PNF Stretching is one of the most effective, yet often overlooked, training techniques that coaches can employ to enhance flexibility.
For being recognized as an essential pillar of strength and conditioning, flexibility seems to lack the same attention and interest generated by other physical qualities that are developed through training. For example, look no further than the world 
of strength and conditioning on social media. You’ll be much more inclined to find strength coaches showcasing impressive feats of strength, power, speed or even balance. How often do you see coaches talking about amazing flexibility routines?
It isn’t the fact that coaches don’t see value in increasing an athlete’s flexibility, it’s more to the effect that there are so many other athletic qualities that garner the spotlight, and thus have a higher emphasis within a training program. Luckily for us there are ways to improve flexibility that happen almost organically. Static stretching is universally known by athletes of all ages, and is typically found in some regard in any warm-up or cool down. A well-rounded strength training program featuring exercises performed throughout a full range of motion will even increase joint flexibility. However with flexibility, as well as other training effects like strength, power, speed, etc, in order to improve and display lasting effects, there needs to be a direct training stimulus occurring regularly.
So how can a coach utilize their allotted time with an athlete effectively and work to improve flexibility beyond simply static stretching at the end of a workout? Three letters: PNF.
What is PNF and how does it work?
Proprioceptive Neuromuscular Facilitation, or PNF, is a stretching technique that is used to improve muscle elasticity, and thus increase flexibility. For years PNF primarily existed in clinical settings, utilized by therapists to restore or increase joint range of motion in patients who were going through rehabilitation. Currently it has gained a lot of traction and is practiced within athletic and even therapeutic settings. The reason why it has gained popularity and should be included in a coach’s repertoire? It works. Research supports its effectiveness in increasing joint ROM.
While research has been conducted on PNF and its possible effectiveness for decades, it is still ongoing to determine what the exact mechanisms behind this form of stretching are. Four theoretical physiological mechanisms for increasing range of motion exist. They are: autogenic inhibition, reciprocal inhibition, stress relaxation, and the gate control theory. These four mechanisms are reflexes that occur when the golgi tendon organs in the tendons of the agonist or antagonist muscle detect harmful stimuli. Between them, these four theoretical mechanisms likely define why increases in joint range of motion are seen when using PNF.
There are two methods of PNF that are typically the focal points of any research on the topic. These two methods are also most commonly practiced in the athletic, clinical and therapeutic realms. They are known as the “contract-relax method” (CR) and the “contract-relax-agonist-contract method” (CRAC).
Contract-Relax Method (CR):
1. The target muscle is stretched and held passively
2. An isometric contraction of the target muscle is subsequently held for an allotted time
3. The target muscle relaxes and is re-stretched passively.
Contract-Relax-Antagonist-Contract Method (CRAC):
1. The target muscle is stretched and held passively
2. An isometric contraction of the target muscle is subsequently held for an allotted time
3. The antagonist of the target muscle is subsequently contracted while the target muscle is passively stretched
When performed regularly, PNF has been shown to have a positive effect on active and passive range of motions. This occurs by increasing the length of the muscle while also increasing neuromuscular efficiency. These results can be seen in healthy individuals, but also in those going through a rehab program to regain strength and ROM after sustaining soft tissue damage.
PNF Guidelines
The manner in which PNF is performed greatly dictates the results yielded. Just like any training program or exercise prescription, there are guidelines to follow that will enhance results and prevent any decrements in performance.
When to Perform PNF
Studies have shown that in order to increase muscular performance, PNF needs to be performed after exercise, or without exercise. However, when completed prior to exercise, doing a bout of PNF stretching will actually decrease performance in maximal effort exercises. Therefore, PNF is best utilized when placed directly after a lifting/conditioning session, post practice, during an athlete’s downtime (ie. Before bed) or on a true rest day. The research states that it is in the athlete and coach’s best interest to avoid using PNF in any capacity before a game, practice, lift, or conditioning session. When performed before any of these events, there is evidence of decreased performance in anything where maximal muscular effort is required, such as during sprinting, plyometrics, weight lifting, etc.
How to Perform PNF
Just like resistance training, results from PNF stretching can differ depending upon how it’s administered. While the passive stretch will differ depending upon the flexibility levels of each individual, it is important to give guidance on how much of an isometric contraction is given, as well as the duration of each stretch and contraction. The isometric contraction given by the individual being stretched can be 100% maximal, however if this is the case the athlete must be aware that muscles soreness and a potential contraction induced injury is possible. Giving a high, yet sub-maximal effort is recommended. In a healthy individual around 80-90% effort will suffice, and with an injured individual the contraction needs to be more individualized based upon nature of the injury as well as pain tolerance.
The typical time spent passively stretching an athlete when using PNF will range from about 6-10 seconds, where as the muscle contraction can produce effects when held anywhere from 3-10 seconds. The literature states that 6 seconds is preferred and will yield the appropriate response. Consistency and simplicity with athletes is crucial, so whatever time frame parameters are chosen need to be kept and utilized. As far as how many repetitions or bouts of PNF per muscle group are recommended will depend upon the individual, yet three seems to be an effective and appropriate number. After three repetitions, the ROM that is “unlocked” decreases significantly and the athlete has reached their so called finish. This ROM can improve but each rep seems to access around 15-20% increases in ROM and those increases just simply cannot keep occurring after each rep.
There will be varied affects when performing PNF, and while many stem from controllable variables such as the intensity and timing of the contractions and stretches, some changes in ROM will also depend on biological age, training age, and gender. The best results will come from a properly administered protocol that occurs several times a week.
Where to Perform PNF
PNF can be used on many muscle groups, however some remain easier to administer than others. As mentioned simplicity is key and it’s crucial to remember that majority of strength and conditioning professionals are not therapists. Majority of the following don’t require additional set-up, however if access to a massage/therapy table or anything to elevate the athlete off of the ground may make some muscle groups, like the hip flexors, more accessible.
Common Muscle Groups
• Hamstrings
• Quadriceps
• Hip Flexors
• Hip External Rotators
• Hip Internal Rotators
• Calf muscles
• Shoulder External Rotators
• Shoulder Internal Rotators
• Lat/Upper Back
• Chest Muscles
Joe Powell is an Assistant Strength & Conditioning Coach at Utah State University. He formerly held a similar position at Central Michigan University where he also taught classes in the Department of Health and Human Performance. Joe is a regular contributor to the IYCA Insiders program and has been a huge part of bringing the Behind the Science series to the IYCA. He is also the author of the IYCA Guide to Manual Resistance Strength Training. Get more of Joe’s contributions in the IYCA Insiders membership.
