If Zuzana's chiseled abs alone aren't enough to inspire you, then you'll love
Bodyrock.tv for their creative moves, basic equipment, and short but very intense workouts. The cardio and (mostly) bodyweight circuit workouts are easily adapted to any skill level. Bonus: Unlike many YouTube channels, Freddy shoots high-quality video and Zuzana is great at both explaining and demonstrating.
Video: 10 minutes to a flat stomach!
