Forza
Who says swordplay can't be fun?

Origin: Martial artist Ilaria Montagnani patterned the workout after iaido, an ancient Japanese swordfighting technique.
Who's Doing It: Athletes of both genders who had Uma envy after seeing the katana-happy actress in Kill Bill
The Workout: Wield a one-to-two-pound, three-foot-long wooden sword in an arm-strengthening, high-energy workout that will please anyone who's ever yawned at tai chi. Though it debuted in the late nineties, Forza got popular only after folks saw the sexy blade work of Quentin Tarantino's film (for which cast members took private sword lessons in L.A.). Before classes, an instructor shows beginners the basics: the grip and the stance (knees bent at all times). Then she cues the Asian-tinged techno soundtrack and you go to work. At the beginning of the hourlong regimen, you perform single cuts: up, down, and diagonal. Then moves are sequenced into precise combinations and performed nonstop during four-to-five-minute intervals. The goal is to maintain quick, crisp strokes and correct form, even as the one-pound sword begins to feel like 20.
They Say: Forza is great for building strong, low-bulk muscles in the arms, shoulders, abs, and back.
I Say: After an hour, your forearms and shoulders will burn as if you're a 5.9 climber who just scaled a 5.10. And the rush of wielding a samurai sword—even a wooden one—beats holding a dumbbell.
Where to Find It: In New York at the Reebok Sports Club/NY (thesportsclubla.com; classes free with membership) and Equinox clubs (equinoxfitness.com; classes free with membership). An instructional DVD, released in September, runs $30 (powerstrike.com).