FALSE. While it's true that you stop building bone mass in your 20s, you can still do a lot to prevent it from being siphoned away. You can always make a difference, says Steven Hawkins, Ph.D., a professor in exercise science at California Lutheran University in Thousand Oaks, California. Case in point: The Harvard Nurses' Health Study shows that women of all ages who walked at least four hours a week had a 40 percent reduction in the risk of hip fractures, and post-menopausal women who walked at least eight hours a week had the same protection against fractures as those who took bone-boosting hormones. Getting enough calcium and vitamin D is also crucial, as is not smoking.
FALSE. Weight-bearing exercises like walking, high-impact moves like jumping, and strength training lead the charge when it comes to building bone, but that doesn't mean other activities have no value. "Anything that engages your muscles will have some positive effect," says Miriam Nelson, Ph.D. One recent review found that swimmers still built bone tissue at a higher rate than those who didn't exercise.
TRUE. Many physicians will order a DXA (dual-energy X-ray absorptiometry) scan to determine your odds for developing the disease. But it's also important to consider your muscle strength and balance, diet, and other lifestyle factors such as smoking or alcohol consumption -- they are an important part of the equation. "You have to look at the whole picture," Nelson says. Broach the topic at your next checkup by asking your doctor to help evaluate your risk. Be sure to discuss any family history of fractures or osteoporosis as well as your habits. (Be honest!)
TRUE. When pounds come off, you lose muscle mass along with fat tissue, and the less muscle you have, the weaker your bones will ultimately be. When you repeatedly gain and lose weight, you have less time to rebuild muscle.
TRUE -- AND FALSE. If you're sedentary, starting a walking program will strengthen your bones. But if you're already active, you might need to shake things up a bit. Three ways to do that:
Make an impact. If your joints are healthy, weave high-impact moves like jumping into your workout.
Move differently. Introducing new patterns -- like jumping side to side -- can "surprise" your bones and strengthen them. "Consider doing activities in which you move in a variety of directions -- like playing tennis, doing aerobics, or dancing," says Robyn Stuhr, sports medicine program director at the UC San Diego Health System.
Hit the weights. Whether you're lifting dumbbells or working against your own body weight (squats, pushups), resistance training stimulates bone-building. Be sure to include moves that work your hips (like squats and lunges), spine (lifting weights while standing), and forearms (bicep curls), because these are the areas most at risk for fractures.