Proprioceptive neuromuscular facilitation stretching is the most effective way to increase range of motion. Instead of merely letting your muscles stretch passively, you first contract the muscles and hold them tight before relaxation. This stimulates a reflex called autogenic inhibition, which causes further relaxation. By using this method, you can stretch your hip flexors and quadriceps to their limit, contract them and then relax them into a deeper stretch.
Lying Assisted Quadriceps Stretch
The PNF lying assisted quadriceps stretch targets the entire quadriceps group including the rectus femoris -- the main hip flexor muscle -- and the vastus lateralis, vastus medialias and vastas intermedialis muscles that also reside among the front of the thighs. The last three muscles only extend the knee. They do not participate in hip flexion. To perform this PNF stretch, you need a partner. Begin the stretch lying face down with your legs straight. Have your partner bend your right knee toward your buttocks and hold the point of discomfort for 10 seconds. Then, push against your partner's hands for six seconds to create a contraction in your quads. Relax and let your partner push your knee closer to your buttocks for 30 seconds. Repeat on the left leg.
Lying Assisted Hip Flexor Stretch
The PNF lying assisted hip flexor stretch is very similar to the assisted quadriceps stretch, but it emphasizes stretching more in the rectus femoris than the other quad muscles. A partner assists with this stretch as well. To begin, lie face down with your legs straight. Bend your right knee toward your glutes and let your partner lift your knee a couple of inches off the floor. Have your partner place one leg over your glutes and bend your knee into a passive stretch for 10 seconds. Then, push against his hands for six seconds and relax. Your partner pushes you into a deeper stretch and holds for 30 seconds. Repeat with the left leg.
Adductor Hip Flexor Assisted Stretch
The PNF side lying adductor hip flexor assisted stretch targets the hips flexors and hip adductor muscles of the inner thigh. A partner assists with this exercise too. To begin, lie on your left side and bend your left knee on the floor. Extend your right leg straight and let your partner lift to toward the ceiling until you feel a stretch, then hold for 10 seconds. Then, contract your quads by forcefully extending your knee and also press downwards to contract your inner thighs. Your partner resists by holding your leg in place. Hold the contraction for six seconds and then relax for 30 seconds as your partner raises your leg higher. Roll over and repeat on the other side.
PNF is deep muscle work and should be performed after a workout for the greatest benefits. If you are performing your PNF stretches on a non-workout day, always warm up with at least five minutes of aerobic activity and dynamic stretches like walking lunges. It's recommended to perform only one exercise per muscle group during a PNF session and to complete two to five sets of the chosen stretch. Wait two days before your next session.