If you're looking for the fountain of youth, you might find it at the Spring Valley YMCA pool in Royersford, Pennsylvania. 

Meet Joanne Arnold. She's 89 years old and teaches nine classes a week at two different YMCAs. 

"It keeps me active. It gives me something to do," Arnold said.  

A former Naval Air reservist, Arnold has never been one to sit around, but fitness actually came into her life for a very practical reason. 

"I was born chubby, so as soon as I could exercise, I did. I went to calisthenics classes, I learned to ride a bicycle, I roller-skated," Arnold said. 

Now, she's eager to get her workouts in, knowing the work pays off. 

"I enjoy being with people, and if you're not physically fit, you're not able to engage in activities," Arnold said.

And to get to those activities, including singing in a chorus, Arnold drives a red convertible Mustang. 

"I just love red convertibles. I've had convertibles for years, and it's a 5.0. I don't race it, but I like the power under my feet," Arnold said with a laugh. 

This October, Arnold will celebrate 21 years teaching classes at the YMCA, and she said she's not planning to stop anytime soon. 

And her advice to anyone wanting to live well?

"Keep moving," she said. "Just keep moving, stay interested, stay active, stay social."