Kettlebells plus Jillian Michaels equals pain. But there’s no doubt you’ll subtract pounds with the “Biggest Loser” trainer’s latest DVD, “Shred-It With Weights” ($9.99). The disc features two workouts (a beginner-friendly level 1 and an “Are-you-serious?” level 2) along with a handy kettlebell tutorial to prevent you from throwing out your back with the swinging, lifting and jumping. You can do the workout with a dumbbell, too, but it might feel clumsy.