It’s a common refrain in the gym. No pain, no gain. Beneficial exercise isn’t always going to be a walk in the park — at least not for the millions of Americans who have peripheral artery disease.

This is a disease that involves a narrowing of the arteries, which restricts blood flow to the limbs. As a result, people with the condition often experience what is known as ischemic leg pain if they walk too fast. The pain can be intense, with muscle cramping in the calves, thighs or hips.

Peripheral artery disease is caused by a build-up of fat in the arteries. Risk factors include diabetes, smoking and aging. In rare cases, much younger people are susceptible.

The problem is that doctors have long recommended vigorous walks to combat the loss of mobility caused by the illness. But what if people simply slowed down to the point that they don’t suffer pain? Might they still benefit?

A recent study by University of Florida researchers looked at that idea. About 300 participants in this investigation were separated into three groups — fast walkers, slow walkers and a no-walk group. All except the last group were asked to walk 50 minutes a day, five days a week.

Findings indicated that pain appeared to be a necessary experience for a walk to do any good. In fact, those who strolled at a more leisurely, pain-free pace showed no greater improvement in mobility than a control group who didn’t walk at all.

The study didn’t identify why pain is necessary. A future investigation will analyze biopsy samples to look into biological changes in the skeletal muscles of participants.

The bottom line: Beneficial exercise isn’t always a cake walk.