It used to be the gym was an adults-only zone. But as the rate of childhood obesity continues to climb, more and more gym owners are lowering their age minimum to accommodate kids as young as ten or eleven. It’s becoming increasingly common to see teens, or even tweens, on treadmills or elliptical machines, working up a sweat while watching Sponge Bob Square Pants or listening to the latest Jonas Brothers hit.

But some child development researchers are questioning the practice. Most gyms and health clubs are designed with adults in mind. Children’s growing bodies, specifically the open growth plates in their bones, make them more susceptible to injury. These experts also say kids should get their exercise by playing outside with their friends… not cooped up inside a gym.

Still, many pediatricians and fitness gurus are voicing support. They say gym workouts are a healthy opportunity for parent and child togetherness. However, they stress that gym time should supplement play time, not replace it. They also say children need proper training and adult supervision to avoid injury.

These experts offer words of wisdom. Be sure to keep a close eye on your children at the gym and adjust the equipment to fit their small bodies. Keep them hydrated with plenty of water. If they choose to engage in strength training, limit them to extremely light weights, especially at first. And lastly, don’t turn exercise into a chore. If a child isn’t having fun, it’s just not worth it.