For the entire time I’ve been a professional coach there has always been a big question mark over the category of flexibility, both for its own sake and for performance. We have static and dynamic, passive and active, and more opinions on the matter than there are methods of stretching. Which is the best? Or are they all the best?
One type of flexibility work is called proprioceptive neuromuscular facilitation, or PNF. It’s not just a verbose term to impress your friends with. It was believed for a very long time, and still is by many, to be the best method of all for improving flexibility. A recent study in the Journal of Strength and Conditioning has tried to cast doubt on the effectiveness of this method of stretching, but did it succeed?
First things first, a little detail on PNF and what it does. This type of stretching is based on the idea that the stretch reflex is responsible for limiting the range of motion (ROM) of a joint. The stretch reflex is what we see when we are in the doctor’s office and they whack our knee with that little hammer and it makes us kick. The stretch reflex prevents injury by contracting a muscle when it’s either rapidly stretching or near its limit ROM. The reason why people with poor flexibility have this limit, according to this theory, is because the stretch reflex is protecting the muscle too soon because of muscle weakness.
As a result, PNF stretching has two aims. The first is to fatigue the muscle resisting the stretch and so improving flexibility in the short term. The second is to improve strength at the extremes of your ROM so that the body will allow greater ROM before the stretch reflex needs to protect the muscle and joint from injury.
In the study, researchers looked at the results of a bout of PNF on the neuromuscular function of the quads, vertical jump performance, knee flexion ROM, and some other things. They found that PNF stretching had no impact on any of the things they looked at and recommended against it for developing flexibility of performance.
This study is a bit disappointing to me for many reasons. I’m not sold on PNF, but the weakness of these results is apparent. First, they only looked at the short term effect of PNF, which I described above. Second, the short term effect of PNF is caused by a fatiguing of the muscle. PNF stretching is itself a workout, so it’s no surprise they didn’t see tremendous results by following one workout with another. Third, they only researched using PNF on the quads, a muscle that is not easy to use this stretching method on, especially for beginners. Assisted hamstring stretching would likely have been better, as PNF takes time to learn as well.
I’d like to seem more study on the various methods of stretching, as well as timing, and other simpler methods like daily limit ROM movement. Stretching isn’t rocket science. I mean, my dog does about three different stretches every day on her own and easily accomplishes full splits and has an impressive downward facing dog. On second thought, forget the studies, I’m just going to do what she does. She clearly knows more about the matter than the prevailing science.
1. Nicolas Place, et. al., “Effects of a Short Proprioceptive Neuromuscular Facilitation Stretching Bout on Quadriceps Neuromuscular Function, Flexibility, and Vertical Jump Performance,” Journal of Strength & Conditioning Research, 27:2 (2013)
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