Health

Muscles matter: Physicans advised to tell patients to build up strength

People have been jogging for years. But lifting weights? Not so much. It's time to rethink the importance of resistance training.

By Susan J. Landers — Posted Sept. 15, 2008

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Jeff Williamson, MD, a geriatrician at Wake Forest University School of Medicine in North Carolina, can be persuasive about the benefits of building muscle. "I like to say there are really only two reasons why older people end up in a nursing home. One is that their brains stop working, and the other is that their muscles stop working. Especially their leg muscles."

While the loss of skeletal muscle inevitably comes with aging, no one should just sit still and take it. In fact, sitting still would be the worst thing. People in their 40s and 50s need to take prompt action to preserve what strength they still have, said Dr. Williamson, clinical director of the J. Paul Sticht Center on Aging and Rehabilitation at Wake Forest.

Muscle loss probably starts around age 40 for some people and by age 50 for most. But young, sedentary people likely will arrive at later life with less muscle than those who are more physically active, said Roger Fielding, PhD, director of the Nutrition, Exercise Physiology and Sarcopenia Laboratory at Tufts University in Boston. That circumstance could set them up for more disability in later years.

"We are becoming much more aware now than at any time in the past that as people get older, the amount of muscle they have in their body becomes smaller," Fielding said.

It only has been during the past decade or so that imaging techniques have captured this muscle loss, noted Dr. Williamson. These advances have allowed physicians to quantify how much muscle people should have at certain ages and to develop outcome measures to test interventions that are intended to preserve muscle.

General consensus surrounds the idea that physical inactivity plays a big role in muscle loss. "We see pretty large declines in strength in people because they don't maintain activity," said Barbara Bushman, PhD, a professor of health, physical education and recreation at Missouri State University. In one study, 40% of women ages 55 to 64 said they couldn't lift 10 pounds.

"We suggest that people get a dog and walk the dog for exercise, but then they can't even lift a 10-pound bag of dog food into their car," she said. The numbers are even worse for women 75 and older -- 65% said they couldn't handle that amount of weight.

"To me, that's pretty frightening," Bushman said. "They couldn't lift a grandchild or respond in an emergency situation."

Lean body mass decreases about 15% between ages 30 and 60, she said. "It comes down to about five to seven pounds of muscle lost each decade."

Although it's probably never too late to try to regain strength, the middle years -- starting at age 40 -- are a key time to pick up the weights.

"It's like saving money. In middle age, you save so you can have a good retirement. But if you save muscle mass, you'll have an even better retirement," Dr. Williamson said.

W. Jack Rejeski, PhD, a behavioral scientist at Wake Forest, warned that difficulty climbing stairs can be the first sign of functional decline. "We've shown in our research that [such problems] are one of the first signs of early disability."

"The one thing people are most fearful of losing is the ability to function independently," said Tony Marsh, PhD, associate professor of exercise science at Wake Forest. "The strength of your muscles is fundamental in maintaining your independence."

Disease fighter

It's not only functional decline that becomes evident with muscle loss. The Centers for Disease Control and Prevention poses the question on its Web site: Why strength training? The agency provides a number of answers.

For example, arthritis pain was reduced by 43% after a group of older men and women completed a 16-week strength training program. Exercise was just as effective, if not more so, than medications, based on the CDC findings.

Strengthening exercises also can improve balance and flexibility, important in reducing the risk of falls and injury. And, the pull of muscle on bone also builds bone density and helps ward off osteoporosis, which is a major problem for post-menopausal women and older men.

There even is good news in glucose control. The CDC materials include a study of Hispanic men and women who demonstrated improved glucose control after 16 weeks of strength training. The results were comparable with those produced by medication.

In another study, weight training helped to lift depression as effectively as did medications. Why this response should occur is not yet known, but speculation centers on the increased self-confidence that people build as their strength improves. Or perhaps the strength training is producing helpful biochemical changes in their brains, the CDC suggests.

Given that muscles are major reservoirs for the body's supply of fuel in the form of amino acids, having more muscle also may mean having more fuel, said C. Jessie Jones, PhD, professor of kinesiology and health science at California State University, Fullerton, and co-director of the university's Center for Successful Aging. "When recovering from an illness, a person relies on amino acids. The less muscle tissue they have, the less of a reservoir there is."

Muscles' metabolic properties also play a role in improving glucose control. More collective muscle could help control the global diabetes epidemic. CDC figures show that in the U.S. alone, more than 14 million people have type 2 diabetes, a 300% increase over the past 40 years.

