Here’s an idea that’ll knock you out: a gym with no class times.  At 9Round, a national kickboxing franchise, you show up whenever you want, put on your gloves and fight your way through a nine-station circuit. The 9Round location that opened this summer in Arlington has been such a smash that an additional four are coming to Northern Virginia. (And a D.C. location is in the works.)

What it is: “I’m not training you to be a fighter. But I’m training you like a fighter,” says Arlington franchisee Rob Graveline, a longtime trainer who’s coached folks including undefeated welterweight Todd Wilson. The duo teamed up to bring 9Round to the area, and they lend an air of authenticity to what resembles an old-school boxing gym.

You make your way around the room — dimly lit so no one feels “on display,” Graveline says — completing the exercises posted at each station, where you’ll spend three minutes before the buzzer goes off. That’s not a signal to slack. It’s time for a trainer to shout out something everyone must do for 30 seconds. After a burpee blast, jumping lunges or other heart-pumping moves, you rotate to the next station. The good news is you’re done in 30 minutes. The bad news is you don’t get a break.

Moves: There’s a new routine every day, but it always follows the same structure. Stations 1 and 2 are devoted to strength and endurance, and involve toys, such as jump ropes and medicine balls. Stations 3-8 are where you get to jab, hook, cross, shove and kick. You’ll contend with heavy bags and speed bags, as well as catching mitts that trainers hold while demanding various combos. The final station is dedicated to working your core. One recent selection: Hold plank position while jumping your feet in and out.

Workout: “I wear a headband every time because I sweat so much,” says Brad Byrd, 25, who’s been a member for two months. According to his heart rate monitor, he burns 450-500 calories in a half hour. But Graveline notes it’s up to each individual how much to do. A trainer is always on hand to correct form and suggest modifications, he explains, and if you really want to go through the circuit again, “I’m not going to get in your way.”

Crowd: “I’ve learned that women love to hit stuff,” Graveline says of his 75-percent female clientele. The appeal is in the atmosphere, says Sophia Peabody, 26, who came with no boxing experience. “The staff made it easy to ask questions and it’s all levels of fitness,” adds the Old Town resident, who’s dropped 20 pounds since joining the gym three months ago. Now — in true 9Round style — she’s ready to throw a punch anytime.

Details: Your first workout is free — with loaner gloves provided — at 9Round (2250 Clarendon Blvd., Arlington). Coming back? Buy your own hand wraps and gloves for $40, and you can drop in for $15 per class. Monthly memberships with unlimited classes are $79-$99.

You might also like: