Disclaimer: I am not a medical professional. This article is based on my personal experience and should not be taken as medical advice. Information on this website is not meant to replace the advice of a doctor or other trained medical expert. It is not to be used to cure, treat, diagnose or prevent any disease, illness or condition. Always consult your doctor before starting any exercise program.
About a year ago I found myself laying on my back in a crowd of yogis as our trainer aggressively pushed my right leg upwards towards my face. To my embarrassment at the time, it only went about halfway.
“How much do you want to bet me that I can get this leg to touch the floor by your head?” he asked.
I stammered, knowing it was impossible, but also fearing whatever tricks he had up his sleeve. Next, he asked me to engage all the muscles in my leg and press it towards him for five seconds. Then, as I released, he pushed again, gently. While my leg didn’t make it all the way to the floor, it went significantly further than the first time.
This trick is what physical therapists call Proprioceptive Neuromuscular Facilitation or PNF for short. While I ultimately didn’t take our trainer’s bet, and he didn’t get my leg quite to my head, this introduced me to one of the best-known ways to increase static-passive flexibility[i].
The Idea Behind PNF
PNF stretching increases range of motion by accomplishing three things[ii]. Firstly, it trains the stretch receptors in the muscle to accommodate a greater length (as all passive stretching does). Secondly, it fatigues the fast twitch muscle fibers, which reduces the amount of resistance they provide in the second stretch. Lastly, it activates the golgi tendon organ, which reduces the extent to which the muscle contracts (through the lengthening reaction). In short, PNF takes down a few of the shields that prevent the muscles from stretching, allowing practitioners to go deeper.
Three PNF Techniques
So how exactly do you use PNF stretching? There are actually several ways, but I’ll explain three commonly used techniques. While some PNF stretching can be done alone, it’s easiest to start with a partner to understand the process and effect. The three techniques[iii] I’ll explain are called the Hold-Relax Method (HR), the Contract-Relax Method (CR) and the Contract-Relax-Antagonist-Contract method (CRAC).
Hold-Relax Method (HR):
In the HR method, an individual first passively stretches the muscle being targeted. With the hamstrings, this would entail laying on your back, with your partner holding your leg at around a 90 degree angle (could be more or less depending on your level of flexibility). You don’t want to go too far in this initial stretch, just come to a place of ease while still feeling some tension. Hold this initial stretch for 10 to 15 seconds. From here, you will isometrically contract the hamstring muscle. This means that you’ll engage your hamstring and imagine you’re pushing against your partner's hands, however your partner will provide enough resistance to your leg that it doesn’t actually move. Hold this tension for 10 seconds. Next, relax the leg while your partner holds you in the same original stretch. This second time, you will be able to go a little deeper, however, refrain from going beyond an individual intensity of 6 out of 10. After holding this second stretch for 10 seconds, relax the leg down on the ground. Feel free to go through 2 or 3 rounds of this HR method stretching and make sure to do it with both sides!
Contract-Relax Method (CR):
The CR method looks almost identical to the HR method. However, instead of using an isometric contraction (not actually moving the leg), we’ll do an isotonic contraction (meaning the leg will move causing the muscle fibers to change length). To do this, follow the previous process from the HR method, however when you contract and engage the hamstring, your partner will allow the leg to slowly push itself down towards the floor, lowering for a count of 10 seconds. Afterwards, you can once again move into a deeper stretch.
Contract-Relax-Antagonist-Contract method (CRAC):
The CRAC method builds on these two previous techniques by adding a contraction of the antagonist (opposing muscle group) muscles in the final phase. To use this method, follow the CR approach, however in the final stretch, instead of relaxing all your muscles, contract the hip flexor to pull the leg in the same direction as it is being pushed by your partner.
While PNF can be a great tool to increase range of motion, as with any stretching it should also be undertaken with care[iv]. Practitioners should already have an advanced athletic practice and be sure they understand the correct movements (watching videos or speaking with physical therapist is also recommended). PNF should also only be performed on certain muscle groups with long kinetic chains (think hamstrings and glutes, NOT shoulders or neck). Lastly, PNF is only shown to increase range of motion after exercise, so it's best to avoid PNF before physical activity.
When performed safely and correctly, PNF can be a great tool for practitioners to increase range of motion in some difficult muscle groups. If you plan on exploring how PNF may benefit you reaching out to the yoga or physical therapy community for advice is a great first step in getting started!
References:
[i] Yutetsu, M. et al. (2013) Effects of Proprioceptive Neuromuscular Facilitation Stretching and Static Stretching on Maximal Voluntary Contraction. Journal of Strength and Conditioning Research, Volume 27 – Issue 1 – p 195–201.