PNF stretching is a type of contract-relax stretching. Proprioceptive neuromuscular facilitation (PNF) is an abbreviation for proprioceptive neuromuscular facilitation. What exactly does that imply? It means that the stretching response is aided by innate reflexes. To perform contract-relax stretching, isometrically contract the opposing muscle first. Then, after contracting, try to stretch the intended target point further. For example, you could isometrically contract your triceps (opposite the biceps) for 10 seconds. Then you’d relax your triceps and straighten your arm to try to stretch your biceps even further. Stretching like this can be done on any muscle that has an antagonist.
What does contract-relax stretching mean in terms of neurophysiology?
To get a deeper stretch, contract-relax stretching employs one of the human body’s most basic responses. Remember that reflexes are unconscious, so your mind doesn’t have to work to make something happen; it just happens. Reciprocal inhibition is the physiological process that causes contract-relax stretching. When a muscle on one side of a joint contracts (shortens), the opposing side of the joint relaxes (lengthens) to allow this motion to happen. Reciprocal inhibition is the term for this.
Let’s take an example to illustrate this: Let’s imagine we’re extending our hamstrings:
You would contract the quadriceps muscle before stretching the hamstring muscle in contract-relax stretching. The quadriceps would contract in this situation, causing the muscle spindle to transmit a signal to the body. This signal reaches the spinal cord, where it is split into two signals and sent back to the body:
- One signal is returned to the muscle that sent it (the quadriceps), saying “keep shortening and tightening!” An alpha motor neuron sends this message.
- The opposing muscle (in this case, the hamstrings) receives the other signal, which reads “Relax!” “On the other hand, the other side needs to get shorter!” An inhibitory interneuron connected to the hamstring’s alpha motor neuron sends this signal. As a result, the hamstring is prevented from contracting by this inhibitory interneuron. As a result, it is completely relaxed.
When we abruptly go into a deeper hamstring stretch after the quadricep muscle has finished contracting, the hamstring muscle is more relaxed than before and can allow for more mobility!
What is the difference between this and static stretching?
Contract-relax stretching varies from static stretching in several ways, but most importantly, neurologically. The GTO, not the muscle spindle, is the signal messenger in static stretching. The GTO has the opposite response to the muscle spindle when it is stimulated by tension. The GTO suppresses the contraction of the agonist muscle, allowing the antagonist muscle to contract more. In the case above, contracting the quads would switch off the quads and cause the hamstrings to turn on and begin contracting. Instead of the reciprocal inhibition employed in contract-relax stretching, this is called autogenic inhibition. When muscle tension in the stretched muscle begins to build, the GTO response kicks in after around 7-10 seconds.
Is contract-relax stretching better or worse than static stretching?
There is a lot of research out there that shows how beneficial contract-relax stretches are in the short run. One study found that 7 days of contract-relax stretching of the neck resulted in significant gains in range of motion, but that the benefits faded quickly after the stretching was stopped. While there’s no denying that contract-relax stretching is beneficial, it’s not obvious whether it’s significantly more so than static stretching. Static stretching was compared to contract-relax stretching with varying and controlled angles in one research. With controlled angles, the results show that there was no difference between the two procedures. Contract-relax stretching, on the other hand, exhibited higher joint angles when permitted to push to the point of discomfort in range of motion. The EMG responses (or muscle activity) were not different between the two approaches even when the joint angles (or ranges of motion) were larger.
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