The muscles and tendons that cover the shin bone become inflamed and may cause swelling. In extreme cases you feel pain before, during, and after exercise. It is caused by repetitive pounding of your feet during running sports like aerobics, basketball, and volleyball. Stress fractures appear as tiny cracks in the lower leg bones. They may occur when muscle tolerance is exceeded, or when muscle contractions bend the bones.
Stress fractures are common in distance runners and ballet dancers.
If you have thin bones, you are at a greater risk as well. The muscles in the lower leg are in compartments separated by membrane walls. Excessive training can cause muscles to get too big for their compartments. When the leg is at rest there is no problem. During exercise the muscles swell with blood, putting pressure on the nerves and blood supply.