Risk Factors for Stress Fracture Injury in British Army Junior Entry Recruits

Abstract

Stress fracture injury is commonly reported in military recruits during initial training. Junior Entrants (JE, aged 16–17 years) undertake different training courses to those entering standard Phase-1 training. The potential risks for stress fracture injury may therefore be different in JE. PURPOSE: The aim of this study was to identify the risk factors for stress fracture injury in JE recruits. METHODS: Demographic, physical performance and lifestyle factors, and injury data were obtained retrospectively for recruits entering British Army training between January 2002 and August 2005. The filtered dataset contained 1035 records for JE undertaking either a 20–24 week course at Army Training Regiment (Bassingbourn; (ATR B)), or a 42 week course at the Army Foundation College, Harrogate. The relative risk (RR, (95% confidence intervals)) of injury for each factor was tested for statistical significance using Chi-squared contingency analysis. RESULTS: There were a total of 55 (5.3%) recorded stress fracture cases at the training establishments, with a higher rate of stress fractures at ATR B (Obs χ21 = 21.2, p < 0.001). Females were eight times more likely to sustain a stress fracture injury than males (Obs ?21= 81.8, p< 0.001). Males who completed the 1.5-mile run in a time slower than the mean were three times more likely to suffer a stress fracture (RR, 3.09 (1.76-4.42); p< 0.01). A lower General Trainability Index was also a significant risk factor for stress fracture injury in males (RR, 0.49 (0.00 - 1.00); p < 0.05). Alcohol consumption (RR, 2.10 (0.83 - 3.37); p < 0.05) and oral contraceptive pill use (RR, 6.85 (3.32 - 10.38); p < 0.01) were the only significant risk factors for stress fracture injury in female JE. All other demographic, performance and lifestyle factors were not significant for stress fracture injury in either males or females. CONCLUSIONS: The incidence rate of stress fracture injury in JE is comparable with data reported elsewhere for Standard Entrants. Whereas the main risks for stress fracture injury in male JE were related to physical performance, predictive factors in female JE were related to lifestyle. These risk factors are modifiable and should be considered in future preventative strategies.