No pain, no gain is a common refrain when it comes to exercise. But that is generally referring to soreness that comes as a result of exercising, not pain while exercising. However, researchers have found that phrase takes on a new meaning for people with peripheral artery disease because if they are not experiencing pain while exercising they are not working hard enough to see benefits.
Peripheral artery disease (PAD) refers to arterial blockages that slow or stop blood flow to the legs. It is estimated to affect more than 8 million in the U.S and it makes it painful for some people to walk even short distances. The pain has been compared to angina for heart patients and there is not much in the way of treatment.
But for those who can endure the pain of a brisk walk there is hope for improvement in the condition. Researchers at Northwestern University found those who walked for exercise at an intensity that brought about ischemic leg pain from the restricted blood flow were able to improve their walking performance in terms of distance walked and length of time walked. However, those who walked at a slower pace to avoid the pain had results comparable to those who did not exercise at all.
"We've shown you have to walk to elicit ischemic leg pain to reap the benefits," said lead investigator Dr. Mary McDermott, professor of medicine at Northwestern University Feinberg School of Medicine. "It will lessen over time, and most people eventually will be able to walk further without discomfort."
A group of 300 PAD sufferers were randomly assigned to the high-intensity exercise, low-intensity exercise or control group. Both exercise groups were asked to walk 50 minutes per day five days per week. The low-intensity group was asked to walk at a comfortable pace so as to not trigger ischemic leg symptoms while the high-intensity group was asked to walk at a pace fast enough to cause ischemic leg pain. The control group consented to phone calls from study coordinators but exercise was not discussed.
Those in the high-intensity group significantly improved the distance walked in six minutes compared to the low-intensity and control groups. The high-intensity group also had significant improvement in the length of time they could walk on the treadmill.
"Patients with PAD should be advised to walk for exercise at a pace that induces ischemic leg symptoms in order to get a benefit," McDermott said. "Exercise is the most effective non-invasive therapy to improve walking in people with PAD."
While the study did not seek to identify the reasons for improvement, McDermott theorizes it can be traced to biological changes as a result of the effort. "Perhaps for people with PAD, the exercise promotes growth of new small blood vessels to their muscles," she said.