Proprioceptive Neuromuscular Facilitation (PNF) stretching was first developed to help rehabilitate patients by relaxing muscles with increased tone or activity. These principles can be applied to any individual, however, and although it is generally recommended to perform these techniques with a partner, using tools such as stretching bands or belts can help stretch certain body parts while still maintaining PNF stretch techniques.
PNF stretching may be superior to other stretch techniques because it facilitates muscular inhibition by using both passive and active movements (concentric and isometric) and muscle actions. The biggest downfall of these stretch techniques however, is that many body parts require a partner to help achieve PNF stretching, and they must be done with correct form and technique in order to work properly.
There are 3 main types of PNF stretches that I have detailed below. In each technique, the first phase incorporates a passive pre-stretch that lasts 10 seconds. The initial pre-stretch is then followed by a 2nd and 3rd phase which varies by technique.
Following the initial 10-second pre-stretch, a force is applied to the muscle in question while the individual being stretching "holds" the stretch isometrically. The "push" that is causing the isometric hold should be resisted against by engaging the muscle in question. The hold is held isometrically for 6 seconds and then relaxes. The last passive stretch is then held for 30 seconds and should be of greater magnitude due to the "autogenic inhibition" caused by the isometric active stretch.
Following the initial 10-second pre-stretch, and similar to the "hold-relax" technique, a force is applied in an attempt to stretch the muscle in question. In the hold-relax technique, the individual is instructed to not let the body part move and simply hold the muscle isometrically while resisting the force. In the contract-relax technique, however, the individual should actually complete range of motion, concentric contraction and then relax. A passive stretch of greater magnitude can then be performed for 30 seconds.
Hold-Relax with Agonist Contraction
This technique is performed exactly the same as the hold-relax technique in the first 2 phases, except in the 3rd phase, not only is the muscle in question being passively stretched, but there is an agonist contraction. For example, if the hamstrings were being stretched, then during phase 3, the quadriceps would contract to further accentuate the passive stretch.