PNF Basic Principle: "Appropriate Resistance"

This basic principle was formerly introduced by Maggie Knott as “Maximal Resistance,” but over the years her students, who continued on the legacy of PNF, realized therapists misunderstood Maggie’s intent and were completely misusing this basic principle.

They were literally applying their maximal resistance onto their patients, which was not therapeutic at all! So this principle is now called “APPROPRIATE resistance.”  There are 3 very important points to remember about this principle:

1.     Appropriate “resistance” can also be ASSISTANCE with the goal being to facilitate a smooth/coordinated effort from the patient throughout the desired range of motion.  This will promote AWARENESS, or as Gray Cook would say a “sensory experience,” of movement patterns in order to strengthen and improve the coordination of movement patterns.

2.     Resistance must be Facilitatory, NOT inhibitory: in other words too little or too much resistance can’t actually make the movement look worse. So we have to find their sweet spot.

3.     Using a variety of muscle contractions is necessary to restore normal function:

Let’s elaborate on this number 3 because it is a very interesting perspective and was quite a paradigm shift for me:

In the biomechanical/kinesiology model isotonic and isometric muscle contractions are defined by whether or not a muscle changes its length during a contraction or not:

Isotonic contraction - If the muscle is contracting and its length is changing.

Isometric contraction - If the muscle is contracting, but the length remains constant.


Maggie Knott provided us with a very insightful neurological perspective on isomeric and isotonic definitions:

She asked the question “Is the intent to move or not to move?” This gave the conversation a new dimension because the intent of the individual drastically changes how the brain calls upon their muscles for action.  

Think of it this way: if an athlete pushes on a wall with the intent to move the wall, would that be the same call to action from the brain to the muscle if that same athlete approached the wall without the intent to move it but just for the sake of eliciting a muscle contraction?  


Both are considered an isometric contraction according to biomechanical research definitions, but clinically the intent always matters, and making sure that our patients have the same intent as we do can make treatment flow a lot smoother.

With that said this is the way PNF would define contractions based on the question: What is the motoric intent?

a.     Isotonic (The intent of the patient is to move) :

 i.     concentric

ii.     eccentric

 iii.     Hold (stabilizing isotonic): the therapist or external object (a wall) prevents movement from a patient with the intent to move. (Manually this is more applicable in the neurological rehab setting where patients have a hard time understanding contracting muscles without actually moving; its either I move or I don’t move)

The verbal cue here might be “don’t let me move you” or “push against me”.


b.     Isometric: The intent of BOTH the patient and therapist is not to move but to just elicit a muscle contraction.  The verbal cue here can be “I want you to just meet my pressure and match my resistance.” This way it doesn’t become a “win or loose” match between the therapist and the client.

Keeping the intent in mind can work wonders during treatment or even when treatment planning. 

Going back to the first point of resistance can also be assistance sounds like a paradox, and if you are familiar with the 4x4 matrix that comes to us from the Functional Movement Systems this should make sense to you. If you are not familiar with the 4x4 matrix then I highly recommend you learn about it because it was a game changer for me in terms of regressing and progressing exercises. 

Ramez Antoun