Don't be fooled by its seemingly harmless name, this quad killer can wreak absolute havoc on your thighs if done at the right time. After squats, leg presses and lunges, you can finish off your quads with this extreme stretching movement. Standing upright, slowly lower yourself toward the floor letting your pelvis and knees move forward. At the bottom of the movement, your butt should almost touch your heels. Hold the stretched position for at least five seconds, then straighten your legs, flexing your quads at the top. Repeat this stretching sequence for 10 reps.