GENERAL HEALTH

Fight Age With Muscle

The latest research is changing how doctors look at muscle mass. No longer seen simply in terms of performance or vanity, muscle mass serves as the body's armor against several age-related diseases as well as heart problems, diabetes and even cancer. By John Brandt, Best Life

Most men assume they are reasonably strong. Their muscle mass -- the aggregate of muscle tissue they have built over a lifetime, enabling them to support their bones, fill the legs of their jeans, and lift the heavy end of a sofa -- is at least adequate, relative to other men their age. Gianni Maddalozzo, PhD, (an exercise physiologist at Oregon State University) research focuses on the study of osteoporosis and muscle strength in adults ages 40 to 80. Most of his subjects suffer from advanced sarcopenia, the loss of muscle mass that occurs naturally -- and inevitably -- with age.

Compared with sarcopenia, other sneaky scourges of the middle years, such as arterial plaque buildup and prostate enlargement, announce their presence with a fanfare of symptoms. But sarcopenia creeps by in imperceptible increments, stealing a fifth of a pound of muscle a year, from ages 25 to 50, and then it picks up a dreadful, yet still mostly silent, velocity. The condition subsequently bleeds a man of up to a pound of muscle a year, a loss he is unlikely to notice until it's too late. "You haven't gotten any thinner, because the pounds of muscle are typically replaced by pounds of fat," explains Maddalozzo. "But sarcopenia is progressing all the time. One day you trip and fall and suffer a fracture of your hip. Then, when you try to rehab after hip-replacement surgery, you discover that you have virtually no muscle mass to build on."
Despite (or perhaps because of) its universal, inexorable nature, sarcopenia, until recently, did not get much respect. Indeed, until 1988, the condition lacked its own scientific name. "Historically, the scientific community has taken muscle for granted," concedes William Kraemer, PhD, a professor of kinesiology at the University of Connecticut. Perhaps more tellingly, sarcopenia's proven antidote -- resistance training -- will never make a dime for a pharmaceutical company. Scientists such as Kraemer, Maddalozzo, and a cadre of others are at the forefront of a movement that is redefining the importance of muscle mass in terms of overall health, not simply performance or vanity.

Recent research shows that diminished muscle strength and mass are empirically linked to declines in the immune system and the onset of heart disease and diabetes, not to mention weaker bones, stiffer joints, and slumping postures. Muscle mass has also been shown to play a central role in protein metabolism, which is particularly important in the response to stress, and decreased muscle mass correlates with a decline in overall metabolic rate (muscle mass burns more calories at rest than fat does). Further research is expected to show measureable links between diminished muscle mass and cancer mortality. The thinking about muscles and resistance training, in short, is reaching critical mass, and a major shift in the American fitness paradigm is under way. Along with this increasing emphasis on resistance training, there is an increasing awareness about the nutritional factors that can complement muscle growth, namely increasing daily intake of protein.

We used to discourage older adults from lifting heavy weights. Now we're telling them they can't maintain overall health without it. After age 50, you can't get by just doing aerobic exercise. Although it's not explicit yet in the government's overall health guidelines, agencies such as the Centers for Disease Control and Prevention now recommend a couple of rounds of resistance training a week. "Muscle function can improve -- sometimes robustly -- with resistance training, even after the onset of sarcopenia," says Robert Wolfe, PhD, a professor of geriatrics at the University of Arkansas. "But it is far more effective to begin resistance training before the process gains momentum. Intervention in the middle years is necessary."

The muscles of most men reach maximum size (or, strictly speaking, attain the maximum number of fibers per muscle) at age 25. From that lamentably early peak, a long, gradual decline ensues. Over the next 25 years, the muscles lose approximately 10 percent of their fibers. Then, starting around age 50, things go to hell. The body's production of testosterone, human growth hormone, and DHEA ebbs, and the motor cells of your nervous system, which spider out from the spinal cord to control the contraction of muscle fibers during physical activity, deteriorate rapidly. As the motor cells die, so do the fibers to which they're attached, especially type II or "fast-twitch" fibers, the ones employed for short bursts of anaerobic power. For instance, if your biceps consist of 90 fibers when you're 50 years old, by age 80, that number will be closer to 50 fibers, most of them feeble type "slow-twitch" fibers.

It's through the study of sarcopenia that a greater appreciation of muscle mass is evolving. Two seminal works, "Starvation in Man," an article published in the New England Journal of Medicine in 1970, and Hunger Disease: Studies by the Jewish Physicians in the Warsaw Ghetto, a book published in 1979, show that the depletion of muscle mass is the cause of death in human starvation. This is because essential organs and tissues such as the brain, heart, and liver rely on a steady supply of amino acids to synthesize new proteins and maintain function. Normally, dietary protein supplies these amino acids. Under duress, however, these organs maintain homeostasis by drawing protein from the muscles. Our skeletal muscle mass, besides powering all of our movements, also serves as a reservoir for our vital organs. And like all reservoirs, this one can run low -- or, in the case of starvation, run dry.

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