Most people think of their muscles as being either “long” or “short”, and that during a stretch, they are targeting their “short” muscles by physically “lengthening” or “loosening” them. In this stretching paradigm, our muscles are mold-able tissues like taffy or play-doh which we can form into a shape of our choosing by simply pulling or pushing on them. For example, when we fold forward into paschimottanasana (seated forward fold), we tend to imagine that our hamstrings are physically growing longer in that moment of our stretch in the same way that taffy would grow longer if we tugged on both of its ends for awhile. We imagine that when we release paschimottanasana, our hamstrings remain just a bit longer than they were before we did the stretch. And we also imagine that the longer and deeper we hold a pose like paschimottanasana, the longer and looser our hamstrings become.
This stretching paradigm is what most of us were taught in our yoga classes, workshops, and teacher trainings. It’s completely understandable that we might see the body as working like this, but new research is revealing a very different version of the biomechanics of stretching.
We all know that when we stretch, we experience a feeling of “tightness” at our end range of motion - a sensation that limits us from moving any deeper into the stretch. We have traditionally defined this “tight” sensation as the result of having reached the end length of the muscle(s) we’re stretching. In other words, we pulled on the ends of our muscle until we reached its maximum physical length, and once we hit that boundary, the stretch stopped and we felt the “tightness”. With enough stretching, we could increase the length of our muscle and therefore move further into our stretch with time.
For example, if you happen to work on your computer for 8 solid hours a day (and if you don’t take frequent intermittent stretch breaks for your shoulders - hint hint :) ), the brain becomes very familiar with the arms-forward position that you use while typing and considers that range safe. Then later, if you decide to do a chest stretch in which you take your arm out to the side and then behind you, the brain doesn’t feel that that movement is safe because you so rarely go there, so it will limit your range very early on in the stretch.
A major takeaway from this new flexibility paradigm is that when we increase our range of motion through stretching, it isn’t because we pulled on our tissues and made them longer. It’s because we visited the edge of our stretch (also called stretch “tolerance”) enough times that our brain started to feel comfortable there and it began to allow us to move deeper into that range.
It’s definitely interesting and more scientifically accurate to understand this previously-overlooked role that our nervous system plays in flexibility. But whether it’s your nervous system or the physical length of your muscles limiting you in a stretch, why does it matter? Isn’t a stretch a stretch, regardless of the mechanism behind it?
That’s a great question - I’m so glad you asked! The main answer has to do with what tissues are being targeted when we stretch. We often think and talk about stretching our muscles in our yoga poses (i.e. paschimottanasana stretches our “hamstrings”), but in truth our muscles are surrounded by, interwoven with, and inseparable from our fascia. Our fascia is our incredible body-wide web of connective tissue that is literally everywhere inside of us, and it includes our tendons and ligaments. Muscles and fascia are two distinct tissues with different properties, but both are affected when we stretch. And how we choose to stretch, which is based on whether we believe that we’re physically lengthening our muscles (old paradigm) or increasing our nervous system’s tolerance for the stretch (new paradigm), determines how our fascia will be affected during the movement. (Preview for Part 2 of this post: if we’re going with the older “pulling on our tissues like play-doh" paradigm, we’ll feel more drawn to stretching deeper and harder in our poses, which is much more likely to simply damage our tissues than give us the flexibility we seek.)
I’ll elaborate more on this and other important topics, like how we might choose to apply this new information to our yoga practice and teaching, in my next blog post. Stay tuned, guys! And in the meantime, if you’re interested in further reading, check out this awesome article by Jules Mitchell (written for a pretty science-oriented reader). See you for Part 2 soon!
For more awesome science-based yoga information from Drishti owner Jenni Rawlings, check out her website at www.jennirawlings.com.