Exercising on a treadmill can improve the health and mobility of stroke victims decades after the damaging event.

Researchers at Johns Hopkins University recruited over 70 patients who, on average, suffered a stroke four years before the study.

They underwent physical exams and brain scans -- half were assigned to a treadmill exercise program, the other half performed stretching exercises.

They found those in the treadmill group had improved athletic ability, were more fit, and had increased activity in their brainstem.

Experts say this simple exercise may be able to "retrain" the brain -- even if it's been a long time since the stroke occurred.

In other medical news…

Assessing a heart transplant patient's risk for organ rejection just got easier.

The FDA approved a new test, called Allomap, which measures genetic information in a patient's white blood cells.

The test then assigns a score indicating whether the body appears to be rejecting the new organ.

White blood cells are involved in the immune system and help the body fight infection.

The test costs about three thousand dollars.