Stretching Doesn't Work (the Way You Think It Does)
Sep 22, 2014
Stretch Your Bits or Stretch Your Mind?
I’ve had a few things come up recently that have me rethinking the common stretching belief that goes something like this: stretch tight bits in your body and they will get longer/more flexible/more supple.
The things that have me rethinking this are:
- An interview I did on the Liberated Body Podcast with Jules Mitchell who is writing a book (and just finished a thesis) on the science of stretching.
- A guide I am putting together on how to resolve short hamstrings (it’s out on Liberated Body in October), which had me immersed in the research about how hamstrings specifically manage to return to a more functional length.
- And last but not least, I am reading Katy Bowman’s new book Move Your DNA where her insights on sarcomeres have my attention (plenty of other things too, but I’m already trying to keep this post from becoming epically long).
I’ll do my best to summarize the a-ha moments that have sprung out of these three things.
Your Nervous System Runs the Show
In her interview with me, Jules Mitchell* talked about how she began her thesis with the intention of taking a biomechanical view into yoga asana, which is exactly what she does. However, because she started her work from the perspective of a yoga teacher- with all the training that had told her that stretching leads to increased flexibility, she was surprised to discover that the research on stretching did not bear this idea out.
She discovered this idea - that if we stretch more and stretch harder that our tissue will change - was untrue. In reality, we are not lumps of clay that can be molded by persistently tugging on things. This is because our nervous systems are running the show.
So what does that mean? That means that unless you are under anesthesia (where you will miraculously gain full and even excessive range of motion, but I do not recommend attempting to go through life under full anesthesia simply for its flexibility gains), your ability to stretch at any range is determined by your nervous system’s tolerance to that range.
As in, when you have super short hamstrings and you try to forward fold and meet rigid resistance, it is not that you need to pull on your hamstrings like they are inanimate taffy, because you can’t. Your nervous system is the thing giving you that firm end range, and it’s basically saying, “Nope. Sorry buddy. I don’t feel safe there, so I’m not going to let you go there.”
Getting pushy about it and trying to force your hamstrings into ever deeper end ranges will have one of three outcomes:
- Nothing will change
- Your hamstrings will get shorter
- You will injure your tissue (which, P.S., has about a two-year healing period if we’re talking about a tendon injury).
I recommend not trying to force override your nervous system on issues of flexibility. It will win. It will be unpleasant.
Your Body's Emergency Brake
Why would the nervous system not feel safe and therefore limit your mobility? Because that range is unfamiliar, or because compensatory patterns in your body have determined that certain parts of you need to function as an emergency brake in order to hold it all together (and of course these two things are not mutually exclusive). Both boil down to issues of motor control (plenty more to chew on here) and of Davis’ Law, which can be (over) simplified to, “use it or lose it.”
While working on the Liberated Body Short Hamstrings Guide, I kept coming back to the issue of how the hamstrings function, in some chronically short-hamstringed people, as an emergency brake. This kind of compensatory pattern happens for plenty of reasons, but top among them might be under active deep core musculature, too rigid core musculature (yes, underactive and too rigid can come together), weakened adductors, and more. If these or other key stability structures can’t fully do their job, the hamstrings are at the ready. They sub in for a lack of support elsewhere by battening down the hatches.
To go back to the emergency brake analogy - if your car were parked on the edge of a cliff and was held there only by its emergency brake, would you release it? Not if you are sane. This is the same decision your nervous system is making when you attempt a forward fold and are stopped prematurely.
Those Naughty Sarcomeres
In regards to the use-it-or-lose-it part of the flexibility equation, let’s talk Katy Bowman**, moving your DNA, and the sarcomeres. Bowman has been a champion of getting people to understand the difference between frequency and intensity. In short, that what we are doing with our bodies most of the time thoroughly trumps how hard we may be capable of working out (or stretching) for a small portion of our day. In relationship to flexibility, this means that if we, for example, sit in a chair with our hamstrings contracted from both ends all day long, we will gradually develop short hamstrings.
