DEAR DR. DONOHUE: I am a 59-year-old male and have been jogging for 25 years. In the winter months I used to use a NordicTrack. Last year I switched to an elliptical cross-trainer. I have read how running backward develops muscles around the knee joint. Does using the elliptical trainer in a backward motion have any benefit? If so, what is the recommended cycle? Five minutes forward and five backward? – M.H.

DEAR DR. DONOHUE: What gives with backward running? It looks dumb. Is there something to it that I don’t know? – B.R.

ANSWER: Let’s take the running question first. What’s said about running can apply to the elliptical trainer.

Running backward exercises leg muscles that are not used as much as in forward running. It provides muscle balance for the legs, including the muscles that protect the knee joint.

The energy cost of backward running is one-third greater than the energy cost of forward running. You burn considerably more calories in the same time when you run backward than you do running forward. In backward running, the feet hit the ground faster than they do in forward running, and it takes more energy to propel the body backward. Those are two explanations for the increased calorie burning of backward running.

On an elliptical trainer, the calorie cost of backward pedaling might not be much different from forward pedaling, but you are using different muscles. The buttock muscles, in particular, are worked harder when a person pedals backward, so you are balancing muscle development.

Your program of five minutes forward and five minutes backward makes sense. If you want, you can alternate days of forward pedaling with days of backward pedaling.

DEAR DR. DONOHUE: I have a step-counting pedometer and would like to know how many steps I should take in a day. Can you also tell me how many steps make a mile? I am 80 years old and fairly healthy. – J.B.

ANSWER: About 2,000 steps make a mile. The actual distance depends, of course, on the length of your step.

At a brisk pace, the average person takes about 4,000 steps in a half-hour. That depends on how fast a person steps.

Two thousand steps burn 100 calories.

Exercise experts want people to take 10,000 steps a day – 5 miles. A sedentary person takes between 4,000 and 6,000 steps a day.

Would you like to be let in on a secret? You are 80 years old and in fairly good health. The way you have lived life has served you in good stead. You don’t need to listen to experts. You are an expert. We should be listening to what you have done.

DEAR DR. DONOHUE: My husband and I have a disagreement on the exercise I am doing. I have a Gazelle by Tony Little. I exercise on it for one hour without the tension rods turned on. That’s where the fight begins. My husband says I am wasting my time without turning on the tension rods. I say that as long as I keep my heart rate up, it is helpful for me. I can go only about five minutes with the tension rods on. What is your opinion? – D.W.

ANSWER: All of us have seen Tony Little on television suspended on a machine with his feet on pedals and his hands holding on to moveable bars. The bars and pedals move in unison in a sort of skiing motion.

If you get your heart beating in the exercise zone, you are benefiting heart and blood pressure. Subtract your age from 220. Then take 65 percent of that number. That is the lowest heart rate that constitutes aerobic exercise. Maintaining that heart rate for 20 minutes is the basis of aerobics. You do it for an hour. That’s great.

If you want, toward the end of your session, turn on the tension rods for a few minutes. They add to the strenuousness of the exercise. If you can add a minute more every week or so, you’ll be benefiting yourself even more.

DEAR DR. DONOHUE: Do diuretics retain calcium, or do they eliminate it? I know they eliminate potassium, but how about calcium? – E.G.

ANSWER: It depends on the diuretic (water pill). Diuril and HydroDIURIL, two commonly prescribed diuretics, keep calcium in the body. They are sometimes used for the treatment of osteoporosis.

Bumex and Lasix, on the other hand, promote calcium’s passage into the urine.

Not all diuretics draw potassium out of the body. Aldactone conserves it.

If you care to name the diuretic you’re interested in, I’ll tell you what its effect on calcium is.

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. Readers may also order health newsletters from www.rbmamall.com.