Your bones are constantly remodeled throughout your life. This process helps to keep them strong and to maintain their integrity for withstanding stresses, and maintaining homeostasis. In a healthy adult the rate of resorption roughly equals the rate of bone deposition..  In older people the rate of deposition often falls below that of resorption and osteoporosis results. Bone remodeling is stimulated by physical stress placed on the bone by exercise, and will be tailored to provide specific adaptation to that stress. In that way a weight lifter's bones will show growth patterns peculiar to the stresses placed on the bones.