSkIs among female recruits during their 14-week basic training. Method Retrospective data were analysed from female recruits who had undertaken basic military training between June 2016 and October 2017. This included retrieving the results of their week 1 PFA; recording the type, cause and week of MSkI if they had sustained one; and noting down their outcome from basic training. Run times were statistically analysed in relation to MSkI occurrence of 227 female recruits using binomial logistic regression with an accepted alpha level of p value <0.05. Results 1.5-mile run time predicted risk of MSkI (chi(2) (1)=12.91, p<0.0005) in female recruits. The mean run time for injury-free recruits was faster than for injured recruits (12 min 13 s compared with 12 min 43 s). Every 10 s increase in run time was associated with an 8.3% increase in risk of injury. Conclusion Slower 1.5-mile best-effort run time, as a surrogate of aerobic fitness, is associated with increased risk of MSkI in female recruits during basic training.