Jules Mitchell: The Science of Stretching (LBP 009)

I got a chance to talk with Jules Mitchell right after she turned in her Master’s thesis on the science of stretching. Jules’ work blends biomechanics with the tradition of yoga to help people move better, and while looking into the research on stretching she discovered some pretty eye-opening things! For example, the idea that we can persistently stretch a muscle and have it grow longer, it turns out, is not true. We get into many other myths of stretching- and it seems there are plenty- what really works, what’s really risky, and what a better model of viewing the body might be when we put aside the “stretch tight bits to make them looser” paradigm.




Show notes

Exercise Science is a field of science with many different aspects. Jules focused on biomechanics in her Master's work, which is a science of forces and how the body responds to loads.

Yoga therapy can mean many things, but for Jules it means the application of biomechanics into yoga. It takes into consideration how the body is responding to loads, and how individuals have a loading history based on what they have done in the past, so you can't give people a blanket yoga practice.

Her Master's Thesis is basically the science of stretching.

About 1 year into the research she discovered that what she had learned from the yoga community was not supported by the science.

She went through a pretty big transformation from that and had to allow herself to unlearn and approach the science with a blank slate, and then to re-learn.

The concept of stretching in itself, at least in the yoga community, this idea that if you stretch more and stretch harder that it will get longer and you will increase your range and you will get more flexible has very little truth to it. In reality that's just damaging it [the tissue].

If you hold a rubber band and stretch it, then you release that- you release the load- it goes back to its original shape.

Lack of range of motion is not realty about lengthening. It's much more an issue of tolerance. It' s a use it or lose it thing. If you never work in that range of motion your body doesn't understand it and doesn't want to go there. So your nervous system limits your range of motion.

That argument is the hardest one to come to terms with- that for the most part range of motion is an issue of tolerance and not mechanical length.

"Tolerance" means can they go there? When they hit the end of their range, that's their nervous system limiting their range. If they were under anesthesia, they would have a full range of motion.

For those who are dealing with limited range, or flexibility issues, what can they do? Gentle, passive stretching to the point of tolerance where they can relax into it and their nervous system feels safe there, and be there for 30 seconds to no more than 1 minute.

If you really want to see changes it's really about using it. Create muscle force at that range of motion. It's active, your body has to be in control.

Jules does more strength training at these ranges of motion than passive stretching and that's where you start to see the results, because your neuromuscular system starts to work in cooperation.

Pectoralis minor (images here) if that's my issue and I want it to get longer, what would it look like to do this with strength training?

Jules says she is not going to use the word "longer" because the range won't increase. And it's not just pec minor, it's all the connective tissue around it, the ligaments of the joint, all the neighboring muscles, etc.

How that would work, you would bring the shoulder into a range where the shoulder is limited, and then you would work in that range on flexing the muscle to get it as strong as it can at that limited range. It's kind of like resistance stretching. You are stimulating the fibers so that they can communicate with your nervous system back and forth, and that's one of the most effective ways because you are developing strength and control in that joint position.

At the opposite end of that she would refer them to Restorative Yoga which is based in props. You wouldn't try to stretch as hard as you can. When you stretch as far as you can what's already compliant is going to stretch first so you're not going to hit your target tissue. But if you properly use props now there's a more equal force distribution, and you can be in that pose for a long time and communicate to your nervous system.

We are dynamic communicating organisms vs. lumps of clay that can be molded. It's all about how our nervous system regulates our muscle tissue, which transmits a force to our connective tissue.

We have to look at the tensegrity model where muscle fibers literally embed into connective tissue. If you think about it your muscles are contractile tissues- that's what they do. They produce force. the sarcomeres are literally transmitting force to the connective tissues all around, not just length-wise but also radially outwards in all directions and dimensions.

If you don't have the ability to control the muscle force in all dimensions you run into weakened muscle force. We want our muscle tissue to be strong enough to move.

[said another way] We want to be stiff- just stiff in all ranges of motion, not just one range of motion. In a full range of motion "stiff" makes us powerful beings and now we have a full range.

