Top 10 Workout DVDs of 2011

Fab Ab Tightener

Jillian Michaels 6 Week Six-Pack ($15, amazon.com)

What you'll need: a yoga mat, a 3- to 8-pound dumbbell

Calories burned:* 267 per 34-minute workout

Why we love it: Don't be fooled by the title: You're not cranking out sit-ups here. Michaels, America's favorite drill sergeant, makes sure "there isn't an unused second" during either of the two firm-and-burn circuits, which alternate between standing and on-the-floor exercises, cardio, and toning. Testers have "no doubt that if you did this DVD often, you would get results." Michaels keeps the focus on the core, whether she's cuing cardio, such as plank jacks and squat thrusts; strength moves, such as wood-chop lunges; or waist-cinching exercises on the mat. "This is perfect to whip out when a vacation looms and you're on a six-pack mission," a tester says.