Fitness Vocab: PNF
Capitalize on this scientific stretching method.
Consider this Furthermore series further education for fitness. Here, we help define the terms that all athletes should know.
DEFINITION: PNF stands for proprioceptive neuromuscular facilitation. To really make sense of this form of stretching, you first need to understand proprioception, the body’s subconscious ability to know exactly where it is and how it’s moving in space. (It’s the reason why you can touch the tip of your nose without looking in a mirror.)
Specialized sensors throughout the body measure inputs like stretch, pressure, and speed, and relay them to the brain. Then the brain responds by telling the muscles what to do, like contract or relax, and exactly how much.
“The nervous system is designed to promote movement by activating one group of muscles while relaxing or stretching another,” says Alex Zimmerman, CSCS, director of Equinox’s Tier X program. “For example, if you’re contracting your biceps during a curl, in order to flex the elbow, the triceps need to relax or stretch.” This occurs through a process called reciprocal inhibition, in which the nervous system tells one muscle to lengthen to accommodate an opposing muscle that’s contracting.
Proprioceptors also keep you from overstretching. Once the nervous system detects that a muscle has reached the end of its typical length, it shuts the muscle off so you can’t stretch it any more. So when you’re performing traditional static stretches (think: bend and hold), it’s actually your neurological system that determines how deep you can move into that stretch, he says.
PNF takes advantage of these reflexes to allow you to get a deeper stretch and potentially improve your range of motion more than you could through static stretching, according to Zimmerman.
“Research has shown that increases in range of motion can enhance performance and decrease the risk of injury,” he says, noting that it also increases body awareness. “When the body and the brain can’t relax through a range of motion, we go into a very protective state, which can result in torn or strained muscles or tendons.”
TO DO IT: Just like static stretching, PNF is best used immediately following exercise, rather than as part of a warm-up, he says. (When preparing for a workout, dynamic stretching is still the way to go.)
Traditional PNF involves a second person, either a trainer or exercise partner, to help you deepen the stretch. The technique includes three separate protocols: hold-relax, contract-relax, and hold-relax with agonist contraction. Here’s how each works, using the supine (lying) hamstrings stretch as an example.
1. Lie flat on your back with one leg in the air and have a partner press your raised leg toward your chest. You should feel a stretch in your hamstrings. They should hold you in this stretch for 10 seconds.
2. Next, have them apply more force to your leg while you resist the pressure just enough to keep your leg from moving. Hold this isometric push against each other for 5 to 7 seconds.
3. Lastly, stop resisting and relax your hamstrings so that your partner can stretch your leg slightly closer toward your chest than in the pre-stretch. Have them hold you in this stretch for 30 seconds. The stretch will deepen due to autogenic inhibition, or contraction of the hamstrings.
1. Complete step one above.
2. Next, press your leg against your partner’s hands just enough so your leg slowly lowers toward the floor over the course of 5 to 7 seconds.
3. Complete step three above. The stretch will deepen due to autogenic inhibition, or contraction of the hamstrings.
Hold-Relax with Agonist Contraction
1. Complete step one above.
2. Next, have your partner apply more force to your leg while you press your leg against your partner’s hands just enough to keep your leg from moving. Hold this isometric push against each other for 5 to 7 seconds.
3. Complete step three above. The stretch will deepen due to autogenic inhibition, or contraction of the hamstrings, as well as reciprocal inhibition, or contraction of the quadriceps.
You can also apply PNF to virtually any static stretch on your own. Simply move into a stretch, contract the muscle you’re trying to stretch by pressing against the floor or wall, and then ease further into that same stretch.