This idea that the more flexible we are the better off we are- when reality those people have more trouble "holding themselves together".

How does someone get "tight" in the first place?

Jules does not use that word, because there is no definition for tight. It's not a mechanical term.

If we're going to go with air quotes "tight", or talk about limited range of motion- that you can only take your joint in certain positions- that happens, 9 times out of 10, because it hasn't been used there, so the nervous system doesn't put it there. The muscle fibers aren't strong enough to maintain that force regulation through the body. It will go to where it's safer. It's not a matter of tightness, it's more a matter of communication.

Jules mentions Van der Wal's article (which is linked below in the resources). He was groundbreaking in this research. He was an anatomist and he realized that our mathematical models for human movement weren't fitting in to how we viewed anatomy. We really aren't a collection of muscles. There's never any part of the body that's slack. His work was groundbreaking for understanding tensegrity. Force transmits radially through out the body, so everything is always under some degree of tension.

One of my favorite Dr. Rolf quotes of all time: "Wherever you think it is, it ain't"

Stretching an injury: we have a cultural misunderstanding of stretching. We have an idea that if it hurts, stretch it. People who are in pain should just leave it alone instead of stretching it and instead move it and use it so the muscle fibers will direct the loads where it's supposed to go.

If you have a tendon or ligament tear, that you want to wait before you stretch. A big problem is that the inflammation goes down within a few days and they no longer feel the injury and so are ready to go right back to stretching it. It's a good 6 weeks before the collagen can take stretching. And that's conservative; A safe measure would be 1 to 2 years.

Most often it takes some re-injury before people are willing to hear that advice about not stretching.

Nobody cares about stretching the way the yoga community does. In the research and in the Exercise Science community there is no interest in these extreme ranges. In fact, in the research Jules was looking at- in many cases people who practiced yoga did were excluded from the studies because they don't expect these extreme ranges.

The biggest surprise was that there was very little research on yoga and flexibility. She found one short study. The yoga community has done some great research but more on mental health and relationships.

However in 2012 Yoga Journal did a study on the 18 million Americans that practice yoga and the number 1 reason they were practicing yoga was to increase flexibility, so there' s a big disconnect [between the research and the reasons people seek out a yoga practice].

When flexibility is the issue for a person, stretching is not going to help. Moving frequently in more full ranges of motion and incrementally increasing the load is actually the answer.

Jules believes that is what yoga was meant to do- yoga is using your body weight in a bunch of different positions.

But we have gone in this "push harder, harder, harder" mentality and you have 80 people in a classroom, and some have been doing handstands for 10 years, and some just got off their couch, and you're giving them the same class. That's scary.

You can't expect a yoga teacher, or any other fitness instructor, in a group setting to be able to fully take into consideration how you have used your body for its whole history. And you have to keep that in mind.

In her own practice Jules is currently playing with decreasing her flexibility. She was never hypermobile, but she's learned that she was really flexible and she was really weak in these full ranges of motion. Increasing the muscle contraction at the end range has got her feeling better than she ever has.

Home play!

I am in the process of finishing the first Liberated Body Guide (short guides of what works for what) and the first one will be the Short Hamstrings Guide ("short" in air quotes, but Limited Range of Motion in Your Hamstrings makes for a wordy title...). Because my world is fairly hamstrings-centric right now due to the guide, let's play with load instead of stretching to see how the hamstrings respond. For one week play with swapping out any stretching protocol you might have for squatting, lunging, or a Founder (from the previous episode with Eric Goodman) and see what response you get. I'm talking about body-weight movements that are not high velocity or high quantity. This is good for both the "tight" types and the Gumby types, so everybody wins!


Jules Mitchell's site

Jules' most current blog post which covers in more detail what we talked about in the interview: Stretching and Muscle Control

Restorative Yoga

Jaap van der Wal article  (It's exceptional, print it out and digest slowly...)

Jules' post that I refer to in the home play section: Are You Really Stretching What You Think You Are?