Jillian Michaels' 6 Week SixPack

Two challenging programs that infuse short cardio bursts within the mostly-ab-focused toning. As Jillian says, "it burns overall body fat while also conditioning your core." The aerobic segments mix calisthenic classics like jumping jacks with cardio-speed floorwork (e.g. mountain climbers and "floor jacks"). The toning sections are also fast-paced. They include a huge variety of cross-body and multi-muscle exercises (e.g. chops with planks, rotations with lunges). No resting or wasted motions, even the between-move transitions are smooth and quick. Includes some easier modifications, but both programs are tough. Requires just one 3 to 10 lb. dumbbell (many moves are kettlebell-style)