DEAR DR. DONOHUE: I hope you can help me with a problem that might get me kicked off the first string. I get cramps in my legs, mostly in the calves. At first, it was laughable. Now it’s not. At practices, I can sit down and wait for the cramp to go. During a game, I have to be replaced. How do I stop them? — B.L.

ANSWER: I have to tell readers what I say applies to exercise-associated muscle cramps and not to the cramps that so many older people get when in bed. They’re both the same phenomenon, an involuntary, sustained and painful contraction of a muscle or muscles. But they’re not the same when it comes to the situation that brings them on.

The actual cause is a matter that experts have debated for years. A lack of potassium, calcium or magnesium, excessive exercise, cold weather, hot weather and dehydration have been cited as possible causes. None has been proven to be the universal cause. Muscle fatigue is another possibility. Some experts say that muscle fatigue affects the muscles’ response to spinal cord signals that prevent cramping.

Suggestions to forestall cramps are many. Hydration is a reasonable approach. An hour before a game or an exercise session, drink a quart of water. That gives enough time for the water to be absorbed. During play, keep drinking. If you are drinking a lot of fluid, switch to a sports drink to prevent a drop in potassium and sodium. Stretch your calf muscles in three daily sessions. Rising on the toes is a good calf stretch. You can try taking a vitamin supplement that contains most of the B vitamins. Make sure vitamin B-6 is included.

To uncramp a muscle, sit on the floor with the involved leg stretched out in front of you. Grab the ball of the foot, and, while keeping the heel on the floor, pull the foot toward you and hold it in that position until the cramp eases.

Pinching the skin between the nose and the lip is another way to break a cramp.

DEAR DR. DONOHUE: What’s your opinion on massage? I started a bodybuilding program with two friends, and we go at it quite ferociously. We’re over the first weeks of muscle soreness. One of my friends gets a massage after each session. He talked me into joining him. I did, and it worked wonders for me. — K.C.

ANSWER: I’m all for massage. It has found an honored place in sports medicine. It loosens tight muscles. It increases blood flow to exhausted muscles and helps replenish their exhausted stores of fuel. In the same way, it carts away waste products generated by heavy exercise.

The fact that you find it does wonders for you is enough reason to continue.

DEAR DR. DONOHUE: I am a recent owner of a treadmill. It has more gadgets and gauges on it than I know how to use. I’m gradually learning.

One gauge gives a reading of “mets.” Will you enlighten me at to what this is? — H.K.

ANSWER: A “met” is short for “metabolic equivalent.” It gives exercise intensity in a form other than the more familiar calories. To be exact, a met is the consumption of 3.5 ml of oxygen per kilogram of body weight per minute of exercise. I’m pretty sure that definition is totally unhelpful.

Let me give you some examples that will help clear the met matter up.

One met of exercise is simply sitting calmly in a chair.

Three to five mets is comparable to raking leaves or walking at a pace of 3 miles an hour.

Jogging at 5 miles an hour is five to seven mets.

Shoveling heavy, wet snow or playing basketball with few breaks puts this kind of exercise in the nine mets or greater range.

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.