This pre-school gymnastics class at LTD Academy helps strengthen those muscles.
As Merryn's mom Christi Charles explains, "Having muscle tone will actually help keep your joints and give you less pain."
Christi and the other moms watching their little gymnsts all agree.
Christi's mom says, "It's good for your health in so many ways."
Their instructor Nick Finochio is a gymnast himself that also started young.
"It's good to start them young because their muscles are ready for whatever comes next."
For this age group, an obstacle course with swings, climbing and tumbling is part of the program.
As Nick explains, "I feel like it develops you better as a gymnast. I started young and it was easier to start young."
Merryn explains it best. "Because it's very fun."
For more information about the Pre-school gymnastics program at LTD Academy in Altoona, head here.