Scores of fitness fanatics flocked to the Malkin Athletic Center (MAC) yesterday, lining up for hours in their last chance to sign up for fall aerobics.

More than 600 people enrolled in classes, said Harvard's Recreation Director John E. Wentzell. Wentzell added that 120 people had been placed on waiting lists and that he did not know how many people had been turned away.

The line of people waiting to be placed in classes stretched up five flights of stairs and wrapped around the building, according to MAC officials and students.

Laura A. Rosenbury '92 arrived forty minutes early and stood in line for over an hour.

"Basically, aerobics will help decrease the stress of college life and help me balance my classes. It was worth standing in line for," Rosenbury said.

Heidi L. E. Henson, who works at the Office of Career Services, waited in line for nearly two hours. "I want to keep in shape and aerobics will force me to do that. Also, the classes are free."

All undergraduates, faculty, staff as well as those who purchase an athletic pass for the MAC are eligible to take the free classes.

Sheryl K. Sandberg '91 has been teaching aerobics for four years. "There are a lot of classes, but they fill up quickly because they are limited to 40 people," Sandberg said, adding that the enrollments were limited last year when engineers determined that more than 40 people in each class made the MAC structurally unsafe.

Still, the MAC is able to offer twelve classes each term. Wentzell reported that the number of classes offered is limited by the space available.

"If I had larger facilities, I know they would be filled," Wentzel said. "We continue to grow every year. People are more aware of fitness now and our program offers fun with a very talented staff."