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.