The well-trodden grass under a green and white tent pitched on Demonstration field was getting muddy by Saturday afternoon.

But the rain that rolled over campus that morning wasn’t the challenge for the members of the Beta Sigma chapter of Phi Sigma Pi, who were constantly bobbing up and down from 3 p.m. Friday to 3 p.m. Saturday.

The wind was the real challenge.

“We had the tent blow down,” said chemical engineering senior Mike Romein, who’d logged about an hour on the national honor fraternity’s teeter-totter during the night. “We couldn’t stop teeter-tottering so we had to be creative to get the tent back up.”

Fraternity members kept their teeter-totter moving up and down for 24 hours straight during the weekend to benefit the Lansing Area Parents Respite Center. The center offers child care to parents who have children with disabilities.

The group raised nearly $2,000 for the charity during this year’s “teeter-totter-a-thon.” This is the fifth year of the event, and the second benefiting the Lansing area charity, said zoology senior Maika Symkowiak, who co-chairs the fraternity’s fund-raising committee.

Symkowiak, who had logged about five hours of ups and downs on the teeter-totter, spent a day working with the charity and said she was impressed by the program.

“The workers are really good with the kids and the way the workers handled them - just the degrees of handicaps the kids have, it’s so individualized,” she said. “The workers are able to help every one of them.”

Most of the fraternity’s 94 members and pledges, who were to be inducted Saturday night, spent time on the teeter-totter or stopped by to give support, members at the event said.

The action presents “quite a workout on your legs,” said zoology senior Kellie Putney, who also co-chairs the fund-raising committee.

“It got a little rough here,” she said while on the teeter-totter Saturday. “I went home to sleep for a while (during the night).

“When I got back two guys were on it for like an hour and a half and were like, ‘Please, get on this teeter-totter.’”

Putney had spent about three hours on the teeter-totter by noon Saturday, and like many other fraternity members, she had spent more time on the field with friends.

But she didn’t seem to mind the workout.

“Our theory isn’t we’re moving,” she said. “The world is jumping around us.”