DEAR DR. DONOHUE: You ran an article in which you asserted that “no pain, no gain” was “one of the most inane sayings ever mouthed.” If you are talking about joint, tendon or muscle pain, you are correct. But what most exercise gurus mean by that phrase is the fatigue brought on by exercise stress. Mild to moderate fatigue is a good thing. The body has to be stressed to achieve fitness. Please comment. – J.T.

ANSWER: By “no pain, no gain” being a cliche that can get people into serious trouble, I meant that anyone with an injury should not play in spite of the injury. I also meant that playing when sick is another invitation to irreparable harm.

I didn’t mean the muscle soreness that comes from challenging the body. That is mostly good and should not be a signal to stop exercising or playing.

During any exercise routine – say, weightlifting – muscles begin to hurt. That’s due to a buildup of lactic acid, a byproduct of energy combustion, and due to a depletion of the energy molecules that keep muscles moving. This kind of hurt promptly goes away in a matter of a few minutes with rest and isn’t a warning to stop exercising.

Muscle pain and stiffness that comes on the day after exercising at a greater than usual intensity is an expected consequence of hard work. It’s OK to continue to exercise when in this kind of pain, but it should be at a lesser level.

Muscle pain that begins 48 hours after exercise is a different kind of muscle injury, a slightly more serious kind. The insulating tissues around muscles and muscle fibers themselves have been pummeled, and they need a rest. They don’t need a complete rest, but they should be exercised at a lower level, and it can take them a week to recover fully.

DEAR DR. DONOHUE: I am 18 and into bodybuilding, which I’ve been doing for three years. I have achieved some success, but not the success I want and not the success I see others have gotten. I know many of them are on steroids.

I am considering trying them too. I don’t think I will ever get the size I want without them. I would like the truth. Are they really dangerous? Do they really work? – D.F.

ANSWER: The word “steroid” creates confusion. One class of steroids is the cortisone drug family. Prednisone is a much-used member of this family. These steroids have a place in medicine to fight inflammation.

The steroids you’re talking about are muscle-building (anabolic) steroids, male hormones. They have a limited place in medicine but no place in athletics. They really do work. They produce rapid gains in muscle growth.

They are dangerous. They cause breast growth in men and breast shrinkage in women. They shrivel the testicles. They might enlarge the prostate gland. They cause acne and hair loss. They can weaken tendons. They’re reputed to cause heartbeat abnormalities.

You don’t want to use these steroids.

DEAR DR. DONOHUE: My 6-year-old granddaughter has been diagnosed with molluscum contagiosum. She has several spots on her back, a few on her legs and some under her arms. A cream was prescribed. The spots started bleeding a bit. After using three tubes of cream without success, she was referred to a dermatologist, who agreed with the diagnosis. He has her on a new schedule. He applied some sort of acid and taped the molluscum spots. The parents were told it could take two or three applications.

Friends of theirs have a boy who had the same problem. His parents did nothing, and the molluscum left. Would you recommend doing nothing or taking the course that my granddaughter’s parents have taken? Is this a serious problem? – N.O.

ANSWER: Molluscum contagiosum is a common skin infection caused by a virus. It is seen in children between the ages of 3 and 10, but it is not exclusively a childhood infection. It can and does infect adults. It isn’t a serious condition unless the infected person has a defective immune system. If that is the case, the infection can become widespread.

The “spots” she has are very tiny, dome-shaped, pearly bumps with a depressed center. They look a bit like miniature volcanoes. With pressure at the base of the bump, cheesy material can be expressed through the center.

Molluscum doesn’t have to be treated. In favor of doing nothing is the fact that it usually leaves in six to nine months. Furthermore, the virus doesn’t make the child ill. Usually it’s only the sight of the molluscum that pressures parents into treatment.

In favor of treatment is the fact that the virus can spread to other skin sites and an infected child can spread it to playmates.