Proprioceptive Neuromuscular Facilitation. Let’s just use PNF. This system of stretching is frequently used nowadays and is very effective. Here is an overview of WHY it works.
Our skeletal muscles have two types of proprioceptors (sensors). Muscle Spindles and Golgi Tendon Organs(GTO). Muscle spindles monitor the length of muscle fibers and the GTO monitors the tension. When we stretch it should only be to a point of tightness or very mild discomfort. When we stretch beyond this point we activate the ‘stretch reflex.’
Basically, this is a result of the muscle spindles sensing that the muscle length is excessive. The muscle spindles then force the muscle to contract as a protective mechanism. At this point you will either cause microscopic tearing of the muscle or related connective tissues, or you will just simply not benefit from the stretch. The GTO on the other hand causes the muscle to reflexively relax. By building up tension in a muscle without allowing it to lengthen any farther we are able to force the muscle to relax even more. This is what allows for the expanded range of motion during a stretching session.
*Warning*. If not done properly, use of this stretching system can prove harmful
*** This is a general overview of how it works. If you want more detail or have any other questions feel free to email me