What is a PNF stretch?

Today’s video will explore PNF stretching, including a detailed explanation of the protocol so you can deliver this type of stretching to your clients.

This is for you if you are a trainee/newly qualified FITPRO, or confused and overwhelmed about the PNF stretching protocol or how to use it with clients. You can follow along with the video to ensure you fully understand and can apply this to every client session.

Watch the 9-minute video to outline PNF stretching and the protocol, then test your knowledge with three mock questions.

Watch: What is a PNF stretch?

What is a PNF stretch?

What is Proprioceptive Neuromuscular Facilitation (PNF)?

PNF uses isometric muscle contractions and progressive stretching to develop the flexibility of a muscle. It is usually assisted by a trainer but can be performed directly by the client (depending on the muscle) if more appropriate.

The PNF protocol features 30 seconds (or more) of stretching to increase the length of the muscle, and then 10 secs of isometric contraction on the same muscle. This alternation between the contraction and relaxation creates confusion in two proprioceptors allowing significant improvements to muscle flexibility and joint range of movement.

Top 5 benefits of PNF stretching:

1. Rectify muscular imbalances and correct poor posture – which is exacerbated by sitting down a lot. Stretching commonly tight muscles (including the chest, hip flexors, hamstrings, adductors and low back) will help correct common postural deviations. A PT can analyse their client’s squat assessment to identify areas that are tight and then focus PNF stretches towards these to help correct their compensations.

 2. To improve flexibility and avoid back pain. The lower back, hip flexors, and hamstrings are commonly tight, which can cause mild cramping feeling and “knots” inside the muscle.

This results in a downward spiral of poor blood flow, cramping, pain, and tightness. Stretching these regularly to help avoid lower back pain.

3. To avoid injury – by taking the muscle through increased ROM whilst controlled, your client is less likely to get injured by sudden movements or their exercise programme.

4. To improve performance – Regular analysis and observation of how a client moves, will allow you to see areas that hinder client performance. Regular flexibility training can help to improve performance considerably. Stretching a muscle to the full range will “switch off” the muscle. Therefore, stretching the Antagonist of the targeted muscle during a warm-up could encourage activation of the targeted muscles in your workout – for example, try stretching the hip flexors before a squat or running session – to really improve glute activation.

5. Reduce DOMS symptoms – Stretching realigns the muscle fibres and can aid recovery following an intense training session. Include PNF stretches as a part of a cool-down whilst the client is red hot, and this can help mitigate the symptoms associated with Delayed Onset Muscle Soreness (DOMS), in particular swelling, inflammation and aches.

What happens to the muscle when we stretch?

We know why every client should stretch, but what happens physiologically when we stretch?

The muscle attaches to a bone via a tendon having crossed a joint;

a muscle contracts and pulls on the bone which now changes the angle of the joint. 

If the muscle is tight, it’s constantly shortened and therefore pulling on the bone which physically limits ROM at the joint. 

In contrast, if the muscle is weak or inactive, the joint is heavily compromised and ROM can be excessive. 

Within the Tendon there are Golgi Tendon Organs (GTO’s) and within the muscle, there are muscle spindles. 

These two influence flexibility and stretching because of the reflex actions that they stimulate. 

Let’s dig a little deeper >>

What is a Muscle Spindle?

Muscle spindles are located within muscle fibres and their main function is to send messages back from the muscle to the central nervous system to inform about its state of stretch (length of the muscle). 

If the muscle is stretched, distortion of the muscle spindles causes a ‘myotatic reflex’ (automatic contraction) to come into play, thus avoiding damage through overstretching or miss-use of the muscle. 

This muscle spindle activation (muscle contraction) is the “pull” felt during a stretch. 

The amount and rate of contraction elicited from the stretch reflex are proportional to the amount and rate of stretching.  Hence, the faster and more forceful the stretch, the faster and more forceful the reflex contraction of the stretched muscle; therefore, the greater the likelihood of the muscle tearing (particularly in an untrained muscle).

The role of a muscle spindle is to prevent injury by alerting to an over-stretched muscle. However, this can limit the development possible in one stretch; which is why we can use a PNF stretch protocol to override the muscle spindle and allow greater progression.

What is a Golgi Tendon Organ?

GTOs are proprioceptors located near the musculotendinous junction ( where muscles and tendons join). 

They are activated by a contraction in a muscle and help prevent excessive tension occurring within the muscle, or the tendon of that muscle. 

In contrast to the muscle spindles, stimulation of the GTOs will cause a reflex contraction of that muscle (the inverse stretch reflex).  This resulting relaxation is important for certain stretches because the inhibition of the muscle in which they are located will allow muscle fibres to lengthen and stretch further.

The relaxation occurs in the same muscle because of GTO activation called autogenic inhibition. 

This is achieved by contracting a muscle immediately before passively stretching it.  The contraction will increase GTO activation, thus increasing the subsequent muscle relaxation during the stretch.  Reciprocal inhibition is the relaxing effect that occurs in a muscle when the antagonist is contracting. 

This occurs to allow an easier contraction of the antagonist.  Hence, contracting the antagonist’s muscle will allow for a greater stretch in the muscle being elongated.

How to do a PNF stretch?

PNF stretching usually involves a 10-second isometric contraction phase followed by a 30-second relaxation phase, typically repeated three times. You can also see this in the video above.

Check out our lying hamstring PNF example >>


  • Your client must be thoroughly warm first, it is ideal at the end of a cool down.
  • Instruct your client to lie on the floor or mat.
  • Kneel beside the client and extend the client’s leg upward. Position the back of the client’s lower leg on your nearest shoulder.
  • Hold the client’s foot and just below the above the knee.  Your client’s resting leg can be straight or bent here, and arms spread to the side so they are evenly positioned and can push through the floor.
  • Make sure your back is kept neutral.


  • Your client should feel a stretch and have a totally straight leg.
  • Hold here for 30 seconds or until tension fades.
  • Ask your client to push against your shoulder with approximately 40-70% of their strength, using their hamstrings isometrically.  
  • Hold this isometric contraction for 10seconds and then ask them to relax.
  • As they relax gently push your participant’s leg in the direction of their chest, to increase the stretch.
  • Hold this stretch for another 30secs or until tension fades, then repeat the contraction and relaxation phases for 3-4 intervals.
  • Every stretch phase should increase the range of movement gradually.
  • Once the intervals have been completed, shake out your client’s leg and remember to do the same on the other leg.

PNF stretching is a great way to develop flexibility and you will see immediate and long-lasting results with your clients. Make sure you monitor intensity throughout and only do PNF once fully warm

Test your knowledge with 3 stretching Mock Questions

Look at the 3 stretching Mock questions below and jot down your answer on scrap paper or as a note on your phone.

Then scroll down to reveal the answers.

[NOTE: The answers are below the 3rd question]

1. Which proprioceptor senses length in the muscle?
A. Golgi Tendon Organ
B. Muscle Spindle
C. Actin and Myosin
D. Baroreceptors

2. What does the acronym PNF stand for?
A. Peripheral Nerve Firing
B. Propriocetive Neural Familiarisation
C. Painful Neural Facilitation
D. Proprioceptive Neuromuscular Facilitation

3. What is NOT a benefit of regular flexibility work?
A. Lower risk of injury
B. Improved performance
C. Tighter muscles around a joint
D. Correction of postural compensations

What’s the CORRECT answer?

Answers to the mock questions are :

Question 1= B, Question 2 = D, Question 3 = C

If you want more mock questions like this, then you can download more Free Mock Questions: DOWNLOAD NOW

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Hayley “What is a PNF stretch?” Bergman

Parallel Coaching

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