Q: I've heard that weight-bearing exercises are a good way to prevent osteoporosis. Can you describe a few?
A: Use it or lose it: That message applies to most parts of our body. We see it most clearly with the muscles. If we don't use them, they wither. But if we regularly challenge them, they bulk up.
The same is true with bones. Most of our bones bear our weight, except when we're lying down. That's what they "want" to do. If we don't give them enough time each day to do that, they tend to get thin.
This is a particular problem if a person also has a genetic tendency to develop osteoporosis. Inactivity speeds the thinning of the bones that occurs in osteoporosis. This makes them more susceptible to fractures.
Weight-bearing (or strength-training) exercise is any activity that puts stress on bones. Walking and climbing stairs are examples. Weight-bearing exercises can help to slow bone loss and stimulate new bone growth.
A complete strength-training workout involves eight to 12 exercises. Together, they exercise all your major muscle groups.
Below, I'll describe three strength-training exercises. They are designed for older adults and people who are new to strength training.
Do strength-training exercises two or three times a week. Allow at least 48 hours between workouts. Try to do each exercise eight to 12 times, or repetitions ("reps"). These repetitions make up one set. Do two to four sets of each exercise. Rest for 30 to 60 seconds between sets.
To do these exercises, you'll need a sturdy chair, athletic shoes, an exercise mat and weights. (You should be able to do no more than eight to 12 reps of each exercise with the weights you choose.)
• Bridge: Lie on your back with your knees bent and your feet flat on the floor. Put your hands next to your hips with palms flat on the floor. Keep your back straight as you lift your buttocks as high as you can off the floor. Pause. Lower your buttocks without touching the floor, then lift again.
• Standing calf raise: Stand with your feet flat on the floor. Hold on to the back of your chair for balance. Raise yourself up on the balls of your feet, as high as possible. Hold briefly, then lower.
• Overhead press: Stand with your feet slightly apart. Hold a dumbbell in each hand on either side of your shoulders, at shoulder height, with your palms facing forward. Slowly lift the weights straight up until your arms are fully extended. Pause. Slowly lower the dumbbells to shoulder level.
I've put additional strength-training exercises, as well as illustrations of the exercises I've described above, on my website, AskDoctorK.com. You don't need to go to a gym; a small investment in buying exercise mats and weights allows you to do all the exercises at home.
• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com.