Lay face down on the floor with your partner kneeling beside you. Flex one knee and raise that leg off the ground, attempting to touch your glutes with your foot.
Have your partner kneel on your right side and place one hand on your lower back or glutes. His/her other hand should grasp your ankle or knee and push your shin toward your butt. You should feel a stretch in your quadriceps.
After 10 seconds, try to push foot back toward the ground against your partner's resistance and hold for 6 seconds.
Following this 6-second contraction, relax and allow your partner to stretch your quads for another 30 seconds. (If you want, try contracting your hamstrings for greater ROM gains.)