By Duke Medicine News and Communications

DURHAM, N.C. -- With the warm of spring drawing many people outside for exercise, sports medicine experts at Duke University Medical Center recommend some precautions to avoid what are commonly referred to as shin splints.

Shin splints are not a specific medical condition, but rather a generic term describing pain that is experienced between the knee and ankle after physical activity.

"Although there many reasons why pain is felt in this area, shin splints are considered a cumulative stress disorder, as opposed to an acute injury," said Claude T. Moorman, III, M.D., director of sports medicine at Duke. "They typically develop when the constant pounding and stresses placed on the bones, muscles and joints overwhelm the body's natural ability to repair the damage and restore itself."

Moorman said that warming before exercise as a preventive measure for injuries such as shin splints remains hotly debated by specialists in the field.

"We at Duke, based on research at the Michael W. Krzyzewski Human Performance Laboratory (K Lab), recommend a slow warm-up period before beginning the activity," Moorman said. "We believe that about 10 minutes of graduated activity is the best way to prepare the body for exertion."

Shin splints are commonly seen in athletes, military recruits and even middle-aged weekend warriors, especially at the beginning of the season, Moorman said. Treating them can be as simple as adding extra arch support to redistribute the stresses, or changing to softer running surfaces. He also recommends "active rest," which means that a runner, for example, should take up swimming or biking for awhile, which gives the effected areas time to heal but maintains the cardiovascular benefits of exercise.

Causes of the pain that are characteristic of shin splints generally fall into two areas – muscle or bone.

The muscles that connect to the ankle are covered by a tough membrane known as fascia. This fascia holds the muscles together, but it is quite tough and inelastic. When the muscles naturally expand as a result of exertion, they have nowhere to go. This expansion cuts off circulation, and the resulting pressure causes the pain.

"This form of shin splints, known as exertional compartment syndrome, is common in athletes playing field sports like soccer or those who run a lot on hard surfaces," Moorman said.

The second major source is related to the bones, ranging from stress reactions to full-blown fractures. The constant pounding the skeleton endures during running, for example, can cause many microscopic cracks to appear on the bones of the leg. Normally, with rest, the body easily repairs these cracks. Over time, however, these tiny cracks can coalesce into a complete stress fracture, or even a complete fracture, Moorman said.