You know the feeling when you stretch a muscle? It feels great as you lengthen until you move closer to the end range of motion and it begins to feel extremely tight and even painful. It’s like an elastic band that doesn’t want to stretch any farther.
This is called the myotatic reflex, which is your body’s natural way of protecting your muscles from stretching too far. It’s possible to overcome this to an extent by slowly stretching and exhaling to decrease tension in the muscle.
However, a method called proprioceptive neuromuscular facilitation stretching—or PNF stretching for short—tricks your nervous system into relaxing the myotatic reflex, allowing your muscles to stretch farther than what’s achievable with a traditional style of stretching.
“Using our body’s own nervous system to trick it getting more range of motion or length in a tissue,” explains Dr. Matt Stevens, physical therapist and owner of Pure Physio (Strongsville, Ohio).
And it’s actually quite simple. All PNF stretching requires is that you stretch a muscle and then forcefully contract that muscle before stretching it again. As you move into the stretch after the contraction, you will magically be able to stretch further that you did before. This allows you to create more length in the muscle and receives a greater flexibility benefit from the stretch.
Here are two ways to use PNF stretching, which Stevens demonstrates in the video at the top of this article.
This type of PNF stretch is based on the concept of autogenic inhibition. By stretching the muscle and following with an isometric contraction of that muscle, it’s possible to reduce the activity (or tone) of that muscle and trick the myotatic reflex to allow for a more significant stretch.
How to: Stretch a muscle as far as you can—remember, it should never be painful—and hold the stretch for 10 seconds. Next, contract that muscle as forcefully as possible against an immovable object, such as your partner’s torso as demonstrated above with the hamstring stretch. Hold this for 5 seconds. Now move into a stretch—using your partner’s assistance if needed—which should be deeper than what you achieved before. Repeat the stretch-contraction sequence three times for each muscle.
Contract-Relax, Antagonist-Contract Stretch
Your body is wired so that two muscles cannot shorten at the same time—otherwise they would fight against each other, and you wouldn’t be able to move. So when you actively contract a muscle, your nervous system automatically sends a signal to the opposing muscle (or antagonist) that it needs to relax so your joint can move. This is called reciprocal inhibition.
This variation of PNF takes advantage of reciprocal inhibition. It resembles the Hold-Relax Stretch form but involves a forceful contraction of the opposing muscle of the one that you’re stretching to move deeper into the stretch.
How to: Stretch a muscle as far as you can—remember, it should never be painful—and hold the stretch for 10 seconds. Next, contract that muscle as forcefully as possible against an immovable object, such as your partner’s torso as demonstrated above with the hamstring stretch. Hold this for 5 seconds. Now use the opposing muscle to pull yourself back into the stretch. Again for the hamstring stretch, this would be your hip flexors. Your partner won’t need to provide as much assistance as the Hold-Relax technique, but can give an extra push and can help you maintain the stretch if needed. Repeat the sequence three times for each muscle.
This is the third type of PNF stretch, which isn’t shown in the video. It closely resembles the Hold-Relax Stretch but instead involves contracting the muscle through an active range of motion. So for the Hamstring Stretch, you’d stretch the muscle for 10 seconds and slowly lower your leg to the table. Now raise your leg back up to 90 degrees and have a partner move you into the next stretch.
One word of caution, PNF stretching is intense and has been shown to negatively impact strength and power when performed before a workout. So save PNF stretching for after a lift or game, or for when you have a day off.