DEAR DR. DONOHUE: You wrote something about eccentric muscle contractions. I didn’t understand your message. Would you go at it again for me? I am quite interested in strength training, and I am even more interested in the scientific basis of it. I plan to make a career in sports medicine. – H.H.

Let me give you an example to get the message across. The barbell curl exercise can clearly fix the idea of eccentric muscle contractions in your mind.

The curl is done with the barbell held at waist level with the hands holding the barbell in an underhand grip; the palms face upward. The person lifts the barbell to the shoulders in a curling motion. The biceps muscles – the muscles on the front of the upper arms – contract. Those are the muscles that cool guys love to flex for an admiring audience. Popeye flexes his all the time. During the biceps contraction, the muscles are shortening. That’s a concentric contraction.

In lowering the weight back to the starting position at waist level, the biceps muscles lengthen. They’re still working. If they weren’t, the weight would come crashing against the thighs at great speed. This sort of muscle work, done while the muscle fibers are lengthening, is an eccentric contraction.

Eccentric contractions stress muscles more than concentric contractions. You would not think that’s the case, but it is. All effort is intuitively spent on raising the weight, not lowering it. However, the lowering motion is more important for muscle growth and strength gains than is the raising motion. That’s why a return to the starting position should be done with deliberation and slowness. It should take a person twice as long to lower the weight as it does to raise it. Don’t let the weight come back to the starting position in a fast and uncontrolled manner.

Since eccentric contractions are so taxing, they often lead to muscle soreness. You shouldn’t overemphasize eccentric exercise, but you should take advantage of it.

DEAR DR. DONOHUE: I read about athletes taking steroids. I also read about steroids being used for many medical conditions. Asthma comes to mind. They can’t be the same. Are they? If not, what’s the difference? – R.P.

“Steroid” is an unfortunate word. It includes a large number of substances – drugs and natural hormones – that have only one thing in common: their chemical structure.

Athletes take male-hormone steroids, compounds similar to testosterone. These steroids are called anabolic steroids – stimulating growth. They build muscles and increase strength. Their use for medical conditions is quite limited. Their use in sports is banned.

Steroids used in medicine belong mostly to the drug family that fights inflammation. They are the cortisone group of steroids, and prednisone is the one most often prescribed. These hormones are employed for hundreds of medical conditions. They have nothing to do with muscle-building. This is the kind of steroid sometimes given for asthma control.

DEAR DR. DONOHUE: As a retired grandfather, I have lots of time on my hands. I spend some of it watching my grandson both practice football and play football games. His coach has the team do plenty of exercises, including squats.

When I was a youngster, I also did squats. I later learned that the squat exercise is bad for the knees. Should I ask the coach why he’s having these young boys do that exercise? – S.W.

Squats are a good exercise for thigh muscles. They can be hard on the knees if the squatter lowers him- or herself so that the buttocks almost touch the heels. It’s not necessary to go so low. It’s necessary to lower oneself only to the point where the thighs are parallel to the ground.

If your grandson and his teammates are squatting lower than that, you could discreetly ask the coach if a modification of the exercise would be better for them and their knees.

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

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