DEAR DR. DONOHUE: We are a group of elderly people who are very health-conscious and would like to improve our breathing to enable us to walk or jog farther. Are there any exercises that improve lung capacity? We would like to do some without investing in equipment or membership in a gym. – A.B.

ANSWER: No exercise strengthens the lungs themselves. Lungs don’t respond to exercise like muscles do. However, exercise greatly improves lung function. If that sounds contradictory, it isn’t.

Exercise improves the function and strength of breathing muscles. The diaphragm – the horizontal sheet of muscle that lies between the abdomen and the chest – is the most important breathing muscle. When it drops downward, air rushes into the lungs. A healthy diaphragm descends lower, recovers more quickly and pulls in more air than an untrained diaphragm. You can focus on diaphragm breathing by putting your hand on your stomach. When you take a breath in, your hand should be pushed outward. The more you make a habit of diaphragmatic breathing, the more air you’ll bring into your body.

Exercise teaches muscles and organs how to extract more oxygen from blood as it passes through them. That is something that doesn’t come from anything you consciously do, but it comes as a freebie from regular exercise.

Exercise improves the pumping ability of the heart. That, in turn, delivers more blood and more oxygen to muscles, and it enables people to do more and more physical activity without become breathless.

You don’t need any special equipment, and you don’t need a gym. You need a pair of comfortable shoes. Start with a modest walking program. If you can manage only half a block, that’s enough. Every three days, increase the distance walked and the pace at which you walk it. The goal is 30 minutes of continuous walking at a pace that’s brisk but not so taxing that you can’t carry on a conversation. You can even break those 30 minutes into two 15-minute or three 10-minute sessions.

At older ages, the start of any exercise program should be in the doctor’s office for a clearance to exercise.

DEAR DR. DONOHUE: I am a 27-year-old woman who runs three or four times a week for 3 to 6 miles each run. I also lift weights and run stairs. I have begun to notice pain in my left foot. X-rays of the foot are normal. The pain was diagnosed as a stress fracture, and I was advised to take six weeks off. How long after healing can one expect to have pain? What other conditions could cause it? – R.B.

ANSWER: Stress fractures are tiny cracks in a bone. They often occur when a person increases mileage or runs on a different surface. They’re the same kind of cracks that occur in steel beams when they are pushed beyond the limits of their innate structural strength.

It takes three or four weeks for stress fractures to show on an X-ray, but a bone scan detects them a number of days after they occur. Even without scans, the diagnosis can be pretty certain from physical signs. The area of the fracture is quite tender to finger pressure. A vibrating tuning fork placed on the suspected site elicits pain.

These fractures heal within three to eight weeks. Four to six weeks of rest is generally considered sufficient. A person should not resume running until there has been no pain for two weeks with the foot supporting body weight. Resumption of training should begin with a reduced volume of exercise.

Other conditions that cause similar pain include inflammation of the joints at the base of the toes, a disruption of blood supply to the involved bone (avascular necrosis), and a neuroma, a growth of scar-like tissue that enmeshes a foot nerve and compresses it.

If your symptoms haven’t lessened considerably with four weeks of rest, you need an orthopedic doctor’s opinion.

DEAR DR. DONOHUE: I am 78 and have a treadmill with a belt that turns. You walk on it. I have no faith that I can lose weight by walking on it. Can I? – D.T.

ANSWER: Sure, you can. You burn lots of calories from walking on a treadmill. Why wouldn’t you?

DEAR DR. DONOHUE: Please say something about TIA. My doctor tells me I had one. He’s not making a big deal about it. Does that mean I shouldn’t make a big deal about it either? – J.O.

ANSWER: A TIA – transient ischemic attack – is a big deal, and doctors and patients should make a big deal about one. It’s an interruption of blood flow (“ischemic” – is-KEY-mick) to the brain that lasts minutes to hours but never longer than one day (“transient”). The usual duration is an hour or so.

Symptoms depend on which part of the brain is deprived of blood. Sometimes people find themselves unable to talk; have visual problems, including partial or total loss of sight in one eye; become weak in an arm or leg; experience numbness of the face or an extremity; or stagger when they try to walk.

The fact that these defects last only a relatively short time is a relief, but it doesn’t diminish the importance of what happened. Close to 10 percent of those who have a TIA go on to have a full stroke within 90 days. Respect a TIA as a warning of future trouble unless something is done to prevent it.

There’s real urgency to find out where the blood-flow interruption took place and why it took place. Many times, there is a blockage in one of the carotid arteries in the neck. Those arteries are the brain’s main blood-flow conduits. Blockages in the carotid arteries can often be surgically removed. The procedure is called an endarterectomy. More and more experience is being gained at squashing carotid-artery buildup with a balloon, a procedure similar to one used for blocked heart arteries. Carotid-artery blockage is not the only cause of a TIA. Bits of clots that have traveled to a brain artery from a distant site, such as the heart, are another common cause. That situation calls for blood-thinning medicines.

You definitely need further investigation and possible treatment right now.

Strokes are the third-leading cause of death in North America. The stroke story is told in the booklet on that topic. Readers can obtain a copy by writing: Dr. Donohue — No. 902, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.