Here is an extremely pared down, Cliff’s Notes version of Bowman’s writing in Move Your DNA and also here on her blog on the role the sarcomeres play: Sarcomeres are the basic contractile units of our muscles. Muscles move because sarcomeres generate force and move. When you are often in the same position - as with our contracted-hamstrings-in-the-chair example - your sarcomeres change on the cellular level in a way that makes it easier for you to do more of what you are already doing. Yes, those naughty sarcomeres will actually cannibalize themselves and grow themselves to set your chair-shape as your new normal.
That said, the way to approach rehabilitating this would be to move with more normal hamstrings length more frequently. For example: to use a standing desk for all or part of the day, to sit on the floor with our legs outstretched in front of us (if we can accomplish that without rounding our backs, another symptom of short hamstrings), wearing neutral-heeled shoes, and to walk and to take frequent movement breaks, among other things.
The road to rehabilitation would not look like stretching the bejeezus out of your hamstrings at their absolute maximum end range for somewhere in the neighborhood of thirty and ninety seconds per day.
Bringing Mitchell’s and Bowman’s work together, this kind of rehabilitation accomplishes a few key things. First, it reminds your little sarcomeres what length you would like things to be by gradual, incremental loading of your body in healthier ranges of movement. Second, taking more opportunities for natural movement more frequently (oversimplified definition alert: natural movement = accomplishing the movements that our ancestors used to need to do to survive - like walking, or bending, or climbing - with proper alignment) develops strength and adaptability. This allows your nervous system to feel safe about testing out new ranges of motion, while simultaneously unraveling the compensatory patterns that make your nervous system put on the brakes in the first place.
A Tale of Two Feet
What might this look like in practice? Let me tell you about my feet. Last summer I still had to slap on my rigid hiking shoes in order to get out on the rocky trails here in New England. Whenever I attempted to wear a more flexible-soled shoe, I was one sore-footed girl. Determined that my feet could be more supple, I spent the year wearing only neutral-heeled, flexible-soled shoes, taking plenty of barefoot time, increasing my walking mileage, and intentionally seeking out as much diverse terrain as I could find.
Fast forward to the end of this summer and I have been hiking daily - up steep inclines, on slick shale, on rocky ground and tangled stumps - only in my Unshoes. And what’s amazing is that these hikes also manage to feel like a delicious foot massage no matter how long I’m out on the trail. I find myself intentionally stepping on the rockier areas of the trail because it feels good on my feet. What happened there?
I incrementally - over one year - loaded my feet differently, and as a result the 33 joints that live in my tootsies are now much more supple and flexible. My feet are also stronger. Flexible and strong like to show up to the party together. Go figure.
Stretching Movement Rules to Live By
So is stretching the devil? Nah. Frequent, intermittent stretching that is within your range and not red-lining it for your abilities helps you to explore your movement ranges and therefore helps you to (very gradually) remodel yourself at the cellular level to a more mobile version of yourself.
This is a complex issue for which much more could be said, but I have already written a short novel, so in closing here are a few bullet points that we might want to consider so that we can re-frame how to become more flexible. Perhaps we should:
- Stop with the no-pain-no-gain crap and instead accept that The Goldilocks Principle holds true for human tissue: not too much, not too little, but just right amounts of input keep us healthy and mobile.
- Stop with the “stretch tight bits to make them looser” and “we are inanimate lumps of clay” models. We are alive. Our nervous systems are in charge. We need to have a long-term dialogue with it, not pretend we can boss the CNS around.
- Stop pretending we can put movement into a bento box of “exercising” and “non-exercising” time when what we are doing all the time - movement not exercising -is what is determining our shape and mobility.
- Stop stretching at extreme maximum capacity at rare intervals and instead take kinder intermittent stretch breaks.
- And while we’re at it, let’s altogether drop the idea that being bendy is somehow better. Functional length is better; hypermobile is trouble.