Health Promotion and Preventive Medicine (USACHPPM) from Fort Jackson, South Carolina. Injury data came from a prospective cohort study of six battalions of male (n = 2,945) and female (n = 2,080) Army trainees during nine weeks of the basic combat training at Fort Jackson between 1997 and 2001 (Knapik et al., 2001a; Jones, Darakjy, and Knapik, 2004). Injury data were abstracted from clinic and hospital medical records. Attrition data were taken from the same source for 2000 and from another Fort Jackson study conducted in 2001 (Knapik et al., 2004a) in order to ensure sufficient numbers and a consistent definition of attrition. Attrition was defined as failure to graduate from basic training for any reason, including preexisting medical conditions, failure to adapt to military life, serious injury during basic training, or failure to meet standards on skills. Some of these soldiers go on to repeat basic training and eventually graduate. Height and weight data were taken at the MEPS and performance on the timed run was measured at entry to basic training. Demographic characteristics of the recruits used in the injury analyses are shown in Table 4-5. Although this data source provides information only for Army recruits, comparable data for the other Services were not readily accessible.

To examine injury and attrition risk, USACHPPM initially stratified subjects by quartiles of BMI and run-time performance. Following examination of the data, they combined the middle two quartiles to improve the precision of the estimates of injury attrition risk. Table 4-6 shows the associations of successive levels of run time and BMI with injury, and