DEAR DR. DONOHUE: I recall an inquiry in your column pertaining to exercises for anyone trying to achieve his or her ultimate jumping ability. I have a teenager interested in basketball and volleyball. Any help you can provide would be appreciated. – J.V.

ANSWER: Plyometrics can increase jumping ability. It’s exercise designed to increase explosive power, like jumping. The exercises are a little tricky and put stress on the knees, so be careful. Only children who have reached puberty should attempt depth jumps. Younger children can jump consecutively. I’ll describe both.

For younger children, plyometrics is a second jump as high as possible done immediately after a first jump done from the standing position. The jumps are made in a series of five, or the child can take a break after the second jump and then begin from the standing position.

For older children, depth jumping is the plyometric exercise to increase vertical jump height. The jumper stands on a platform or sturdily constructed box, jumps off, lands with knees slightly bent and immediately jumps up again as high as possible. After the first jump, the athlete hurries back to the platform or box for the next jump and continues for five consecutive jumps. He or she then takes a three-minute break and then does five more plyometric jumps. Strong leg muscles are needed for this exercise, so the child or adult should be able to squat with 1.5 times body weight before attempting it.

The starting height of the box or platform is 12 inches. As skill improves, the height is gradually increased until it reaches 42 inches. The number of jumps also is gradually increased to eight successive jumps, and the number of sets is increased to three.

A rest of three days between these exercises gives muscles and joints a chance to fully recover.

Broad jumpers can benefit from plyometrics, too. Their jump after landing on the ground should be a horizontal one, like the jump they perform in competition.

DEAR DR. DONOHUE: I am a 97-year-old man who has always been athletic. Now I go to the fitness center and do five miles on the bike and perform machine exercises using 45 pounds of weight for an hour every other day.

I do get tired, but not excessively. The next day I have no ill effects. Is this too much at this age? – J.M.

ANSWER: My hat’s off to you. Age is no barrier to exercise, even weightlifting exercise. Your program would challenge people much younger than you.

Since you feel no ill effects, since you’re not panting for air during the exercise, it’s not too strenuous a program for you.

However, I have to add that you should check with your own doctor. That doctor knows you well, knows the state of your heart and knows what your capabilities and limitations are.

DEAR DR. DONOHUE: I was on my bicycle and was struck by a van. It caused me to flip off the bike. I had two broken ankles and three screws were placed in my lower back. I can’t sit or stand very long. Since then I have gained quite a bit of weight.

Do you have any suggestions on how to shape up and lose pounds? – J.D.

ANSWER: You have to cut back on your calorie intake, since your calorie burning is much less than it was.

As for exercise, have you tried water exercises – swimming or water aerobics? The buoyancy of the water eases stress on joints, bones and muscles, and you might be able to do more than you can do on land.

DEAR DR. DONOHUE: I’m not sure if you have covered torn knee meniscuses. I have had only an X-ray of the knee. I thought an MRI would be required before an orthopedist would go into the knee with a scope and do the repair. Are a mere physical examination and manipulation of the leg and knee sufficient to determine what the damage is? – M.B.

ANSWER: The meniscus is a C-shaped disc of cartilage in the knee joint. It serves as a cushion, protecting the knee from high-impact stress. Each knee has two meniscuses, a medial one and a lateral one. The medial meniscus is the one more often torn. About one-third of medial meniscus tears are sports-related.

What the patient tells the doctor can often indicate a meniscus tear. With a torn medial meniscus, squatting is painful. The knee catches when it is bent or straightened. Sometimes, it actually locks in place.

On physical examination, the McMurray test is quite useful in confirming the suspicion of a torn medial meniscus. The doctor bends the knee while turning the foot inward and then outward. If the doctor feels a thump in the knee joint, that is a positive test.

When signs and symptoms are typical, the doctor is fairly confident that the medial meniscus is torn and can insert a scope into the knee to confirm the diagnosis and fix it at the same time.

A standard knee X-ray doesn’t disclose a meniscus tear. An MRI scan does show such a tear, but it is costly and isn’t always necessary.