Doctors have recommended exercise as therapy for individuals suffering from peripheral artery disease (PAD) for years, and now a new study explains why it’s so beneficial.

Researchers at Beth Israel Deaconess Medical Center have found that a protein called PGC-1alpha plays a key role in the process known as angiogenesis, which spurs the growth of new blood vessels.

The research team studied the effect of exercise on mice for their results. As expected, the animals that exercised were found to have high levels of angiogenesis. They also found the mice that were lacking the PGC-1alpha protein failed to grow new blood vessels in response to exercise. Ultimately, their experiments demonstrated that exercise activates beta-adrenergic signaling, which leads to a robust induction of PGC-1alpha.

The findings suggest, according to researchers, that walking daily is the best therapy for PAD sufferers.

PAD affects 5 million individuals in the U.S. and is the leading cause of limb amputations. It is a common circulatory problem in which narrowed arteries reduce blood flow to the limbs. It is characterized by leg pain primarily encountered while walking, but can also be a sign of widespread accumulation of fatty deposits in the arteries.

Besides exercise, lowering cholesterol and quitting smoking are among the ways to reduce the progression of PAD, according to the Mayo Clinic.

Nutritional supplements containing gingko are also believed to help manage the discomfort associated with the disease.