One of the best exercises for your butt and legs are lunges, and this variation takes the cake! Since you alternate directly from forward lunges to reverse lunges on the same leg, you'll really feel your thighs and glutes firing up. And no, you probably won't be walking normally tomorrow after doing this move, but that's a good thing, right?

• Stand with the feet together.
• Put weight in the left foot, lift your right knee up, and step into a forward lunge. The front knee should be at a 90-degree angle with the left knee just barely hovering above the ground.
• Push into your right heel, come to stand, and immediately step the right foot behind you into a reverse lunge with the left knee at a 90-degree angle.
• This counts as one rep.
• Without stopping, move through eight to 10 reps on this side and then repeat on the other side for another eight to 10.
• Shake out the legs and repeat for another set or two.