Harvard Men's Health Watch

Strength training, Part I: Building muscles to improve health

In an odd sort of way, it's a case of science and medicine imitating movies and politics. In just a few years, Arnold Schwarzenegger has morphed from a symbol of muscle beach and cinematic mayhem to an icon of responsible governance and environmental stewardship. Similarly, strength training has been transformed from a cardiologist's nightmare to an important tool for improving health, even in cardiac patients. So although you may have long since abandoned the urge to display bulging biceps, you should understand why strength training is important for your health and how to do it properly.

As the clock ticks

Time takes its toll on all parts of the body; in the case of muscles and bones, the toll is particularly severe. Muscles get smaller and weaker as men age; it's a universal phenomenon that doctors call sarcopenia. You don't need a medical degree to see that 60-year-olds are weaker and less muscular than 20-year-olds. But you may be surprised to learn that muscle mass and strength begin to decline long before the changes are visible. The loss of muscle typically begins between the ages of 30 and 40 and progresses slowly throughout life; by age 60, the changes are obvious — and it's all downhill from there. In all, the average 30-year-old can expect to lose about 25% of his muscle mass and strength by age 70 and another 25% by age 90. That amounts to a loss of 2 to 3 pounds of muscle per decade, but the loss of muscle tissue does not usually cause a corresponding weight loss since body fat tends to increase as muscle bulk declines.

Bones show a similar pattern. They undergo a constant process of remodeling throughout life as new tissue is formed and old bone is resorbed. In youth, bone formation has the upper hand; that's how kids grow. In young adulthood, the processes are balanced, and bones are at their strongest. But beyond age 40, resorption outpaces bone formation; that's why older folks shrink. The loss of bone averages about one-half percent a year; in most men, the rate of loss is fairly steady, but in women, it accelerates sharply at about the time of menopause. Doctors can detect bone loss by measuring the mineral density of bones. When the loss of bone density is mild, it's called osteopenia, when more severe, osteoporosis.

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