DEAR DR. DONOHUE: I am 41-year-old woman who has exercised my whole life. I have four active children and a marathon-runner husband. I have a moderate body weight and am a healthy eater. I exercise every other day for 40 minutes and keep my heart rate between 170 and 180 beats a minute. I’ve been told this is too high. Is it dangerous? – J.H.

ANSWER: The only way to get a definite answer to your question is to undergo a maximal stress test where an EKG is continuously recorded while you run at the heart rate you reach during your exercise sessions.

In lieu of a stress test, you can estimate what your maximum heart rate is by subtracting your age from 220 – for you, 180. Your highest exercise heart rate is supposed to be 85 percent of that number – 153 beats a minute in your case. No one knows if exceeding that number poses a health threat. But be advised this formula for determining maximum heart rate has an inherent error of plus or minus 15 beats. Theoretically, therefore, your highest exercise heart rate could be 168, very close to 170.

Others ignore the above and say that a 40-year-old can safely get the heart beating up to 200 beats a minute.

Another rule tells people that the heart can beat safely 113 times above the resting heartbeat (pulse). If your resting pulse is 80, by this rule you can raise the heartbeat to 193 without danger.

All these rules – and there are more – are rough approximations at best, and the actual ceiling for a heartbeat is unknown. You can eliminate the arithmetic and formulas by paying attention to what your body tells you. If you’re not gasping for air, if the exercise doesn’t completely wipe you out, then you’re exercising at a level that’s not hurting you.

DEAR DR. DONOHUE: I am a 66-year-old female. I joined an aqua-exercise program held at a local apartment’s indoor pool. The pool was not really clean. On one occasion it was so dirty that it smelled, and you could not see through the water. A short time after joining the class, I developed what looked like shaving bumps under my arm. A physician’s assistant said it was folliculitis and put me on antibiotics. The bumps went away but came back two weeks after finishing the medicine. I saw my family doctor, who declared I had scabies, and he gave me permethrin and Hibiclens (an antibacterial liquid soap). He said I could have gotten it from my dog. Could I have gotten this from the pool? The sponsors said that staph is everywhere and won’t give me a refund. – N.R.

ANSWER: Scabies is caused by a very minute mite that burrows into the skin, making tiny tunnels that look like wavy, thin, short lines. The human scabies mite lives only on human skin. You catch it from people who are infected. Dog mange, another mite disease, looks a bit like scabies but doesn’t last long, since it cannot survive on a human host. Itching, worse at night, is the outstanding feature of scabies. Permethrin cream is effective treatment for it.

Folliculitis, a more likely diagnosis, is caused either by Staph or by a bacterium with the name Pseudomonas (sue-doe-MOE-nuss). It’s an infection of hair follicles. It’s seen as small, red bumps. Usually folliculitis is a self-limited condition – it gets better on its own. For Staph infection, antibiotics might be needed. Pseudomonas can be picked up in unsanitary swimming pools or hot tubs. Perhaps the Hibiclens you used shortened its duration.

The sponsor’s remark is inane. Staph and other germs are everywhere, but they don’t cause infections because their numbers are small. In the pool where you exercised, the numbers of bacteria were most likely great.

DEAR DR. DONOHUE: I have Crohn’s colitis. Would performing abdominal crunches adversely affect my condition? – T.W.

ANSWER: Unless you were having a flare of the colitis, exercising – including doing abdominal crunches – should not cause any trouble.

Did you know that two former National Hockey League players, Theo Fleury and Kevin Dineen, are Crohn’s patients? Few sports demand the amount of physical exertion that hockey does.

DEAR DR. DONOHUE: I am a 71-year-old man and am concerned about the possibility that I have breast cancer. Some time ago, I started having pain in my left breast and thought I felt some lumps. There is a decided difference in the two breasts. The affected one sags, while the other is firm. I asked my doctor about it, and he ordered an ultrasound of the breast, which proved to be negative for cancer. Do you think another exam of my breast is in order? My family has a history of breast cancer; two sisters and a niece have had it. – H.F.

ANSWER: Men do get breast cancer, but not in the same numbers that women do. There is only one case of male breast cancer for every 100 cases of female breast cancer.

For men, as for women, the most frequent sign is a painless lump, and for men, the lump is usually in the center of the breast beneath the nipple. The lump most often is fixed to underlying tissue. You can’t push it around like you can noncancerous lumps. The nipple might ooze a discharge, either bloody or not.

A family history of breast cancer, even in female family members, slightly increases the risk for a man to come down with it.

In your case, the chances of cancer are very slim. Apparently your doctor did not feel a suspicious lump. The ultrasound picture of your breast did not show any abnormality. The fact that your breasts are unequal in size could be explained by simple accumulation of fat and breast tissue in one breast and not in the other. That can happen with age.

If this matter leaves you uneasy, then seek a second opinion. Get a mammogram. If the second doctor and the mammogram don’t produce evidence of cancer, forget the matter.

The booklet on breast cancer is devoted to a discussion of female breast cancer. Readers who would like a copy can obtain one by writing: Dr. Donohue – No. 1101, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 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. Readers may also order health newsletters from www.rbmamall.com.