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
that 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 24
calories 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."