DEAR DR. DONOHUE: Last school term, before summer vacation, I asked my coach what I could do to improve the distance I throw a football. I would be first-string quarterback if I could throw farther. He told me to lift weights during the summer. I did — all summer long. I can throw a bit farther, but not enough to get me to the first string. Why not? — B.Z.

ANSWER: It’s a funny thing about weightlifting. It always is a stimulus for muscle growth and muscle strength. It’s not always a benefit to sport performance. The reason is that muscle training to improve a specific sport task requires the athlete to mimic the actual movements and sequence of muscle contraction that takes place when doing that task. In other words, to throw a football farther, you have to imitate the throwing motion with weights.

That’s not always easy. Sport-specific motions are complicated and quite hard to imitate with weights. You can, however, approximate the motions by using light weights held in one hand. Don’t go overboard with this at the start. You can hurt muscles and joints that are not used to this kind of overloading. You not only have to imitate the motion, you have to duplicate the speed of the motion, too.

Specificity of training applies to all sports. It holds for swinging a bat, hitting a tennis ball, driving a golf ball, swimming and every sport endeavor.

Overall strength training is a must. But so is sport-specific training if you want to improve a particular aspect of a sport.

DEAR DR. DONOHUE: I am a 49-year-old female. I weigh 250 pounds and am 5 feet 3 inches tall. I work five days a week in health care.

My doctor tells me I have arthritis in my hips, knees, feet and back. I take Aleve. I walk two miles. It takes me an hour. By then, my joint pain is 10 on a scale of 1 to 10.

I am considering having lap band surgery. If I do, do you think the weight loss will help much with my joint pain? I cannot lose weight because of my joint pain. I have tried many ways to treat it. All I ever get is short-term results. — Anon.

ANSWER: I can almost guarantee you that your joint pain will greatly decrease if you lose weight. Weight loss is one of the things every doctor advises osteoarthritic patients to do. Providing a guarantee in medicine is close to impossible. I did put an “almost” in front of my guarantee.

Your body mass index puts you in the category of dangerous obesity. Not only will you benefit your joints, you’ll benefit your heart and all body organs. If surgery is the only way that you can take off pounds, I’d seriously consider having it done.

DEAR DR. DONOHUE: I work in a cubicle with a guy who says he exercises at his desk. He’s quite muscular, so I believe him. Our desks are firmly attached to a cement floor. He exercises by trying to push his desk. He says it builds muscles even though the desk doesn’t budge an inch. Is this possible? — R.R.

ANSWER: It is. The exercise is isometrics. With isometrics, muscles don’t shorten or lengthen as they do in standard exercise. If you perform a biceps curl, for example, you hold the barbell at waist level, bend your elbows and lift the bar to your shoulders. When at that position, your biceps bulge. They’ve contracted. When you lower it, the bulge goes. The muscle has lengthened. In isometrics, muscles don’t move.

A near-maximal strain against an immovable object strengthens muscles. You have to vary the position of your hands if you want to get symmetrical growth and improvement in muscles through isometrics. It works, but not as well as weightlifting works.

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.