DEAR DR. DONOHUE: Both my daughters are volleyball players. The older one, now in college, doesn’t play anymore. In her senior year of high school, she tore her anterior cruciate ligament during practice, and that put an end to her athletics. The younger one, now a junior in high school, is on the varsity team. I am concerned she might suffer the same injury. What can she do to prevent it? – L.M.

ANSWER: The anterior cruciate ligament connects the front of the tibia (the larger lower leg bone) to the back of the femur (the thigh bone). It’s like a rope holding them together and functions as a stabilizer of the knee.

In contact sports like football, when a player has a foot firmly planted on the ground and an opposing player tackles him or in some other way collides with his leg, the anterior cruciate ligament often tears. The injury makes a popping sound, and the knee quickly swells with blood and fluid.

In noncontact sports – volleyball, basketball, skiing – the ligament tears when an athlete tries to slow down and simultaneously pivot. That motion puts enormous force on the anterior cruciate ligament and rips it in two.

Anterior cruciate ligament injuries are two times more common in female athletes than in male athletes. The wider female pelvis puts the female knee at a disadvantageous angle, and the ligament is more easily torn. Furthermore, the back female thigh muscles (the hamstrings) are weaker than the male hamstrings. This inequality between hamstrings and quads makes the female knee and the anterior cruciate ligament vulnerable to injury.

Your daughter can protect herself by doing squats with weights to strengthen her hamstrings. She should spent time in footwork drills too. The quads and hamstrings have to work in rapid sequence to protect the knee, and footwork drills can get them trained to respond quickly and correctly.

DEAR DR. DONOHUE: My husband and I are in our 50s and 60s and in reasonably good health. We walk outside every day, and we also walk on a treadmill. We lift weights at least three times a week. Our question is on conditioning. How do we know if what we’re doing is enough? What should our resting heart rate be? What should our heart rate be when we work out? We have heard that the state of conditioning can be told by how quickly the heart rate returns to normal after exercise, but we can’t get answers to our questions. Can you supply the answers? – B.M.

ANSWER: I can end this by saying you’re doing enough. You truly are.

The resting normal heart rate for an adult is between 60 and 100 beats per minute. Conditioned adults have a heart rate toward the lower end of that range. Highly conditioned athletes have resting heart rates in the 40s and even 30s. Their hearts pump more blood with each beat than do untrained hearts. Don’t try for those heart rates.

The exercising heart rate is obtained by subtracting your age from 220 and then taking 65 percent to 80 percent to bracket a so-called training zone. A good way of determining if your exercise is intense enough is to judge it for yourself. If it feels hard, it is hard. If it feels easy, it is too easy and needs more umph.

After exercise, the heart rate should slow by 12 beats after one minute of rest.

DEAR DR. DONOHUE: I bicycle for exercise, riding hard for 30 or more miles two to three times a week. I have some arthritic pains, but my doctor says I can continue exercising and manage any pain with naproxen (Naprosyn). He recommends I take it with omeprazole (Prilosec) to protect the stomach. When is the best time to take them? Do I take them together, at night, in the morning or with meals? – I.S.

ANSWER: Prilosec greatly decreases acid production. It should be taken half an hour to an hour before eating, because stomach acid, at a peak with eating, activates the drug. In two to five days, it reaches a maximal effect and stays there. The effect lasts 24 to 48 hours.

You can take the Naprosyn pretty much when you want to get maximum pain relief. Its peak action occurs two to four hours after ingesting it. It has a long half-life, meaning half of it is still working after 12 to 17 hours.

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.