In people with peripheral artery disease, walking to exercise intensity that causes ischemic pain in the legs (caused by limited blood flow) improves walking performance, new research suggests. The findings of the study were published in a journal called “JAMA”.
The study also showed that walking at a slow pace that does not cause ischemic leg symptoms is no more effective than no exercise at all. This randomized trial is the first to show that an indoor walking exercise program improved walking ability in people with peripheral artery disease when the exercise was performed at high intensity that induced ischemic leg symptoms, but not when the exercise was performed at low intensity without ischemic leg symptoms. . “We have shown that you have to walk to cause ischemic pain in your legs in order to pick the fruit,” said the leading investigator, Dr. Mary McDermott, professor of medicine at Northwestern Feinberg University School of Medicine.
McDermott added, “It will shrink over time, and most people will eventually be able to walk on without discomfort.” Previous McDermott research has suggested that pain during exercise prevents many people with PAD from walking.
Although the study did not identify biological changes that lead to improved gait, McDermott said that previous research shows that intense exercise stimulates certain biological pathways that promote improved mitochondrial activity, a chemical source of cellular energy. “Perhaps for people with PAD, exercise promotes the growth of new small blood vessels in their muscles,” McDermott said.
About 8.5 million people in the United States and about 250 million people worldwide have peripheral artery disease of the lower extremities (PAD). People with PAD have blockages in the arteries that slow down or stop the flow of blood to the legs. As a result, they have pain and difficulty walking even over short distances. It is comparable to angina for people who have symptomatic heart disease. There are several therapies to treat it. The first month consisted of weekly personal visits to the coach. These sessions helped participants learn the difference between high- and low-intensity walking, enabled them to learn to use the technology used to track the intensity of their exercise at home, and helped them begin their exercise activities. The program then consisted of phone calls and remote monitoring by trainers.
Remote monitoring is important, McDermott said. Although supervised exercise is covered by Medicare and other insurance companies, most people with PAD do not participate in supervised exercise because of the burden associated with traveling three times a week to a medical center to participate. For the study, 305 people with peripheral artery disease at four medical centers were randomized to high-intensity exercise, low-intensity exercise, or a control group that received non-exercise-related phone calls.
Those who were randomly selected for an exercise were asked to walk for up to 50 minutes per session, five days a week. Those of high intensity were asked to walk at a pace that was fast enough to cause ischemic leg symptoms during exercise. Those who were randomly selected for low intensity were required to walk at a comfortable pace that did not cause ischemic leg symptoms. Intensity was monitored remotely using ActiGraph activity monitors worn by participants during exercise. This data was transferred to the study website and reviewed by the study trainer. The six-minute walk, treadmill testing, and outcomes reported by patients were measured at baseline and during the 12-month follow-up.
Patients who participated in the high-intensity walking exercises significantly improved the distance they could walk in six minutes compared to the low-intensity group or the control group. The high-intensity exercise group also significantly improved the length of time they were able to walk on the treadmill at the end of the study, compared with both other groups. “Patients with PAD should be advised to walk to exercise at a pace that causes ischemic leg symptoms to benefit,” McDermott said.
McDermott further remarked, “Exercise is the most effective noninvasive therapy to improve walking in people with PAD.” The next step in the research is to establish a biological explanation for the finding that lower extremity ischemia appears to be necessary to achieve the benefits of walking exercise in people with PAD.