PNF - Proprioceptive Neuromuscular Facilitation

PNF, also referred to as contract-relax stretching, is a very effective form of increasing flexibility. An athlete uses PNF when deliberately engaging the muscles they are stretching against a relatively immovable resistance for short periods, interspersed with short periods of relaxing further into the stretch. Through this mechanism, athletes are able to move well beyond the range of motion (ROM) that they would be able to reach with typical static stretching, or even assisted static stretching. Reaching and holding this position of increased ROM helps to truly increase the effective and achievable ROM for that athlete.

Implementing PNF into your stretching protocol is pretty simple. PNF is generally more effective with a partner, but can be performed solo giving thought into how to anchor positions. For the sake of discussion, we will utilize the typical pike stretch as our case study. The athlete should sit in a pike position with legs straight and together. The partner should set up behind him, placing hands on the lower back. Be sure that pressure is applied low enough that no strain is placed on the lower back. Once the partner is in place the athlete should engage his hamstrings (the target muscles) by sitting up against the partner. The partner should not allow the athlete to move much. The engagement does not need to be at maximal effort as a moderate engagement will suffice. More aggressive engagements will just make holding the position more difficult. After 5-10 seconds of engagement the athlete should relax down into the stretch. At this point the athlete should be further than he was prior to the engagement. Repeat the engage-relax cycle a few more times, then hold the final position for 15-30 seconds.

An additional piece of PNF is to engage the agonist muscle to induce a reciprocal inhibition. Regarding the aforementioned pike stretch, the athlete should be instructed to contract his hip flexors, abs and quads. This can be done in a couple of ways. 1) Do some active ROM training just prior to stretching into the pike. Seated, piked leg lifts, hanging leg lifts (strict) and the like would be good examples of these types of exercises. 2) Actively contract quads, hip flexors and abs when in the 15-30 second hold phase at the bottom of the stretch. Be aware that this may induce cramping in the agonist muscles.

When a joint is moved toward the limit of its flexibility in a given direction, your neurology will engage the antagonistic muscles to slow down movement to help prevent you from taking that joint beyond a stable point. This set-point varies from person to person, at times dramatically. There are many factors that will affect this set-point, the first being genetic. There is a very strong genetic tie to mobility. The other major factor is environmental. If an individual never moves through wide ROM then the set-point will gradually back further and further away from that wide ROM. We must keep moving ourselves through full ROM to maintain or improve that capacity.

The primary purpose of PNF is to "trick" a muscle into relaxing past its neutrally perceived set-point. Through autogenic and reciprocal inhibition the muscle relaxes and will lengthen beyond where it would stop under a steady static stretch. Through this process a body's set-points are changed and functional ROM is increased.

Important safety notes: PNF stretching should never be done cold. It should also not be done prior to a workout, or competition as it will significantly reduce your contractile potential for a few hours after the PNF session. PNF stretching should not be done with children as joint tissue and bone structures are not fully developed and this can lead to damage of those structures. Kids simply need to work on movements that develop ROM and utilize static stretching on a regular basis.