Updated: May 1
A full video reading through this article is available at this link
Alex Hutchinson recently wrote an article on OutsideOnline.com touting numerous claims pertaining to stretching (here). He wrote, “So anointing flexibility as one of the five “major components” of physical fitness gives it undeserved importance, and leads people (including, apparently, personal trainers) to spend time that could otherwise be devoted to other activities with far better return on investment.” He comes to this conclusion after dastardly misunderstanding the research that he cites. I’ll explain below, followed by a science experiment that you can conduct to prove the mostly untaught benefits of static stretching. I’ll also compare it to other forms such as dynamic and PNF (proprioceptive neuromuscular facilitation) stretching.
He notes, “According to the research Nuzzo summarizes, greater flexibility as measured by the sit-and-reach test isn’t associated with longer life.” Any time that someone uses the word “associated” when pertaining to a study, means that they are pulling from a cohort study. An observational cohort study, for example, looks at large groups of people while comparing them for possible correlations. It is NOT POSSIBLE to definitively prove anything EVER in a cohort study. That’s not even the purpose of these studies. Their goal is to find possible connections that can later be studied in a more controlled manner. Just because a possible correlation exists, doesn’t mean that the two are actually correlated. Check out this funny website showing how statisticians can find a correlation with things that quite obviously cannot be connected in any way.
Think about this logically for a minute… how would it be possible to test whether one single stretch prolonged the life of a group of people? They would have had to control every element of their lives while making sure that some people performed that one stretch, while forcing the other people not to. That’s absurd. Basically I’m saying never listen to the results of a cohort study as “proof” or “evidence” for anything, since they simply are not.
The association of “living longer” isn’t a good measure of whether stretches actually help people. Alex also mentions how these cohort studies don’t show evidence that people avoid falls due to the sit-and-reach stretch… though that in no way means that a properly designed stretching routine (stretching muscles that are overactive) will not help. If a person’s inner thighs (adductor muscles) are tight (overactive), then this will pull the femur more inward (creating a valgus knee). This position will allow more of the force to be directed onto the ACL (anterior cruciate ligament) while climbing stairs, for example. Stretching these adductor muscles will aid in creating a proper position, relieving the stress on the ACL. In some cases this is not enough -- someone should work out the outer butt muscle (gluteus medius) in addition to stretching the adductors.
The above explanation directly contradicts Alex’s claims that “flexible doesn’t seem to protect you from injury either.” There are many instances in which statically stretching a muscle will prevent injuries, especially while working out the opposing muscle (antagonist). I have personally helped numerous people who previously suffered from plantar fasciitis, lower back pain (though common recommendations of stretching for this are incorrect), thoracic outlet syndrome, knee pain, and even migraines by addressing the overactive muscles with stretching, while activating the underactive muscles with strength training. Doing either without the other is not nearly as effective.
Alex goes on to write, “being flexible doesn’t improve your sports performance.” This worded as stated is correct, though having overactive muscles will hinder your athletic performance. He goes on to correctly note that stretching right before running (as our entire field used to teach) will indeed “decrease strength” for a temporary period of time as this 2010 study notes. This was specifically looked into after many studies noted a higher injury rate for those who stretched before running, such as with this study. This is not due to the neuromuscular signaling which Alex notes as the reason for this decrease in strength, however.
When a muscle is stretched, some (not all) of the proteins (actin and myosin filaments) that create the contractions will separate too much to create a contraction, as illustrated in the length-tension relationship, noted in this 1994 study. Think of it this way… if the muscles are in their optimal position before stretching, then the act of stretching will bring them too far apart to be able to create contractions with all of the muscle fibers. If the stretching instead actually puts the muscles in the optimal position, this will make contracting more efficient. I first wrote about this in my provisional patent application in 2008, later publishing it in 2009. Pinto in 2012 came to the same conclusion as me when saying “The tension produced by the entire muscle fiber can thus be related to the length of an individual sarcomere, which is related to the joint angle. Within the optimal range of sarcomere lengths, the maximum number of crossbridges can form and the tension produced is greatest,” in this 2012 study.
This actually confirms the rational I mentioned that stretching overactive muscles will help correct your position back to neutral. Since stretching decreases contractions, and doing so on muscles that want to help too much, will decrease the amount that they will help.
Let’s take the specific example of plantar fasciitis in explaining this further… plantar fasciitis is heel pain caused by a movement of the heel bone (calcaneus) up in elevation from its neutral position, due to overactive calves (gastrocnemius, soleus, plantaris), along with underactive shin muscles (tibialis anterior). The tight calves pull up the bone, causing the plantar fascia to stretch, causing pain usually on the heel. Stretching the calves will allow the bone to shift back down, while activating the shin muscles will keep the bone down from the other end according to the principle of Davis’ Law (first mentioned in 1912). Correcting this muscle imbalance will allow for the calves to function properly without leading to injuries, while ignoring it will cause more pain and malpositioning.
It’s important to note that the only stretching I have been discussing thus far was static, while Alex’s article mentions dynamic stretching as a good alternative. There is also a form of stretching that is superior known as PNF as shown in this 2016 study. PNF usually involves a professional passively stretching someone while having them contract the opposing muscle for a specific amount of time (I do 8 seconds). The previously mentioned study explains a self-administered method while having them contract for 10 seconds.
Dynamic stretching has been shown to not cause the same level of ill effects that static stretching causes in runners, though does not have any real evidence for its efficacy. Just because butt-kickers and high-knees do not cause as much of a stretch, doesn’t mean that they are useful.
The most important element to proper joint movement is the release of synovial fluid. This can be accomplished by taking glucosamine (which basically turns into glycosaminoglycans -- the precursor to synovial fluid), or by doing a cardiovascular warm-up. This means that performing specific dynamic movements is likely not a factor, but rather that someone should do a cardio style warm up. Though I would argue that dynamic stretches are not as good of an idea due to them still stretching the muscles past what the muscles would ever do in any sport.
Since stretching optimally-lengthed muscles causes a decrease in strength, then even a small amount of stretching is not a good idea pre-workout. Statically stretching usually takes 20-30 seconds, while each dynamic stretch takes less than a second, usually only for 10-20 reps (maybe 3-4 seconds total of stretching). This could explain the improvement of dynamic stretching over static, though still not being a good idea.
As promised, let me explain an easy science experiment that you can do to prove the efficacy of stretching;
1) Find a muscle that you use far too much during an exercise, such as the shrugging muscles (trapezius & levator scapulae) for many people during a pulldown. These muscles (or overactive biceps) will help out too much, instead of allowing the lats (latissimus dorsi) to do most of the work.
2) Perform the exercise (lat pulldowns for the example above).
3) Stretch these overactive muscles for 30 seconds to 1 minute.
4) Perform the exercise again and notice how these overactive muscles will not help as much as they did during your first set.
This simple experiment will show those who can feel their muscles that stretching is very effective in the short term in rebalancing our muscles. Other than short term gains in flexibility, stretching a muscle for at least 5 days and for a total of 5 minutes each week will show a gain in flexibility in the long run, according to this 2018 study.
In conclusion, stretching is in fact necessary for all people who house muscle imbalances, which in my professional experience is every person I’ve met. Do not ever trust any cohort study as evidence for anything. Static stretching is good, while PNF stretching works even better… though dynamic stretching should likely not be used as a warm-up.