Researchers at the School of Public Health are finding increasing evidence that popular myths regarding the hazards of exercise for women are dead wrong.

Associate Professor of Population Sciences Rose E. Frisch, in conjunction with the Harvard Population and Development Center, showed that contrary to popular belief, exercise does not lead to osteoporosis, nor does it indefinitely reduce fertility in women.

According to Director of Cross-Country and Track and Field Frank J. Haggerty, this research contradicts the "common assumption."

For example, it is widely believed that exercise adversely affects a woman's ability to carry a pregnancy. Frisch's studies proved this is false. Women who exercise have no more stillbirths or miscarriages than those who don't exercise, she said.

Frisch also disproved the common notion that excessive exercise makes women more susceptible to bone fractures and osteoporosis. The myth, Frisch says, first arose from other studies establishing a strong incidence of bone fractures in ballet dancers. Frisch says the correlation is probably due to the increased incidence of anorexia among dancers, not exercise.

Exercise Reduces Cancer

In fact, Frisch has shown that long-term moderate exercise reduces women's chances of getting cancer in the reproductive organs.

The study, conducted in 1985, included 5398 women aged 20 to 80, approximately half of whom had participated in college athletics.

Frisch discovered that women who had not exercised during college were twice as likely to get breast cancer as athletes, and two and a half times more likely to get cancer in the reproductive system.

Women who exercise are less afflicted by cancer than those who don't because their estrogen levels are lower.

Estrogen is a hormone that regulates the development of the female reproductive tract.

Frisch theorizes that women with high concentrations of estrogen must disperse the hormone, which may increase the likelihood of errors in cell division, leading to cancer.

Athletes React

Some Harvard athletes are not at all surprised by the research results.

"I've always known that it reduces the risk of cancer," said Genevieve A. Chelius '95, a soccer and lacrosse player for Harvard.

"I think there are so many multiple benefits from exercise that I am not surprised by that," Chelius said.

Other students were more skeptical of the findings.

"I've heard of some of the ideas," said Carrie P. Shumway '96, who plays field hockey and lacrosse.

"I know where they're coming from when they say that women [athletes] have problems with fertility," Shumway said. "I don't think it's a myth that there is a negative effect."

Frisch is now working in conjunction with Lecturer on Biostatistics in the School of Public Health Grace Wyshak on a study of endometriosis, a disease relating to the uterus, and is compiling a book detailing her research to date.

Delayed Menarche

Frisch showed that women who began exercising before menarche, the first menstrual period, on average did not have their first cycle until the age of 15. The normal age for menarche is 12.

According to Frisch, the delay occurs because the brain regulates the onset of menarche based on a woman's amount of body fat.

Lean women, including many athletes, have very little body fat, so a part of the brain called the hypothalamus represses the woman's menstrual cycle by keeping estrogen levels low.

If the woman's fat level drops below 22 percent of total body weight, the brain gets fooled into thinking the woman has not reached puberty and shuts off her cycle.

For example, women who are 5'5" or taller and weigh less than 108 pounds, Frisch said, were found to have no cycle because they were so lean.

Frisch explained that this process is easily reversible merely by the woman's gaining weight.

"Some athletes could turn cycles on and off with a three pound weight gain," she said.

"Sports and exercise can be related to low body fat," Shumway said, "And that can easily be fixed with your diet."

Frisch pointed out, though, that women who have been too thin and are gaining weight are advised to gain over the threshold in order to reactivate ovulation.

Women who are right on the threshold, Frisch said, will have their cycle, but they will not ovulate.

No Coke?

Surprisingly, though exercise does not make women more susceptible to bone fractures, it appears that drinking soda might do so.

In May of this year, Frisch and Wyshak conducted a study that showed that carbonated beverages, particularly cola drinks, make adolescent girls 12 to 17 years old more susceptible to obtaining bone fractures. There seemed to be no effect in boys.

Wyshak said that these results indicate that there must be a hormonal factor involved. But Wyshak said hormones are not the only cause of the increase in bone fractures.

"Very often people substitute [cola] for milk," Wyshak said.

From the results of her studies, Frisch concluded that long-term moderate exercise and cutting out carbonated beverages from the diet are of extreme benefit to women.

Frisch said that, ideally, women should do at least the equivalent of running two miles five days a week.

"If they haven't begun before, they should start," Frisch said.

Frisch said that this study provides very important information to women.

"It means that young women, for public health and their own health should begin moderate regular exercise early," Frisch said.

Frisch said that the results of the study are now being pursued in further studies.

"Other people are now pursuing how the brain knows how fat you are," Frisch said.

Wyshak said that other researchers are pursuing the results of their study now because most people were not interested in the study when it first came out.

"I think we were ahead of our time, so to speak," Wyshak said.Crimson File Photo