The former U.S. marines at this full-throttle boot camp will put you through a regime of stretching, circuit training, weight lifting, full-body muscle-building and running—both laps and up stairs. Each hour-long session also features a grueling obstacle course where you’ll hoist yourself over walls, jump hurdles, climb monkey bars and scurry up ropes like a true leatherneck. The barks from your instructors—not mean, but tough as hell—also contribute to the warfare vibe. Flexible class times (there are up to eight classes a day) at this midtown studio guarantee that you’ll be able to unleash your inner warrior no matter how busy you are. 212-967-7977, warriorfitnessbootcamp.com. Schedule varies; see website for details. Single class $60, three-class introductory package $60, 30-class package with three-month expiration $1,140, other packages available.