here's an article from a medical textbook
Shin Splints
A shin splint is pain resulting from damage to the muscles along the shin.
The usual cause is long-standing, repeated stress to the lower leg. Two groups of muscles in the shin are susceptible to shin splints. The location of the pain depends on which group is affected.
Anterolateral shin splints affect the muscles in the front (anterior) and outside (lateral) parts of the shin. This type of injury results from a natural imbalance in the size of opposing muscles. The shin muscles pull the foot up, and the larger and stronger calf muscles pull the foot down each time the heel touches the ground during walking or running. The calf muscles exert so much force that they can injure the shin muscles.
The main symptom of anterolateral shin splints is pain along the front and outside of the shin. At first, the pain is felt only immediately after the heel strikes the ground during running. If running is continued, the pain occurs throughout each step, eventually becoming constant. Usually by the time the person sees a doctor, the shin hurts when touched.
To allow this type of shin splint to heal, the runner must stop running temporarily and do other kinds of exercise. Exercises to stretch the calf muscles are helpful. Once the shin muscles start to heal, exercises to strengthen them, such as the bucket-handle exercise, can be done in 3 sets of 10 every other day.
Posteromedial shin splints affect the muscles in the back (posterior) and inner (medial) parts of the shin, which are responsible for lifting the heel just before the toes push off. This type of shin splint often results from running on banked tracks or crowned roads and can be worsened by rolling the feet inward excessively or by wearing running shoes that don't adequately prevent such rolling.
Strengthening the Shin Muscles
Bucket-handle exercise
Wrap a towel around the handle of an empty water bucket. Sit on a table or other surface high enough to prevent the feet from touching the floor. Place the bucket handle over the front part of one shoe. Slowly raise the front of the foot by flexing the ankle, then slowly extend the foot by pointing the toe. Repeat 10 times, then rest for a few seconds. Do 2 more sets of 10. To increase resistance, add water to the bucket--but not so much that the exercise is painful.
Toe raises
Stand up. Slowly rise up on the toes, then slowly lower the heels to the floor. Repeat 10 times, then rest for 1 minute. Do 2 more sets of 10. When this exercise becomes easy, do it while holding progressively heavier weights.
Outward rolls
Stand up. Slowly roll the ankle out so that the inner part of the sole is raised off the floor. Slowly lower the sole back to the floor. Do 3 sets of 10.
The pain produced by this type of shin splint usually starts along the inside of the lower leg, about 1 to 8 inches above the ankle, and worsens when a runner rises up on the toes or rolls the ankle in. If the person continues to run, the pain moves forward, affecting the inner ankle, and may extend up the shin to within 2 to 4 inches of the knee. The severity of the pain increases as the shin splints progress. At first, only the muscle tendons are inflamed and painful, but if the person persists in running, the muscles themselves can be affected. Eventually, tension on the inflamed tendon can actually pull it from its attachment to bone, causing bleeding and further inflammation. Sometimes the part of the shinbone attached to the tendon is torn away.
The primary treatment is to stop running and do other types of exercise until running is no longer painful. Running shoes with a rigid heel counter (the back part of the shoe) and special arch supports can keep the foot from rolling in excessively. Avoiding running on banked surfaces can help prevent shin splints from recurring. Exercises to strengthen the injured muscles are useful. For severe cases in which a part of the shinbone has been torn away, treatment may include surgery to reattach it. Afterward, the person must not run for a long time. An experimental treatment consisting of calcitonin (a hormone that builds bone) injected daily or alendronate (a drug that slows bone loss) given by mouth has healed some shin splints that were unresponsive to other measures. Sometimes none of the available treatments are effective, and the runner must abandon running permanently.