Proprioceptive neuromuscular facilitation (PNF) is probably one of the fanciest phrases I use on a semi-regular basis. I sound really smart when I say it. Plus, it is a technique that works. Not that other techniques don’t, but the visible and more immediate results from performing a PNF are pretty impressive.
Research has shown an increase in range of motion and extensibility with consistent use of this handy tool. The question is . . . why? Well, there is a lot going on when we engage our clients in a PNF, but let’s get the nitty gritty out of the way first and break down the step-by-step process.
There is, as you might have already discovered, a lot of conflicting information out there about this tricky maneuver, and sorting through it might serve to be futile, as you can find articles supporting pretty much whatever position you hold. But collecting data has at least revealed that the general idea behind how to perform a PNF holds a collective truth: When a muscle is engaged and then relaxes again, it relaxes beyond its normal state, and this is information we can use to our advantage.

Two Basic Forms

For the purposes of this article, I am looking at the two most basic forms of this maneuver—the standard PNF (sometimes called contract/relax or hold/relax) and reciprocal inhibition (RI).

Standard PNF

The standard proprioceptive neuromuscular facilitation (PNF) looks something like this:
1. The therapist passively moves a muscle into a slightly lengthened position.
2. The client is asked to contract that muscle against resistance provided by the therapist.
3. The client holds the isometric contraction for a set amount of time (usually somewhere between five and 10 seconds).
4. Upon relaxation, the therapist pushes the muscle into a passive stretch beyond its original state.
5. Repeat this cycle three or four times.

Standard RI

The standard reciprocal inhibition (RI) looks something like this:
1. A therapist passively moves a muscle into a slightly lengthened position (sound familiar?).
2. The therapist then asks the client to engage that muscle’s antagonist to contract against resistance.
3. The client holds that contraction for a set amount of time (sound familiar again?).
4. Upon relaxation, the therapist passively stretches the agonist (the originally targeted muscle) beyond its normal state.
5. Rinse and repeat.
You get the idea. A muscle is targeted, and that muscle is asked to contract (in a PNF) or its antagonist is asked to contract (in an RI). The muscle is then stretched, increasing its extensibility and, hence, increasing the client’s range of motion. It’s a beautiful technique. But why does it work?

Why PNF Works

There are four physiological mechanisms at play that are largely looked at in research articles around this topic. They are wordy, complex, and, if read without the assistance of a strong cup of coffee and a good night’s sleep, can make your head spin. The mechanisms I am referring to are autogenic inhibition, reciprocal inhibition, stress relaxation, and the gate control theory. I know, I know . . . one of the mechanisms shares the same name as the actual technique. You can start to see how these articles can be frustrating.
Let me shift your attention away from the perplexing and toward Occam’s razor (the idea that when presented with a handful of solutions to a problem, the simplest one is the most likely answer). In this case, the answer might be an idea not often explored in analytical investigations. There are dozens of scientific theories as to how a PNF will recruit more muscle fibers, activate myelinated neurons in the dorsal horn of the spinal cord, and decrease nociception. But none of these are simple.
A broader perspective might offer some insight—and might actually be a lot easier to comprehend. Instead of directing our focus on recruiting more muscle fibers, let us instead acknowledge the possibility of recruiting more neurons. When a PNF is used in a session, perhaps the reason for its undeniable success is the mere fact that drawing a person’s awareness toward their physiological capabilities calls into action a series of neurological responses that shift how the tissues act. In other words, given that most people operate on autopilot, a focused attention combined with isolated movements offers the client an improved internal communication. Movement, and more importantly command of movement, then becomes easier. In turn, this increases self-awareness, which (as we all know) is the first step toward healing.
Perception is a funny thing. We can be in a certain frame of mind and have no idea how it might be limiting us. There is, indeed, a lot of science to back up why PNFs are the key to so much success in tissue health, but the psychology of healing is much more fascinating. Shifting awareness can open doors that we did not even know were closed. Now you’ve got a new key. Go ahead. Open a few doors.

Every time you are tempted to react in the same old way, ask if you want to be a prisoner of the past or a pioneer of the future.
—Deepak Chopra

Resources

• Dilek, Banu et al. “Efficacy of Proprioceptive Exercises in Patients with Subacromial Impingement Syndrome.” American Journal of Physical Medicine & Rehabilitation 95, no. 3 (March 2016): 169–82. https://doi.org/10.1097/PHM.0000000000000327.
• Hindle, Kayla B. et al. “Proprioceptive Neuromuscular Facilitation (PNF): Its Mechanisms and Effects on Range of Motion and Muscular Function.” Journal of Human Kinetics (March 31, 2012): 105–13. https://doi.org/10.2478/v10078-012-0011-y.
• Lucas, Ranna C. and Robert Koslow. “Comparative Study of Static, Dynamic, and Proprioceptive Neuromuscular Facilitation Stretching Techniques on Flexibility.” SAGE Journals 58, no. 2 (1984): 615–8. https://doi.org/10.2466/pms.1984.58.2.615.
• Papadimitriou, Konstantinos et al. “Effects of Proprioceptive Neuromuscular Facilitation (PNF) on Swimmers Leg Mobility and Performance.” Journal of Physical Education and Sport 17, no. 2 (2017): 663–8. https://doi.org/10.7752/jpes.2017.02099.