Lunges

As sadistic as this may sound, I really love to kick my own ass.

My favorite way to induce the burn is a healthy set of lunges. Up, down, up, down. Weights, no weights, it doesn't matter. The point is to work the whole leg, and this exercise really packs a punch. And the ultimate? The "one legged lunge", also known as a single leg split squat. I usually do this bad boy on the Smith Machine. This guarantees an ass whoopin.

Have a comfortable pillow handy the next day, though.