New guidance

Recent guidelines also underscore the need for muscle strength. The American College of Sports Medicine and the American Heart Assn., for instance, stressed muscle strength importance in last year's joint recommendations for physical activity in older adults.

In addition to 30 minutes a day of moderately intense aerobic activity five days each week, the organizations call for muscle strengthening activity using the major muscles of the body at least twice weekly.

The AHA published a separate statement last year that emphasizes resistance training's benefits for older people, especially women and those with certain heart conditions. These populations were highlighted because often they become unable to function independently.

"The purpose of the [AHA] update was to underscore the importance of the health benefits of resistance training," said Mark Williams, PhD, director of Cardiovascular Disease Prevention and Rehabilitation at the Creighton University School of Medicine in Nebraska.

"In addition, resistance training has now been reported to potentially positively impact body composition with increased muscle mass, and improve various metabolic factors such as blood lipids and blood sugar levels," he added. Williams led the team that wrote the AHA statement.

Several experts in exercise science point to the role physicians can play in persuading patients to get moving. "Research has shown that if a primary care physician is behind something, patients are more likely to respond," Bushman said.

Physicians also may intercede when patients are recovering from illness. "Just being in the hospital for a few days can dramatically affect muscle mass," Dr. Williamson said. "So physicians, in addition to thinking, 'I've successfully treated this person's heart failure or pneumonia,' need to be thinking, 'How can I help restore their muscle mass and function?' "

Assessing a patient's physical functioning should be part of an office visit, Rejeski said.

One way to conduct an assessment of lower extremity function is by the Short Physical Performance Battery, Rejeski said. It takes about 10 minutes to administer and tests balance, gait, strength and endurance. "It's a very simple test, but it has been shown in large studies to be predictive of decline in function."

Action then should be encouraged.

"The sooner you jump on any signs of decline, the better off you are," Rejeski noted. "As you get further down the slope of disability, it's more difficult to recover."

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ADDITIONAL INFORMATION

Use it or lose it

If your patients -- or you -- need strength training, here are some suggestions from the National Institute on Aging.

  • Do strength exercises for all major muscle groups at least twice per week. Don't do strength exercises for the same muscle group on any two days in a row.
  • Use a minimum amount of weight the first week, then add weight gradually. If out of shape, start with as little as one or two pounds, or no weight at all. The tissues that bind the structures of the body together need time to adapt to strength exercises. Beginning with weights that are too heavy can cause injury.
  • Gradually add a challenging amount of weight in order to continue the benefits from strength exercises. If muscles are not challenged, no benefit occurs.

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Exercise helps, even after muscle fibers start to go

John Faulkner, PhD, has spent his University of Michigan career studying skeletal muscles. Now a research professor of molecular and integrative physiology at the university's medical school, he has made good personal use of the findings he has gathered.

He's 83 and has two artificial knees. Yet he bikes 10 miles a day, plays tennis five days a week and lifts weights.

He also has a firm grasp of why muscle mass declines as the years go by. "That's the one element that is very, very clear. There is exceptionally good data that muscles lose the number of fibers present as we age."

Neurological loss is another factor that seems to be at work. Faulkner's research has focused more recently on the role played by motor units that send signals from the brain to the muscles.

It turns out that physical activity plays a role in strengthening motor units, too. "People who are sedentary not only lose the motor units and the fibers, but even those that are left don't work very well," he noted.

This loss begins to occur in the major weight-bearing muscles between ages 40 and 50. "From there it's a pretty linear decrease until the end of the road," he said.

But that's not the end of the story. Although muscle fibers can't be preserved, the ones that remain can be made more effective, Faulkner explained. The size of the fibers can be increased by lifting weights.

Aerobic activity also can boost performance by increasing the fibers' endurance so they won't tire as quickly.

This strengthening process has been shown to work. "Master athletes maintain a high level of fitness throughout their life span," Faulkner wrote in a study published last July in Clinical and Experimental Pharmacology and Physiology.

Although the performances of marathon runners and weight lifters decline after 40, well-designed and carefully administered training programs can provide dramatic evidence that age-associated atrophy, weakness and fatigue can be slowed, he wrote.

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External links

Exercise is Medicine Program, sponsored by the AMA and the American College of Sports Medicine (link)

"Exercise: A Guide from the National Institute on Aging," National Institute of Aging (link)

Centers for Disease Control and Prevention on the benefits of strength training for older adults (link)

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