Nearly everyone alive today has tried a hula hoop: The large, plastic rings filled with noise-making beads that first caught on the the 1950s. Some people are good at using them; most are not. Still, it’s a toy meant to provide a fun challenge and nothing more, until now: It would appear that hula hooping has been reborn as a fitness phenomena, allegedly capable of burning up to 600 calories per hour.

Shockingly, hula hoops have their origins in fitness, first fashioned by the ancient Greeks as a means of exercising the hips. Those involved in the industry say that keeping the hoop spinning isn’t as hard as it seems. When adults have trouble, its because they’re likely using children’s hoops, designed for much shorter people and far too small.

“You can’t hoop with a kid’s hoop. When you were a kid you were half as tall,” circus hooper Marawa Ibrahim told Reuters, adding that a hoop should reach to the hips, at least. “I used to teach a gym class of overweight women. I made hoops that were almost up to their armpits and they could do it.”

Kelly Strycker, director of Chicago Hoop Dance, told Reuters that hoop dancing is most popular among women aged 25 to 60. The class includes some elements of yoga, and is attractive to women who want an effective fitness routine that’s also fun enough to do again and again.

The American Council on Exercise found that hooping can burn as many as 600 calories per hour, due to the unnatural motion required to keep the hoop going. Mastery, they say, is an issue, but also noted that larger hoops reduce the learning curve yet deliver similar benefits.