Bob Harper: Totally Ripped Core, $15, mytrainerbob.com
What you'll need: a pair of 3- to 5-pound dumbbells
Calories burned: 380 during a 48-minute routine, 65 during an 11-minute bonus*
The skinny: Testers loved the "fun mix of fast-paced core exercises," like weighted side crunches, and muffin-top-melting plyometric bursts from The Biggest Loser's master motivator. They also gave a thumbs-up to the on-screen countdown clock; it helped them push through the full routine, which made one reader "'good' sore every time I completed it." Finish with the stretchy bonus session, which includes trunk rotations and windmills.
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