risk because their bones have yet to reach full density and strength. The female athlete triad also can put women at risk as disordered eating and osteoporosis can cause the bones to be severely weakened. This type of injury is mostly seen in lower extremities, due to the constant weight-bearing (WB). The bones commonly affected by stress fractures are the tibia, tarsals, metatarsals (MT), fibula, femur, pelvis and spine. Upper extremity stress fractures do occur, but they are uncommon. When stress fractures occur in the upper extremity its commonly in the upper torso and is caused by muscle forces. The population that has the highest risk for stress fractures is athletes and military recruits who are participating in repetitive, high intensity training. Sports and activities that have excessive, repetitive ground reaction forces have the highest incidence of stress fractures. The site at which the stress fracture occurs depends on the activity/sports that the individual participates in. Women are more at risk for stress fractures than men due to factors such as lower aerobic capacity, reduced muscle mass, lower bone mineral density, among other anatomical and hormone-related elements. Women also have a two- to four-times increased risk of stress fractures when they have amenorrhea compared to women who are eumenorrheic. Reduced bone health increases the risk of stress fractures and studies have shown an inverse relationship between bone mineral density and stress fracture occurrences. This condition is most notable and commonly seen on the femoral neck. Other animals Dinosaurs In 2001, Bruce Rothschild and other paleontologists published a study examining evidence for stress fractures in theropod dinosaurs and analyzed the implications such injuries would have for reconstructing their behavior. Since stress fractures are due to repeated events they are probably caused by expressions of regular behavior rather than chance trauma. The researchers paid special attention to evidence of injuries to the hand since dinosaurs' hind feet would be more prone to injuries received while running or migrating. Hand injuries, meanwhile, were more likely to be caused by struggling prey. Stress fractures in dinosaur bones can be identified by looking for bulges on the shafts of bones that face toward the front of the animal. When X-rayed, these bulges often show lines of clear space where the X-rays have a harder time traveling through the bone. Rothschild and the other researchers noted that this "zone of attenuation" seen under the X-ray typically