DEAR DR. DONOHUE: I am an 82-year-old male. I exercise every day by walking as fast as I can, which is 108 meters a minute (3.6 miles an hour). If I try to walk faster than that, after about 15 minutes, I get nauseated. However, if I do empty my stomach, it is as if I get my second wind, and I can walk at that speed for much longer without any nausea.

Do people training for speed-walking or marathon-running have the same trouble, or is it my age that causes it? – T.V.

Exercise takes its toll on the stomach and the rest of the digestive tract. In a survey of marathon runners, 42 percent had digestive-tract symptoms during their runs. The symptoms included cramps, loss of appetite, diarrhea and even bloody diarrhea.

A too-full stomach is often the cause. It takes up to four hours for a heavy meal to leave the stomach. During exercise, blood is diverted away from the stomach and intestines to supply muscles. The circulation of blood to the digestive tract can drop as much as 80 percent. A full stomach doesn’t tolerate loss of its blood supply. I don’t know when you’re eating, but do so three hours before you start your walk, or wait until you finish it to eat. I’m not sure what you mean by “emptying” your stomach. I hope it isn’t what I imagine it is.

This diversion of blood is even more significant for someone your age. By 80, almost everyone has artery hardening and a buildup of plaque on artery walls. Plaque obstructs blood flow. Your stomach, therefore, not only suffers from a diversion of blood to your muscles, but it also experiences a diminished blood flow because its arteries have plaque in them.

Incidentally, has a doctor checked you over? You should have an exam before devoting so much time to such vigorous exercise.

If you do eat before you walk, cut back on the fiber in that pre-exercise meal. Fiber delays stomach emptying. Keep yourself hydrated. If you are on the dry side, circulation decreases even more.

DEAR DR. DONOHUE: In a few weeks I am taking 10 senior-high-school boys on a camping-conditioning trip. We are going to cover long distances from sunup to sundown, and we’ll camp wherever we end up. I plan on pushing the boys.

What can we eat while walking to keep energy levels high? Should it be carbohydrates? – M.L.

Blood sugar is depleted somewhat quickly with exercise, and then the body turns to glycogen for fuel. Glycogen is sugar stored in muscles. When muscle glycogen is gone, the body has trouble continuing its activities.

Snacking on carbohydrates keeps blood sugar in the normal range and stops the depletion of muscle glycogen so your campers’ energy will stay relatively high.

A drink with 8 percent carbohydrates would be a good source for you. Higher carbohydrate concentrations are not well-tolerated by the stomach when the body is physically exerting.

DEAR DR. DONOHUE: Please let me know if it is better to use a treadmill or an elliptical trainer for bone health. – L.S.

Which do you like to use? Use that one. Or, if you have access to both, alternate their use.

Weight-bearing exercise is the kind of exercise that benefits bones. Having to support body weight as well as having to cope with the tugging of tendons and ligaments on the bones causes the body to put down more calcium in them. Perhaps the treadmill noses out the elliptical trainer because you take steps on the treadmill. You lift your body up with each step. I don’t believe the difference is all that great.

The very best exercise for bone health is weightlifting, and that’s something that can be done at any age.

DEAR DR. DONOHUE: I have been diagnosed with cervical spinal stenosis and cord compression. I am 81 and do not want to have a neck operation.

The condition started with numbness in the fingers of my right hand about a year ago. Now I have it in the left hand. I take Lyrica, and it controls the numbness a little. Please help me understand this condition. – N.

Spinal stenosis indicates that arthritic backbones, backbone ligaments or spurs sprouting from the backbones are narrowing (stenosing) the spinal canal through which the spinal cord travels from the brain to your lower back. Your narrowing takes place in the neck region. The narrow spinal canal presses on the spinal cord and causes the symptoms you’re having. Often, this is something that comes with aging. If pain-relieving medicines, like your Lyrica, control symptoms and if they aren’t worsening, you don’t have to rush to surgery.

No one relishes the thought of an operation. If you have pain that’s unresponsive to medicine, or if the pain that is intensifying or if you have finger or hand weakness, you should consider a surgical correction.

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.

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