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Join Date: 03 Nov 2010
Location:  KuwaitPosts: 139 |
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Building Better Bones |
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Building Better Bones
It's a dangerous byproduct of aging you can't feel or see: your bones getting thinner and more fragile. But it may be possible to stem bone loss before full-fledged osteoporosis sets in with certain types of exercise. Journal Reports Read the complete Next: Living & Planning the New Retirement . While adequate intake of calcium and vitamin D are considered important for bone health, a growing number of studies show a strong association between exercise and improvements in bone mineral density—the amount of calcium in the bone. Because bone is living tissue, it responds to exercise by becoming stronger and denser. Studies indicate that the pull of muscle on bone stimulates the bone to grow, incorporate mineral and become stronger. In weight-bearing exercises with high impact—such as walking, jogging, racket sports and volleyball—bones and muscles work against gravity to build strength. And a combination of resistance and strength-training exercises not only helps build bone but also builds up the muscles that support the skeleton, improving balance and posture to help avoid the falls that lead to fractures. Some kinds of exercise don't do the job. Biking and swimming aid aerobic fitness and help trim and tone. But they aren't weight-bearing, so they generally don't appear to stimulate bone renewal. Warning Signs This all became relevant to me last summer, when I had a bone density test known as a DXA scan—an important screening tool that can detect low bone density and see if density has declined from a previous test. It showed I had lost 4% of the bone density in my spine and neck and 7% in my hips since 2006. My overall density is still in the normal range. But my favorite exercise is swimming, and osteoporosis runs in my family. So, I knew it was time to step up my regimen. Rather than stick to one form of exercise, a program that incorporates aerobic, weight and strength training is my best course, says Miriam Nelson, director of Tufts University's John Hancock Research Center on Physical Activity, Nutrition and Obesity Prevention. "It's not just about maintaining bone density, but about maintaining fitness," Dr. Nelson says. "Even if you have frail bones, if you have muscle strength and balance, you won't fall, and if you don't fall, you aren't going to have a fracture." Osteoporosis, or porous bone, now affects 10 million to 12 million people older than age 50. And as many as 47 million people with low bone mass—known as osteopenia—are at risk for future osteoporosis. The problem is that the body fails to form enough new bone, reabsorbs too much old bone, or both, increasing the risk of fracture. As many as half of all women and a quarter of men over 50 will break a bone due to osteoporosis, according to the National Institutes of Health. That can quickly lead to a worsening quality of life, more fractures and even death: An average of 24% of hip-fracture patients age 50 and over die in the year following their fracture, according to the National Osteoporosis Foundation. Consistent Results The exact role of exercise in the prevention of bone loss is still somewhat controversial. So far, most studies have been performed on relatively small groups of women, and in some, participants also received nutritional supplements or hormone replacement therapy. Even so, says Scott Going, a professor of nutrition and physiology at the University of Arizona, studies of resistance training consistently show gains in bone mineral density of about 1% to 3% at the most critical hip and spine areas in premenopausal and postmenopausal women. (That's roughly equivalent to preventing one to four years of decrease in bone density in postmenopausal women and older men). Fewer studies have been done in men, but Dr. Going says findings are similar. The University of Arizona's Bone Estrogen Strength Training Study, or BEST, conducted from 1995 to 2001 on women ages 45 to 65, found that weight-bearing and resistance exercises over a one-year period, combined with a calcium supplement, significantly improved bone mineral density at fracture-prone areas. The study was funded by the National Institutes of Health and the calcium supplement Citracal, now owned by Bayer HealthCare. (A recent study in the British Medical Journal has raised concern about calcium supplements, finding a 30% higher risk of heart attack in healthy older women who took them.) |
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