Background: Stress fracture are bone injuries due to overuse, which depleting bone tissue and causing tissue discontinuity. The incidence of these injuries is common in the military population and accounts for 31% of injuries to new military members. Intrinsic risk factors for stress fractures include low bone density, body composition, muscle weakness, and physical fitness while extrinsic risk factors including surface type used for exercise, calorie reduction, and sudden change in volume of physical activity. These risk factors can be reduced by regular physical activity and adequate rest periods, as the bones become stronger in conjunction to muscle strength. Method: This study is an observational analytical study with a case control design using a retrospective approach. This study population is new students of Sekolah Polisi Negara (SPN) Selopamioro Yogyakarta, and samples were taken according to inclusion and exclusion criteria. Results: The results showed that there was an effect in BMI for reducing stress fracture risk with p value=0,347 and OR 4 (95% CI 0,56-28,39). There was also an effect in pre basic military training exercise in reducing stress fracture risk with p value=0,637 and OR 2,5 (95% CI 0,37-16,88). Conclusions: There was an effect in BMI and pre basic military training exercise in stress fracture incidence.