A stress fracture of the pars interarticularis is usually a result from an overuse injury. In activities that require excessive arching or rotation of the lower back, the rear portion of the vertebral bones are overstressed. In response to this increased stress, the bone increases its bone turnover. Bone turnover involves the removal of weakened, damaged areas of bone and the laying down of new bone at the same location. To do this, old bone is resorbed (removed) before it is replaced with new bone. If bone formation cannot keep up with bone resorption, areas of weakness can develop within the bone. These can develop into a stress fracture if the bone is continually loaded. This is commonly seen in activities such as gymnastics, fast bowling in cricket, tennis, rowing, dance, weightlifting, pole vaulting and any throwing activities such as baseball pitching, javelin, discus and hammer throw.