Weights Build Muscles But Not The Manly Kind

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As any woman who has ventured into a health club knows, the weight-lifting area is very much a male domain. The rubber-surfaced nonslip floor where the barbells and dumbbells reside is dominated by hefty men, grunting and groaning as they pump iron. Most women steer clear, clustering instead in the group exercise classes, taking yoga or step aerobics. And that, medical experts say, can be a mistake, at least for women who want to reshape their bodies. While cardiovascular exercise like running can help the heart and burn calories, the best way for women to change their look is to lift weights - heavy weights.

"To really reshape yourself, you have to hypertrophy muscles," said Dr. William J. Kraemer, a professor of kinesiology at the University of Connecticut, referring to the medical term for muscle growth. Dr. Kraemer was the principal author of a new position paper on weight lifting for the American College of Sports Medicine and is the editor of a leading research journal on weight lifting, The Journal of Strength and Conditioning Research.

There are also health benefits, said Dr. Claude Bouchard, the director of the Pennington Biomedical Research Center at Louisiana State University. If men or women work sufficiently hard at weight training, the muscle they build is more efficient, with more mitochondria, which are the cell's energy factories. The muscle is also better at using fat for fuel and better at allowing people to use insulin to clear sugar from the blood, which reduces their susceptibility to diabetes

Studies also show that weight lifting can help with problems of aging. Investigators at the National Institute of Aging found that older people with osteoarthritis of the knee had less pain and improved mobility when they strengthened their leg muscles, working on those that support the knee. And, researchers say, weight lifting can stave off the sort of muscle wasting that forces older people to grab a chair handle for support when they rise. One problem that women face, however, is that they are hobbled by myths about weight lifting, expecting the wrong things and, sometimes, expecting too much, exercise physiologists say. The worst myth, these researchers stress, is that women who lift weights risk growing muscles like a man's.

Dr. Gary A. Dudley, an exercise physiologist at the University of Georgia and an author of the American College of Sports Medicine's statement on weight lifting, says he tries to dispel that notion by telling women to look around the gym at the women who are lifting heavy weights. "That's the simplest answer - just look around," he said. "There's a girl who works in my lab who does pull-ups like a yo-yo. She does not have 26-inch arms like Arnold used to have," he said, referring to Arnold Schwarzenegger. "They're just not there." Somehow, that message has not reached the general public, Dr. Kraemer said. Even his 22-year-old daughter believed it, asking Dr. Kraemer to help her and her friends by suggesting a program that would help them get fit without getting big.

Even women who are genetically capable of growing big muscles can never grow ones as large as a man's, Dr. Kraemer said. When researchers biopsied the muscles of female bodybuilders, who spend hours each day lifting weights, "They had smaller muscle fibers than the average male," Dr. Kraemer said. "And these were women who were taking drugs" to increase their muscle mass, he added. "A lot of women are just sitting there with a 10-pound weight," Dr. Kraemer said. "It's better than nothing, but they're really taking a second-class program. A lot of them are dramatically undercutting themselves." Even building bone requires that muscles be stressed, researchers say. They explain that bones have receptors that respond to demands on muscle, and weights can signal those receptors.

"Studies showed that stair climbing can help your bones - but the women wore weighted vests," Dr. Kraemer said. If the muscles-like-a-man myth discourages women from starting to lift heavy weights, other myths can discourage women from continuing, physiologists say. These are the myths that lead women to expect too much from resistance training and encourage them to give up when the benefits do not emerge. One problem is expecting immediate results. "It takes a lot of time to develop muscle," Dr. Kraemer said. "Most people want to have it happen in the first few months, but it takes three months or longer, usually three to six months," before a person looks much different, he added. Forget the idea of spot reducing, researchers say, like "toning" the muscles of the inner thighs, for example, and slimming them. "Spot reducing is not a real thing," Dr. Kraemer said. Many women also cling to a belief that is almost an act of faith among exercisers: muscle burns more calories than fat. Therefore weight lifting, by building muscle, will noticeably increase the body's metabolism. Sorry, said Dr. Bouchard, who is directing a national study on the genetic inheritance of an ability to train with aerobic exercises. He said that weight lifting had virtually no effect on resting metabolism. The reason is hat any added muscle is minuscule compared with the total amount of skeletal muscle in the body. And muscle actually has a very low metabolic rate when it is at rest, which is most of the time.

SKELETAL muscle, Dr. Bouchard said, burns about 13 calories per kilogram of body weight over 24 hours when a person is at rest. A typical man who weighs 70 kilograms, or 154 pounds, has about 28 kilograms of skeletal muscle. His muscles, when he is at rest, burn about 22 percent of the calories his body uses. The brain would use about the same number of calories, as would the liver, Dr. Bouchard said.
If the man lifts weights and gains 2 kilograms, or 4.4 pounds of muscle, his metabolic rate would increase by 24calories a day.

Dr. Jack Wilmore, an exercise physiologist at Texas A&M University, said that the average amount of muscle that men gained after lifting weights for 12 weeks was 2 kilograms, or about 4.4 pounds. Women, of course, will gain much less. A corollary to the hypothesis that you burn more calories simply by adding muscle is the belief that muscle can noticeably change your body weight. The idea is that when you do resistance training you may actually be thinner yet weigh the same or a little more, because muscle is heavier than fat. That holds a grain of truth, because muscle is more dense than fat. But, Dr. Bouchard said, the problem is that few people put on enough muscle in proportion to their total body mass to make a noticeable difference in their weight. The idea that you will weigh the same or more but you really are thinner may be true if you work hard at weight lifting for many months, but otherwise it is another myth.

But when it comes to weight lifting, researchers also confess that they have not answered some age-old questions. Why, for example, do muscles feel sore a day or two after they are stressed? One possibility is that they get damaged, with tiny tears ensuing from the work of lifting weights. But, said Prof. Stanley Salmons, a muscle researcher at the University of Liverpool, "damage and pain have different time courses, and they respond differently to repeated bouts of exercise." He added that delayed muscle soreness remained a mystery. "At this moment I do not know why muscles get sore, and no one else does either."

It is also unclear how to prevent soreness. "You hear trainers say it's very important to stretch before exercise," Dr. Salmons said. "But there were experiments in which people did exercise with or without stretching, and it didn't seem to make much difference." As for the techniques of weight lifting - how often, machines or free weights, in what order to do the exercises, how quickly to lift a weight, how long to wait between sets - the research is equivocal. But, Dr. Kraemer said, those are details that should not concern most people. Despite the fervent marketing of programs and the magical properties attributed to various regimens, there is little difference in the results of varying resistance training systems, he said. What matters is keeping the weights heavy enough to stress the muscles, exercising consistently and working every major muscle group. "Think of yourself as being on a continuum," Dr. Kraemer said. "At the beginning, when you are out of shape, just about anything can work."

 The New York Times    7/02 By GINA KOLATA