Weight training increasingly important to women's health

Muscles and bones are not the things that most little girls are taught they are made of, but women who want to remain strong and independent throughout life had best give them the same serious attention they've begun to give their cardiovascular systems.

Along with activities that improve overall fitness, experts say, women need to craft a program that includes lifting weights and working on machines that strengthen the power of large and small muscles.


Without such strength training, the kind of intense aerobic activity that many fitness-conscious women pursue can actually decrease muscular strength, leaving one with a healthy heart and lungs but weak arms, legs, back and stomach muscles, according to new studies of runners.

A growing body of research also strongly suggests that many of the exercises that develop strong muscles also build healthy and dense bones, thus warding off osteoporosis, a thinning of bones that can lead to a stooped-over posture and fractures in later life. Osteoporosis affects an estimated 20 million Americans, mostly women, and causes an estimated 1.3 million fractures a year.


But women have shied away from such exercises because weight lifting has been associated with men and with women bodybuilders, many of whom develop masculine-looking physiques.

For that reason, those who advocate this type of exercise for women refer to it as strength or resistance training rather than weight lifting and emphasize that women who train for strength and fitness will not develop masculine bodies.

"They will not look like either men or like women bodybuilders," says Barbara Drinkwater, exercise physiologist at Pacific Medical Center in Seattle. "The difference between men and women in the size and the definition of muscle is related to differences in hormones.

"Also, women bodybuilders deliberately select exercises to increase muscle mass. They are working out five to six hours a day," she says. "And when you see the pictures, those women are contracting the muscles to make them look better. Unless they are on steroids, if you saw them in a relaxed pose they would not look that much different from a very fit woman."

Ms. Drinkwater is one of a growing number of experts on women and exercise who encourage resistance training, beginning in one's 20s and extending throughout life.

"Strength is extremely important and probably overlooked by most women," Ms. Drinkwater says. "As one gets older, it is one of the important keys to independence. It is also important for younger women who may face the need to do something that requires more strength than they have."

Mid-morning on a recent Friday, exercise trainer Mark La Ponte of Chicago's Downtown Sports Club has already put three women through their paces in training sessions starting at 6 a.m. His next two appointments also are with women.

"Weight lifting is very good for bone density as well as muscle strength because the bones adapt to the stress," Mr. La Ponte says. "But a lot of the women are afraid of the barbells. They have a fetish about gaining bulk. So we do resistance exercises that accomplish the same thing."


In 1990, based on new data, the American College of Sports Medicine added two strength workouts a week to its recommended three sessions of aerobic exercise as a minimum for healthy adults.

The strength workouts recommended by the college, the leading organization of sports researchers, include one set of eight to 12 repetitions of each of eight to 10 different exercises that work on the major muscle groups.

The number of repetitions is chosen so that the weights lifted or the resistance worked against are heavy enough to develop strength but light enough to allow enough repetitions to develop endurance.

Women who embark on such a strength-training program can expect a 25 to 30 percent increase in their strength and endurance over a six-month period, according to research reviewed by the college.

"You can gain muscle strength at any age, but the earlier you start and the more you do, the easier it will be to keep going," says Patty Freedson, associate professor in the department of exercise science at the University of Massachusetts at Amherst.

Recent studies show that the loss of strength that comes with aging can be as much from disuse as from normal loss of muscle tissue. Both men and women can retain muscular strength by using their muscles, both through exercise programs and by keeping active in daily life.


The hottest area of research into the potential benefits of resistance training is the growing evidence that some exercises that strengthen muscles also make bones more dense and thus less likely to fracture.

Bone loss can be slowed or reversed by a combination of exercise, calcium and estrogen, according to several studies. Because many women are concerned about the potential side effects of estrogen-replacement therapy, there is much interest in just how exercise works to prevent bone loss and how well it works.

It is thought that the stress from exercise stimulates the bone-formation cells to work more efficiently and keep pace with or surpass the destructive activity of the bone-removal cells.

"We are still not sure about the biochemistry involved," Ms. Freedson says. "What is believed is that when a muscle is put under tension, like it would be in a resistance exercise, the muscle pulls on the bone where the muscle is attached and strengthens the bone."

Research by the Human Nutrition Research Center at Tufts University in Boston suggests that calcium and exercise work independently to prevent bone loss and increase bone density, each working on a different part of the skeleton.