Tone House

"Unleash your inner athlete" is the mantra of this Union Square studio, which boasts one of the city's hardest workouts. Dim red lighting and a dramatic soundtrack up the intensity during a class that focuses on explosive movements—think sprints, jumps and burpees. Tone House's most infamous torture device—uh, prop—is a resistance harness: Imagine running, but with 70ish pounds of resistance pulling you back. Makes that treadmill run seem like a 20-minute nap, huh? Price: Single-class $40, five-class pack $185, 20-class pack is $620, Rookie pass is two classes for $40.