What is PNF, Muscle Spindles, and Golgi Tendon Organ?
From personal experience, both while working with patients and treatments being applied to myself, PNF speaks volume in terms of increasing ROM and depending on a few elements (correct timing and conditions of injury) it can increase performance. So how does this stuff work right? Let us start with Muscle Spindles (MS) which are located near the belly of the muscle. The feedback system is triggered once MS feels the muscle being stretched, such as PNF. Simply put, the trigger uses sensory neurons to relay news to the spinal cord. Then, sensory neurons synapse, aka texts messages, the alpha motor neurons asking them to contract and resist being stretched. At this time, on the opposite end, GTO kicks-in its responsibilities. It is easy to understand the location and action of Golgi Tendon Organ (GTO) by simply looking at the name, the tendon. The feedback is triggered once GTO detects any kind of tension, such as PNF, being applied to the tendon. Simply put, the trigger uses sensory neurons and synapses (aka texts messages) to communicate with inhibitory interneurons, which in return forwards the messages to alpha motor neurons. Finally, the inhibition of alpha motor neurons helps muscles (the muscle we are trying to lengthen) relax thus relieving the tension applied tot he tendons. However, it is important to understand that PNF is to help increase ROM and performance only when completed under the correct condition (1) and sometimes can be contraindicated when the muscles, tendons, bones, and joints are injured (Susan Adler, & Dominiek Beckers 2008, pg14)
Reference: 1) Kayla B. Hindl1, Tyler J. Whitcomb, Wyatt O. Briggs, Junggi Hong (2012): Proprioceptive Neuromuscular Facilitation (PNF): Its Mechanisms and Effects on Range of Motion and Muscular Function. Journal of Human Kinetics volume 31/2012, 105-113 DOI: 10.2478/v10078-012-0011-y 2) Westwater-Wood S, Adams N, Kerry R (2010): The use of proprioceptive neuromuscular facilitation in physiotherapy practice Physical Therapy Reviews Vol.15 No.1, p23-27 3) Susan Adler, &
4) Pictures were taken from wikihow.com Dominiek Beckers (2008): PNF in Practice an illistration guid. Rehab Center Hoensworth .1, p14.