Huberman Lab
Essentials: Improve Flexibility with Research-Supported Stretching Protocols
18 Jun 2026
Transcript generated automatically by AI and may contain errors.
Chapter 1: What are the biological components that influence flexibility?
Welcome to Huberman Lab Essentials, 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.
Chapter 2: How do Golgi tendon organs affect muscle load sensing?
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 weaved 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.
Chapter 3: What are the different types of stretching methods?
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 by way of changing the length of the muscle, adjusting the function of connective tissue like tendons and ligaments.
Chapter 4: How can static stretching protocols improve flexibility?
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
Chapter 5: What role does warming up play in effective stretching?
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.
Chapter 6: How does aging impact static stretching and flexibility?
And we have these spindles within the muscles themselves that wrap around the muscle fibers.
Chapter 7: What is the Anderson Method for stretching?
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 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 safe range again.
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.
Chapter 8: How can stretching enhance pain tolerance and relaxation?
It actually doesn't really shorten the muscle, but it contracts the muscle that 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,
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 and it 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 call 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.
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