Epidemiology of stress fracture and lower-extremity overuse injury in female recruits

Purpose: The purpose of this prospective study was to examine rates and risk factors for overuse injuries among 824 women during Marine Corps Recruit Depot basic training at Parris Island, SC, in 1999. Methods: Data collected included training day exposures (TDE), baseline performance on a standardized 1.5-mile timed run, and a pretraining questionnaire highlighting exercise and health habits. The women were followed during training for occurrence of stress fracture and other lower-extremity overuse injury. Results: There were 868 lower-extremity overuse injuries for an overall injury rate of 12.6/1000 TDE. Rates for initial and subsequent injury were 8.7/1000 and 20.7/1000 TDE, respectively. There were 66 confirmed lower-extremity stress fractures among 56 (6.8%) women (1.0/1000 TDE). Logistic regression modeling indicated that low aerobic fitness (a slower time on the timed run (> 14.4 min)), no menses in six or more consecutive months during the past year, and less than 7 months of lower-extremity weight training were significantly associated with stress fracture incidence. Self-rated fair-poor fitness at baseline was the only variable significantly associated with other non-stress fracture overuse injury during basic training. Conclusions: Among this sample of women, the risk of lower-extremity overuse injury was high, with a twofold risk of subsequent injury. The results suggest that stress fracture injury might be decreased if women entered training with high aerobic fitness and participated frequently in lower-extremity strength training. Furthermore, women reporting a history of menstrual irregularity at their initial medical exam may require closer observation during basic training.