If you've found yourself wondering what's this thing called Lagree that's been blowing up your ClassPass search results, it is, according to Instagram, the workout that celebs including Alessandra Ambrosio and Vanessa Hudgens credit for their crazy, NBD physiques.

The high-intensity workout is also the Bay Area's hottest sweaty trend.

Founded by Sebastien Lagree, who touts his patented Hollywood-favorite workout as the best way to achieve "ninja"-like tight muscles, Lagree has made its way up north, now with seven independently owned Lagree-licensed studios teaching the method in the Bay Area.

The workout itself is brutal, but brief—under 40 to 50 minutes at most studios—designed for maximum effort in a minimum amount of time using a contraption called the Megaformer to work what feels like every single muscle, for the duration of each class. Similar to a Pilates reformer in its moveable carriage, the Megaformer is designed to throw your core off balance. Loaded springs create resistance, and straps secure you onto the platform for extremity work. It sounds torturous—and it is. Each class take place entirely on the Megaformer; there is not a moment of real, on the ground rest in Lagree.

Typical classes are 40 minutes at the East Bay's newest Megaformer studio, X-Core (244 Grand Ave, Oakland) and also at San Francisco's most prolific Lagree studio, Core 40 (multiple locations).

Every studio follows a sequence more or less developed by Lagree himself. Class starts with slow, heavy lower body work focusing on fatiguing one leg, with a series of lunges, squats and skaters, and then the next. You can't hide from or speed through the burn. Then, an upper body sequence follows a similar format, and class typically ends with an ab series including moves like the Catfish (a mini pike movement) and French Twist (a twisty pike movement) to fry every last abdominal muscle fiber. Studios and instructors vary in approach, but all Lagree classes aim for constant core-torching. The workout "combines strength, endurance, cardio, balance, flexibility and core training in every single move," says Lagree. // Also look for Lagree classes at Core Society Fitness, 4010 San Pablo Ave. (Emeryville), coresocietyfitness.com, and at Bold, 3167 College Ave. (Berkeley). beboldstudios.com; lagreefitnessstudio.com.