Walking may be the best all-around exercise, but as far as bone building goes, strength training is the cream of the crop. The pull of muscle against bone stresses a bone, and that kind of stress is what makes a bone become stronger. Impact also strengthens a bone, but the impact that comes from running or jumping, say, can be otherwise harmful to the body. Muscle working against gravity provides another kind of impact for the bones, stimulating bone formation and slowing loss. Strength training with free weights (including light hand and ankle weights) or weight machines is the most direct way to provide that stress and impact of muscle on bone, which is what makes it ideal for building and preserving bone density.
We know that weight lifters have much denser bones in their back and legs than do runners, for example. Studies do show that walking prevents bone loss in the spine, but strength training has been proved to build bone mass in the spine and hip. One study that (deservedly) got a lot of media attention followed a group of postmenopausal women who were generally healthy—but sedentary. None were taking HRT, or any other bone-related medicines, or taking calcium supplements. Half performed a simple weight-lifting routine twice a week, while the other half stuck with their couch potato ways. After one year, the weight lifters built their bone mass 1 percent on average, at both the hip and spine. That compares favorably to what you’d see with HRT alone. To give you perspective, consider this: the women who did not lift weights lost up to 2.5 percent of their bone mass over the same time period— and also lost muscle mass and gained body fat and weight. The weight lifters became much more active in general (as the researchers calculated it, a 27 percent increase), while the sedentary group became less active. The weight lifters lowered their body fat, gained muscle, and had better balance and more strength. And here’s a wonderful bonus: the researchers had the daughters of the women who lifted weights come in and do the tests their mothers were acing. In every case, the weight-lifting women outperformed their own daughters!
I only wonder how much better they might have done if they also took calcium. Or HRT: another study looked at women taking HRT after surgical menopause, and found that after a year of strength training the average increase in bone density was 4 percent in the wrist and 8 percent in the spine!
Building muscle also increases your metabolic rate—that is, how fast your body burns calories at rest. Think of your metabolism like a fire: a large fire produces more heat and uses more fuel than a small fire. Exercise stokes the flames of your metabolism. That is increasingly important as you age, because your metabolism usually slows as you get older, partly because of muscle loss. Muscle mass begins to decrease in midlife unless you are active. Strength drops, on average, about 15 percent during your sixties, and another 15 percent in your seventies, and 30 percent each successive decade. This is not a result of aging, but of inactivity.
Muscle uses more calories to maintain itself than fat does. The stronger you are (the more muscle you have), the more calories you will burn at all times and the easier it will be to control your weight—and the more you will need to eat to stay at the same weight. Weight-loss diets typically fail because you don’t permanently change the way you eat and work. Restricting the number of calories you take in results in muscle loss, not fat loss. You also end up in double jeopardy because if you just reduce the calories you take in (as opposed to increasing your body’s caloric requirement, with exercise), your metabolism slows to accommodate only the lower number of calories. So when you increase them again (going “off ” the diet), all you will have done is set yourself up for immediate weight gain.
Muscle also helps the body use sugar efficiently, so strength training is an important addition to a diabetes treatment or prevention program. Losing muscle reduces your sugar tolerance. Strength training has been shown to prevent weight gain, fractures, and injury, and to lower the risk of heart attack and colon cancer in ways aerobic exercise alone does not. Loss of muscle impairs your body’s ability to regulate its temperature, too. Just one strength workout a week is enough to prevent the muscle loss that accompanies aging, even in devoted athletes who focus only on cardiovascular exercise. Increasing your strength lowers the risk of injury to joints and muscles. It also improves your balance and so reduces your risk of falling, which in turn reduces the risk of fracture.
As with every other strategy in this book, it is never too late to benefit from strength training. One study of people in their 80s and 90s living in nursing homes who exercised with weight machines three times a week for just eight weeks showed improvements in strength, balance, and walking speed. Even people who are already frail can, with proper exercise using light weights, build up enough leg strength to walk without a cane. I’ve no doubt of the bone benefits that went along with these results, even though they weren’t tracked by the researchers.
Studies show that two 15-minute strength workouts a week is enough to build bone density. As you’ll see in the next chapter, you can target all the major muscle groups with a very compact routine, which should take you no more than about 20 minutes once you’ve got it down. If you prefer machines to hand weights, a thorough workout may take a bit longer just because you need time to adjust each piece of equipment properly before you use it. You should rest at least one day between sessions to allow your muscles to recover, because it is during the recovery period that muscle actually grows. If you want to exercise every day, just alternate which group of muscles you work on which days—that is, do upper body one day and lower body the next. Once you start a regular routine with weights or weight machines, your bones will be denser before a year is up. But if you stop, you’ll start losing bone again immediately. As with dieting, you have to think of embarking on a fitness program that includes strength training as a lifetime plan, not a solution you achieve in a set time period, then don’t have to work on anymore.
*118\228\2*