Abby Heiser, Kirsten Bornkessel and Liam Kilbreth stretch at Planet Fitness.

Teens ages 15-18 can work out for free this summer at Planet Fitness.

The Teen Summer Challenge is the chain's way of encouraging teens to exercise while they're out of school. 

You don't have to be a member or purchase anything for your kids to participate. However, if your child is under 18 you have to sign a waiver when they register. 

After that, they can go to the gym without you. 

To register, take your teen to any Planet Fitness location to fill out paperwork. Just keep in mind that they can only work out where they sign up. They won't be able to use other locations. 

Though the offer is not a competition, it's called a challenge to bring a call to action on teen health.

“At Planet Fitness, a healthy and active lifestyle should never be a challenge — which is why we’re flipping that notion on its head with the launch of the nationwide Teen Summer Challenge," said Chris Rondeau, Chief Executive Officer at Planet Fitness. "We want to give teens across the United States the chance to stay active when school is out — a time when they may not otherwise have access to organized fitness or athletic programs, which is why we’re offering a safe space to exercise for free and spend time with their friends all summer long.”

There are also prizes to be won.

By the end of summer 51 teens will be randomly selected to receive a $500 scholarship and one teen will get a $5,000 grand prize (they're automatically entered when they sign up). They can win prizes such as club swag, movie tickets and wireless headphones on the Planet Fitness IG and Twitter channels 

Angela Pittenger | This Is Tucson