StudioMixx Body Sculpting System, Berlin

At Studiomixx, owner and trainer Shandi Rooney applies the principle of muscle confusion—adding variety to a workout’s exercises—to help her students avoid plateaus as they evolve through her intense, calorie-burning Mixx fitness classes. Her main class, Mixx, keeps muscles guessing and stimulated under the influence of Pilates, yoga, and calisthenic exercises. The studio's new TredMixx classes combine interval training on treadmills, including alternating speed and incline, with total-body sculpting that uses weights, bands, balls, and ballet barre. Rooney, who has trained with Bravo channel personal trainer Jackie Warner and The Biggest Loser’s Jillian Michaels, also offers a handful of spinoff classes such as Mixx Lite for less advanced students, CardioMixx, and Circuit Mixx, as well as grueling, detoxifying Xtreme Barre classes that can burn hundreds of calories per session, or one pile of freshly raked leaves.