DEAR DR. DONOHUE: I am a 37-year-old man and have been athletic all my life. Since age 30 I have engaged in a program of weightlifting and running. I am not bragging when I say I am in good shape. However, I am scheduled to have foot surgery, and the doctor estimates it will take eight weeks for me to recover. What’s that going to do to my level of fitness? – P.R.

ANSWER: Deconditioning is something that concerns every athlete and every person interested in fitness. It’s something of profound concern for astronauts, who are forced to spend long periods in gravity-free environments where they cannot exercise.

As far as cardiovascular fitness (aerobic fitness) goes, there is a steady decline in heart function in the first three weeks of enforced rest. After that the decline continues, but at a slower rate.

You might be off your feet, but you can still perform aerobic exercises. You can use a rowing machine, and that provides the heart with as much training effect as running does. That’s only one example of a way to maintain cardiovascular conditioning when you’re off your feet.

As far as muscle strength goes, the decline is said to parallel the time it took to build strength. For example, if a person has been lifting weights for six months, that person can expect to lose in three months of inactivity half of what was gained during the six-month period of exercise.

This bit of news doesn’t have to be depressing. If a person cuts back the volume of exercise to only one session a week, he or she can expect to maintain the gains that have been made. You can do upper-body weightlifting exercises off your feet. You can even do thigh-muscle exercises sitting in a chair.

DEAR DR. DONOHUE: My question is related to the letter regarding triceps exercises with barbells. I am 5 feet 4 inches tall and weigh 108 pounds, but my triceps are flabby and jiggle. I would like to have tight triceps like those of the late actress Barbara Stanwyck. How did she get them? – A.J.

ANSWER: I don’t know. I suspect genes had much to do with it.

For readers, triceps are the muscles on the backs of the upper arms. The triceps is an area that seems to get flabby for many women – and men.

I can give you a triceps exercise that doesn’t involve any equipment. It’s the tried-and-true pushup.

Lie on the floor, face down, with hands under the shoulders. Raise the body upward so all body weight is supported by the hands and the toes, keeping your body straight. Then lower the body down to the floor and repeat the up-and-down movement as many times as you can.

This is a difficult exercise, and many beginners find it impossible. It’s OK to cheat. You can do a modified pushup by letting your knees prop up your body weight as you raise yourself off the floor. Once you gain strength, you can adopt strict pushup form, where the only support of body weight is the hands and toes.

DEAR DR. DONOHUE: I am 77 and have just incorporated deep breathing into my laps at the pool. I had been doing 50 laps until I started the deep breathing. Now after I do 15 laps I get lightheaded and can hardly walk to the showers.

Should I cut down on the laps or the deep breathing? Is it dangerous to have lightheadedness? – L.H.

ANSWER: Lightheadedness is not a good sign. It can mean that insufficient blood is getting to the brain, or it can come from a change in body chemistry. In deep breathing you might be flowing off too much carbon dioxide and upsetting the body’s acid-base balance. That can make a person lightheaded. Stop the deep breathing and see what happens.

If the sensation doesn’t go away, then you really must see your doctor. Something more sinister might be going on, something unrelated to your new breathing style.

DEAR DR. DONOHUE: My doctors have been monitoring my white blood cell count, which runs between 6,000 and 12,000, for the past 35 years. For the past five years, I have lived in the United States and cannot have a blood count done because I have no health insurance. I have never been sick and feel well now. What causes a high white blood count, and what does it do to the body? – S.M.

ANSWER: The normal white blood count ranges between 4,500 and 11,000 (some put the upper limit at 10,000). At times yours has been slightly higher than the upper limit. You have never been sick. You feel well now. Forget your white blood cell count. For you the slight elevation is simply an idiosyncrasy. It’s not doing you any harm.

High white blood cell counts – much higher than yours – are found with infections, tumors, inflammation, trauma and stress, both physical and mental.