Fitness enthusiasts have discovered what surfers have known for some time: the Indo Board trainer is a fun way to work on your balance and strengthen your core when you’re not near the ocean. This board-and-roller combo is now moving out of surf shops and into stores far from the shore. It’s also sold online on the company’s site and elsewhere.

To picture how the board works, visualize a flat surfboard on top of a rolling cylinder. You stand on the board and try to balance so the board doesn’t touch the ground. There’s also a cushion to use instead of the roller. Once you’re balanced, try to stay in alignment while doing a variety of exercises. Sound easy? It’s not, which is what makes it a good workout.

The idea is to use your abdominal muscles to maintain control of your body. This concept of core training has spawned a number of exercise accessories — the Balance Board and yoga balls among others — but few have unified balancing with the fun of surfing and other boarding sports.

Team Max tested an Indo Board and found it tough to master, but thrilling. Getting the board to balance on the roller takes patience and concentration. Once it balances, keeping the board airborne atop the roller is nearly impossible. It’s easy to see how getting it right could become a fitness addiction.

The top-of-the-line offering is the Indo Pro Training Pack ($324.95), which includes a large roller, a cushion, and a board long enough for a 6-foot-tall person. The boards come in a variety of sizes as well as designs, from natural to retro surf scenes.

Balance is essential not just for surfing, snowboarding, and skateboarding, but also for personal training of all kinds. It’s integral to the latest fitness crazes, like spinning, boxing, and CrossFit.  You can work out like a pro: the U.S. surf team is already using Indo Boards, the company says.