Twenty minutes may seem like forever when sprinting 6.5 mph on the treadmill -- but is the fitness center time limit enough heart-pumping cardio to reap any benefits?

"Any amount of time doing physical activity is going to be beneficial," said Dr. Douglas Aukerman, assistant professor in the department of orthopedics and rehabilitation and sports medicine.

Although he personally recommends that people trying to maintain their fitness levels engage in at least 60 minutes of physical activity most days of the week, Aukerman said he believes the 20-minute limit can still allow students to reach their full fitness potential.

The amount exercise each day, Aukerman said, can be accumulated in short segments of activity that total 60 minutes. "It used to be that people had to do continuous exercise," Aukerman said. "But now you can just accumulate [physical activity] in little segments of 10 minutes or more."

Penn State's head strength and conditioning coach, Chip Harrison, said the time limit on cardio machines exists so that there can be more opportunities for people to use the more popular equipment, such as the treadmills and elliptical trainers.

Although Rachel Devine (junior-mathematics) faces the 20-minute limit everyday as she uses the treadmill, she said she doesn't let the rule put a cramp in her daily hour on the machine.

"Sometimes I just switch treadmills," Devine said. "But I think [the time limit] should be 30 minutes, because 20 minutes is ridiculous."

Harrison said a 20-minute limit was chosen rather than 30 minutes so that one extra person per hour could use a machine. "There are times when all the treadmills are being used, and because of the 20-minute rotations, others can get a chance," Harrison said.

Harrison said increasing the number of 20-minute rotations on the equipment will allow about 1,500 more people to use the machines daily.

Because of the added opportunities to use the machines, Harrison said, it's almost as if there were more pieces of equipment available.

"If we had 500 treadmills on campus we might not need to [implement a time limit]," Harrison said.

"But the fact is that there are more people that want to do certain activities than we have opportunities for," he added.

But the limit should not stop people from doing more than 20 minutes of aerobic exercise, Harrison said.

Some information suggests that more than one type of equipment should be used while doing aerobic exercise, Harrison said. Just as most people use multiple pieces of equipment when strength training, Harrison said, people should integrate multiple cardio machines into their workout routine.

"Most people are better off doing some impact and some non-impact exercise anyway to avoid an orthopedic issue," Harrison said.

"There's nothing wrong with moving onto a bike or rowing machine," he added.

Aukerman said it's important to balance the demand for the machines with getting adequate time on the machines.

"In [limiting use to 20 minutes], you're encouraging more physical fitness throughout the student population as a whole," Aukerman said. "But it's not harmful to limit to 20 minutes."