Recall from our previous article [Taekwondo Flexibility 101 – Factors Affecting Stretching] about the science of flexibility I briefly touched on PNF stretching.
To recap Proprioceptors are special sensory receptors located within muscles, joints and tendons which are sensitive to pressure and tension and relay information to the central nervous system (CNS) via sensory and motor neurons.
Recall intrafusal muscle fibres or muscle spindles are proprioceptors which provide information about muscle length. Golgi tendon organs (GTO) are proprioceptors which are located within the tendon and are activated when muscle tension increases.
During a rapid stretching movement (i.e. ballistic/‘bouncing’) the sensory neuron is activated by the muscle spindles and sent to the CNS which in turn activates a motor neuron. The motor neuron then activates the extrafusal muscle fibres which in turn contract stopping a stretching action. This is known as the stretch reflex.
When a muscle actively contracts (i.e. is tensed) the GTO is stimulated in turn causing a relaxation of the contracted muscle. This is the underlying principle behind proprioceptive neuromuscular facilitation where the muscle is contracted then relaxed and passively stretched. This is known as the lengthening reaction. Relaxation can also occur in the muscle opposing the muscle experiencing the tension. This is known as reciprocal inhibition where you contract one muscle to relax another.
So OK what the hell does this all mean I hear some of you say? To simplify before stretching if you contract the muscle for around 10-30 seconds and then stretch you will see a gradual increase in the stretch ROM due to you ‘switching off’ the muscles natural mechanism to contract.
There are a number of ways this can be achieved by either self stretching or for the best results stretching passively with a partner. When doing these stretches it’s all about being in the best postural position for maximum effectiveness and be careful not to overdo it! Take a look at this video by HPCSport to get some ideas:
For safety reasons perform only one exercise per muscle group in a session and leave 48 hours between each PNF stretching routines to allow full recovery. Generally PNF stretching is not recommended for anyone under the age of 18 and should be avoided immediately before, or on the morning of competition.
If PNF stretching is to be performed as a separate exercise session, a thorough warm up consisting of 5-10 minutes of light aerobic exercise and some dynamic stretches should precede it.
Let me know what you think of this article in the comments box below. And as always, let me know your Flexibility questions.