Improve Flexibility with Research-Supported Stretching Protocols | Huberman Lab Essentials

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Welcome to Huberman Lab Essentials, >> [music] >> where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I’m Andrew Huberman and I’m a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today we are going to discuss the science and practice of flexibility and stretching. The important thing that I’d like you to know is that flexibility and the process of stretching and getting more flexible involves three major components. Neural, meaning of the nervous system, muscular, muscles, and connective tissue.

Connective tissue is the stuff that surrounds the neural stuff and the muscular stuff, although it’s all kind of weave together and braided together in complicated ways. So, here’s a key thing that everyone should know, whether or not you’re talking about flexibility or not. Your nervous system controls your muscles. It’s what gets your muscles to contract. So, within your spinal cord you have a category of neurons, nerve cells, that are called motor neurons.

Those neurons release a chemical. That chemical is called acetylcholine. The release of acetylcholine from these nerve cells, these neurons, onto the muscles causes the muscles to contract. And when muscles contract, they are able to move limbs by way of changing the length of the muscle, adjusting the function of connective tissue like tendons and ligaments. Now, within the muscles themselves, there are nerve connections.

And these are nerve connections that arise from a different set of neurons in the spinal cord that we call sensory neurons. These spindle connections within the muscle that wrap around the muscle fibers sense the stretch of those muscle fibers. So, now we have two parts to the system that I’ve described. You’ve got motor neurons that can cause muscles to contract and shorten, and we have these spindles within the muscles themselves that wrap around the muscle fibers, and that information is sent from the muscle back to the spinal cord. It’s a form of sensing what’s going on in the muscle.

Now, why would that be useful? Well, what this does is it creates a situation where if a muscle is or is stretching too much because the range of motion of a limb is increased too much, then the muscle will contract to bring that limb range of motion into a a safe range again. Okay, so just to clarify, this whole thing looks like a loop, and the essential components of the loop are motor neurons contract muscles, sensory neurons that we call spindles are sensing stretch within the muscles, and if a given muscle is elongating because of the increased range of motion of a limb, those sensory neurons send an electrical signal into the spinal cord such that there is an activation of the motor neuron, which by now should make perfect sense as to why that’s useful. It then shortens up the muscle. It actually doesn’t really shorten the muscle, but contracts the muscle.

It brings the limb back into a safe range of motion. So, that’s one basic mechanism that we want to hold in mind. This idea of a spindle that senses stretch and can activate contraction of the muscles and shorten the muscles. The next mechanism I want to describe, and once again, there are only two that you need to hold in mind for this episode, has to do with sensing loads. So, at the end of each muscles, you have tendons typically, and there are neurons that are closely associated with those tendons that are called Golgi tendon organs, right?

These are neurons that are sensory neurons that sense how much load is on a given muscle, right? So, if you’re lifting up something very, very heavy, these neurons are going to fire, meaning they’re going to send electrical activity into the spinal cord, and then those neurons have the ability to shut down, not activate, but shut down motor neurons and to prevent the contraction of a given muscle. So, for instance, if you were to walk over and try and pick up a weight that is much too heavy for you, meaning you could not do it without injuring yourself. There are a number of reasons why you might not be able to lift it, but let’s say you start to get it a little bit off the ground or you start to get some force generated that would allow it to move. But, the force that you’re generating could potentially rip your muscles or your tendons off of the bone, right?

That it could disrupt the joints, that could tear ligaments. Well, you have a safety mechanism in place. It’s these Golgi tendon organs, these GTOs as they’re called, that get activated and shut down the motor neurons and make it impossible for those muscles to contract. There are also mechanisms that arrive to the neuromuscular system from higher up in the nervous system, from the brain. And those mechanisms involve a couple of different facets that are really interesting and I think that we should all know about.

In fact, today I’m going to teach you about a set of neurons that I’m guessing 99. 9% of you have never heard of, including all you neuroscientists out there, if you’re out there. And I know you’re out there. That seem uniquely enriched in humans and probably perform essential roles in our ability to regulate our physiology and our emotional state. So, within the brain we have the ability to sense things in the external world, something we called exteroception, and we have the ability to sense things in our internal world, within our body, called interoception.

Interoception can be the volume of food in your gut, whether or not you’re experiencing any organ pain or discomfort, whether or not you feel good in your gut and in your organs. The main brain area that’s associated with interpreting what’s going on in our body is called the insula, i n s u l a. It’s a very interesting brain region. It’s got two major parts. The front of it is mainly concerned with things like smell and to some extent vision.

Like if you smell something good to approach it or if you smell something bad to avoid it. The posterior insula, the back of the insula that is, has a very interesting and distinct set of functions. The posterior insula is mainly concerned with what’s going on with your somatic experience. How do you feel internally? It mainly batches information into yum, I want to keep doing this or approach this thing, or continue down some path of movement or eating or staying in a temperature environment, etc.

Or yuck, I need to get out of here. I don’t want any more of this. I don’t want to keep doing this. This is painful or aversive or stressful. In your posterior insula, you have a very interesting population of very large neurons.

These are exceptionally large neurons called von Economo neurons. Neurons that are again, unbeknownst to most neuroscientists, and they seem uniquely enriched in humans. Why is that interesting? Well, these von Economo neurons have the unique property of integrating our knowledge about our body movements, our sense of pain and discomfort, and can drive motivational processes that allow us to lean into discomfort and indeed to overcome any discomfort if we decide that the discomfort that we are experiencing is good for us or directed toward a specific specific goal. And then, there’s the other really interesting aspect of these von Economo neurons, which is that these von Economo neurons are connected to a number of different brain areas that can shift our internal state from one of so-called sympathetic activation.

So, this is a pattern of alertness and even stress, sometimes even panic, but typically alertness stress, to one of so-called parasympathetic activation. To one of relaxation. Oftentimes you’ll hear that stretching should be done by relaxing into the stretch. Well, what does it actually mean to relax into the stretch? Well