MINNEAPOLIS — Simple calf muscle stretching may reduce leg pain when walking and increase blood flow for people with peripheral artery disease, preliminary data suggest.

In a study presented Friday at the American Heart Association’s Arteriosclerosis, Thrombosis and Vascular Biology/Peripheral Vascular Disease 2017 Scientific Sessions, participants who stretched daily for a month improved the ability of their calf arteries to relax and expand to let blood flow through after being momentarily held back with a blood pressure cuff, from an average 3.7 percent to 5.2 percent.

“This is a very safe, easy intervention that can be done at home and has the potential to really improve your tolerance for walking and get you into a walking program,” said Judy M. Muller-Delp, Ph.D., the study’s senior researcher and professor of biomedical sciences at the Florida State University College of Medicine in Tallahassee.

Peripheral artery disease affects more than 8.5 million American adults and many are unaware they have it. The most common symptom in the lower extremities is a painful muscle cramping in the hips, thighs or calves when walking, climbing stairs or exercising. The pain of PAD often goes away within a few minutes after exercise is stopped.

If blood flow is blocked due to plaque buildup, the muscles don’t get enough blood during exercise to meet the needs. The “crampy” pain, called intermittent claudication, is the muscles warning the body that it isn’t receiving enough blood during exercise to meet the increased demand.

In the study, researchers evaluated 13 patients, most taking a statin drug and antiplatelet medications. Participants were instructed to passively stretch their calf muscle in 30-minute daily sessions using a splint that flexed the ankle about 15 percent. Walking ability and blood flow were measured after four weeks of calf stretching of each leg five days a week and after four weeks without the special stretches.

After one month of daily calf stretches, participants also extended how far they could walk in six minutes — about half a city block farther, but still well below normal for people the same age. They also prolonged the distance they could walk before needing to stop and rest due to leg discomfort.

Structured walking programs are a cornerstone of PAD treatment, along with medication and sometimes interventions to open clogged blood vessels.

“A physical therapist can instruct you how to adjust and wear the splints correctly so you can do the stretches at home,” said the study’s lead researcher Kazuki Hotta, Ph.D., a postdoctoral fellow in engineering science at the University of Electro-Communications in Tokyo. “There is no doubt about the benefit of exercise training on blood vessel health in PAD patients.”