Zumba, step over. Spin class, put on the breaks. Indoor surfing is the hottest new craze to crash the workout scene.

The classes — experts say each session burns about 1,000 calories — are circled around the RipSurfer X. The machine was developed by former professional hockey player Mike Hartwick, CEO of SurfSET, who liked the way surfing toned his body. However, Hartwick was disappointed that he couldn’t get the same results through other fitness regimes.

“I would quickly bulk up and lose the lean and toned physique that surfing gave me, no other workout could compare,” Hartwick says on the company’s website. “Then it hit me. I’ll design a machine to mimic the workout that I got while surfing.”

Indoor surfing classes have been rolling into temporary fitness locations in various U.S. cities such as New York City and Los Angeles, and excitement about the new trend is growing. But the 45-minute class isn’t for everyone.

“It’s actually harder than surfing,” Sarah Ponn, co-founder and fitness director of SurfSET Fitness told Reuters. “Our primary goal is fitness. We burn a lot of calories. There’s a lot of paddling, a lot of standing on an unstable board. It’s very athletic,” she continued.

Like many fitness classes, there will be variations of indoor surfing offered to give almost everyone a chance to excel on the board.