At first glance, curling looks like it could have been invented by a bunch of drunk shuffleboard fans who got bored while ice fishing out on Lake Minnetonka.

One person chucks a 40-lb hunk of granite down a sheet of ice while two others push brooms in front of it, trying to make that ice just slippery enough for that hunk of granite to land on a bullseye—or knock the other team’s stones out of play.

We know: THRILLING.

And to be sure, there’s plenty of booze in curling culture, either during friendly competitions or after an afternoon on the ice.

So if your definition of “sport” involves burning more calories than you consume, then casual curling—like golf, bowling, and definitely darts—may not exactly move the needle for the uneducated observer.

But these days, Olympic-level curling takes some serious stones. In addition to the time spent practicing on the ice, Olympic curling athletes spend a lot of time in the weight room and doing cardio. USA Curling Head Athletic Trainer Brian McWilliams, who has been with the U.S. Olympic curling team for 12 years, admits that this wasn’t always the case.

“When I first went to the Olympics, there were a couple skips [team captains, who throw the last stones] at fifth-end breaks that were going out and having a smoke break,” McWilliams says. “I had come from a NFL and college football background, and it was completely shocking to me. But [curling] has evolved immensely. You can’t just go out and be a club curler and come in and get lucky and make it to the Olympics. It takes a lot of dedication, a lot of time.”

U.S. Olympic coach Phill Drobnick agrees: “Curling for many years was looked at as a beer-drinking, social activity. In 1998, when it was adopted by the Olympics, the game changed as we know it. It went through a similar transition as golf made when Tiger [Woods] hit the scene. Some of the golfers would have beer bellies, and now golfers are athletes and they all have a mental skills coach. If you don’t take it seriously, you’re not going to be able to compete.”

Curling: A primer

Curling’s roots date not back to Lake Minnetonka, but to sixteenth-century century Scotland. Two teams of four (mixed doubles, debuting this year, has two), take turns throwing a stone down a sheet of pebbled ice about 150 feet long and 15 feet wide. The goal is to get the stone inside the 12-ft. outer circle (called a “house”), and preferably closest to the circle in the middle of the house (called the “button”).

As with shuffleboard, curling strategy involves placing “guard” stones in front of the house, as well as knocking out opponents’ scoring stones or guards. And as with horseshoes, the team with the stones closest to the button scores a point for each stone in the house and closer to the button than the opponent’s best stone.

About the name: “Curling” means slowly rotating the stone upon release (like a curveball), and gives the thrower a chance to curve the stone around blocking stones. As for the sweeping: A team can intensify the curl by sweeping one side of the stone. The friction created by sweeping also affects the stone’s speed and distance. Using both speed and pressure, good sweepers can add at least 10 feet of distance to the stone, also called a “rock.”

That’s where workouts come in.

High-intensity interval sweeping

Yes, the thrower needs to be accurate, and strong enough to reach the house without the stone going out of bounds. But at the Olympic level, a team’s sweepers determine whether the stone ends up short of the house or in it and close to the button. (Broom pressure is so critical, in fact, that people have started developing training brooms to measure a sweeper’s force.)

Prior to competition season, the American curling team hits the gym six days a week, for two to three hours a day. Monday, Wednesday, and Friday are weight-room days (lots of squats, cleans, and deadlifts), while Tuesday, Thursday, and Saturday are dedicated to cardio. The athletes also spend a couple hours on the ice every day perfecting their throwing and sweeping technique.

The curling team’s cardio workouts are interval-based to simulate the sweeping in a match.

“We will do a lot of 20 (seconds) on and 40 off, or 30 and 30, or 40 and 20 to simulate sessions for the sweepers, to get them used to that high heart-rate cardio activity,” McWilliams said.

Because of the athletes’ different locations and schedules—they often can’t quit their day jobs—they will do workouts on their own, with those intervals involving running hills or time on the rowing machine, elliptical or treadmill.

Nutrition is also important, according to Drobnick. “The guys are working with a dietician and making sure to get they are getting the right proteins,” Drobnick says. “Some are doing shake supplements.”

Two stones lighter, a world of difference

The combination of workouts and proper nutrition has resulted in a 30-lb weight loss for the John Shuster, the team’s captain, or “skip,” who directs and calls the shots at the end of the ice sheet and who throws the final stones. Shuster was part of the bronze-medal 2006 Olympic team.

But the training hasn’t only been physical—changing the competitors’ mindsets, McWilliams says, was critical.

“People would always say, ‘I’m a curler,’” McWilliams says. “We stopped using the word ‘curler’ and used the word ‘athlete.’ Everything we did we said ‘athlete,’ to get them thinking they are athletes, and I think that helped with their mental focus.”

Drobnick feels good that the mental and physical conditioning of the team has them poised to succeed in Pyeongchang.

“The goal is to make the playoffs,” Drobnick says. “This is the best team we’ve ever sent to the Olympics. We are definitely hoping to get them on the medal stand. If we bring back a medal it will help grow the sport even more.”