Some find walking painful

Q: To improve my health, I've started a regular walking program, but my legs get tired and feel heavy. I get painful leg cramps, too. My doctor says I don't have arthritis. What else could be going on?

A: Research shows that physical activity reduces the risk of developing heart disease, some cancers and several other illnesses. But as you've discovered, walking can be difficult for some people. Four conditions that can cause symptoms like yours are peripheral artery disease, chronic venous insufficiency, lumbar spinal stenosis and diabetic neuropathy.

1. Peripheral artery disease is a form of atherosclerosis, the condition that leads to most strokes and heart attacks. Cholesterol-filled plaques narrow arteries that carry blood to leg muscles, reducing blood flow and starving muscles of oxygen. The classic symptom is muscle cramping "downstream" from the narrowed artery. Pain can occur anywhere in the leg but occurs most often in the calf. It tends to come on with walking and go away with rest.

By itself, PAD can be serious and debilitating. But it can also signal problems elsewhere. People with PAD are six to seven times more likely to have a heart attack, stroke or mini-stroke than people without it, so controlling cardiovascular risk factors — smoking, high cholesterol and high blood pressure — is critical.

Structured exercise programs can help. These programs usually involve walking until it hurts, resting until the pain goes away and then walking again. These walk-rest-walk sessions are most effective when done for 30 minutes a day several times a week.

Your doctor may recommend low doses of aspirin to reduce your risk of heart attack and stroke. You may also benefit from medication and diet to lower blood pressure and cholesterol.

2. Chronic venous insufficiency is also caused by poor circulation, but it affects the veins. Typically, blood flows more slowly through veins than arteries. It's propelled more by contracting muscles that surround the veins than by the heart. Tiny valves inside the veins keep the blood from flowing backward.

In people with chronic venous insufficiency, the vein's valves are damaged, so blood pools in the legs and feet. Symptoms include swelling, inflammation and ulcerated, open wounds on the ankles. Legs may feel achy or heavy.

Elevating your legs so blood flows downhill to the heart can help. If you're sitting for long periods, pointing your toes up and down several times can flex the vein-pumping leg muscles. You can also try wearing compression stockings that keep blood flowing to the heart by squeezing harder at the ankle than at the knee.

3. Spinal stenosis occurs when arthritis of the spinal column, bulging disks or other problems put pressure on the spinal cord and the nerves that branch off of it. Pain stems from the pressure, and perhaps from a reduction in the blood supply that nerves need.

Lower back pain can be a symptom of spinal stenosis, especially when it occurs in the lumbar region, the section of the spine that forms the small of the back. But the legs are often affected, too. The pain can resemble that caused by PAD: cramping that increases with walking, but it's often felt in the thigh rather than the calf. The legs may also feel weak and numb. Although patients may have trouble walking, many can bike because the flexed posture reduces nerve pressure.

Treatment usually begins with physical therapy and exercises to strengthen back and abdominal muscles.

4. Diabetic neuropathy is the term for nerve damage in people with diabetes. Exactly why this happens is unclear, but high blood sugar levels may harm blood vessels that supply nerves, starving them of oxygen.

Diabetic neuropathy affects the upper and lower parts of the legs differently. In the thigh, pain can come on suddenly and in just one leg. In the lower legs and feet, where it is more common, the symptoms are typically numbness or tingling, and are usually felt in both legs. Nerve damage often dulls the ability to feel tissue damage, so sores on the feet go unnoticed and get worse. Diabetic neuropathy can make walking difficult, but symptoms may improve with exercise.

People with diabetes can reduce their chances of developing neuropathy by keeping their blood sugar down. It's less certain that tight blood sugar control is helpful once nerves have been damaged. Still, it's an important goal for other reasons. Medications can control the burning and tingling sensations.

You should be commended for adding exercise to your daily routine, but the symptoms you describe are somewhat concerning. Review your medical history with your doctor, describe your symptoms and talk about these four medical conditions. Together, you can come up with a plan to ease the pain and keep you moving.

The Harvard Medical School Adviser is researched and written by the faculty and staff of Harvard Medical School. Visit www.health. harvard.edu/adviser.