There are many thoughts on the various types of stretching used in an Athletic Training environment. Often people are attached to one method or another based on what their personal experience has been. With all of the various methods I began to wonder what makes Proprioceptive Neuromuscular Facilitation (PNF) so special; why is it that in every clinic where I have spent time, PNF is the preferred method. Furthermore if it is used so frequently is it a matter of personal preference or is there research to back up its effectiveness. Because of these questions I chose to find the answers to the question, “Does the use of PNF on lower extremity injuries increase tissue extensibility?”
It is critical for a healthy athlete to have a balanced program of exercise including strength, stability and flexibility. If any of these areas are lacking it is possible to develop various injuries or deficiencies in the body. One of the many roles of an Athletic Trainer is to work with the athlete to maintain this program before, during and after an injury occurs. An important part of any program is stretching, and stretching correctly so the maximum benefits are provided to the athlete’s body. We need to know what type of stretching will best benefit the particular situation that we are faced with as well as why we are making that choice. PNF is a style of stretching, with multiple variations, that is frequently used in maintenance and rehabilitation settings. We will look into various research studies in order to determine if this method of stretching really works or if it is just a personal preference of some Athletic Trainers.
I looked at three studies related to PNF stretching, each with slightly different objectives such as its contralateral effects, different intensities of PNF and the differences if can make after a single session. As a whole there was a significant improvement in tissue extensibility and increased range of motion in all of the studies. The one thing that these studies were not able to determine is the length of time the results will last; that question was not the focus of these studies.
In their study O’Hora, Cartwright, Wade, Hough and Shum (2011) looked at how the use of PNF would affect the length of a hamstring with a single session of PNF. They used three groups of 34 healthy subjects for their study; one would be the control group, one would use static stretching and the third would use PNF. Passive knee extension would be measured goniometrically before and after the use of static stretching and PNF. In the course of their study they determined that “…PNF produced a significantly greater average in passive knee extension of 4.27°” as well as a substantial rise in the flexibility of the hamstring (O’Hora, 2011, Results). If PNF can cause such a change with a single session, then surely repeated sessions would be beneficial to our athletes.
Another study I found interesting was based on the use of PNF but using a different intensity in the actions. Five groups were tested using one as a control group, and one group each using 20%, 40%, 60% and 80% of maximum voluntary isometric muscle contraction. The Contract-Relax (CR) method was used in which a muscle is isometricly contracted then allowed to relax for a few seconds before starting the maximum contraction again. The participants hamstring flexibility was tested twice a day using a goniometer before and after stretching. Khodayari and Dehghani (2012) were able to reach the conclusion that this method did cause significant changes in the flexibility of the hamstring. Additionally they found that “CR stretching using submaximal contractions is just as beneficial as improving hamstring flexibility as maximal contractions” (Khodayari and Dehghani, 2012, Discussion & Conclusion). This is of particular importance because it shows that an in the case of an injury when maximal contraction is...