Improve Flexibility with Research-Supported Stretching Protocols

welcome to the huberman Lab podcast where we discuss science and science-based tools for everyday [Music] life I'm Andrew huberman and I'm a professor of neurobiology and Opthalmology at Stanford school of medicine today we are going to discuss the science and practice of flexibility and stretching flexibility and stretching are topics that I believe do not receive nearly as much attention as they deserve for most people the topics of flexibility and stretching bring to mind things like yoga injury prevention or maybe even contortionism but it turns out that flexibility and stretching are features that are built into our basic body plan young children young animals and adults and indeed older children and animals all stretch and all have some degree of flexibility it turns out that having flexibility and our ability to stretch and the interaction between stretching and flexibility are fundamental to how we move our ability to learn new movements indeed also to prevent injury or repair injuries and to offsetting and reducing inflammation throughout the body in fact today I'm going to share with you a remarkable set of studies that show that stretching can actually adjust things like tumor growth this is work that was done by one of the major directors of the National Institutes of Health so today's discussion will start with a description of the mechanisms literally the cells and the connections from your nervous system that mediate flexibility and stretching and I promise that I'll make that information accessible to you whether or not you have a biology background or not then with that information in hand I'm going to present to you what the scientific literature says about the best times and ways to stretch everything right down to the detail of how long to hold a stretch whether or not to hold a stretch at all because it turns out there are multiple kinds of stretching so you can imagine you have stretches where you hold the stretch for a very long time and use as little momentum as possible and then there's also what's called Dynamic and ballistic stretching where you're literally swinging your limbs trying to increase the range of motion I will explain the science and application of flexibility and stretching in the context of sports performance whether or not you're engaging in cardiovascular exercise or resistance exercise or both whether or not you're competitive athlete or simply a recreational exerciser as I am whether or not you are trying to increase your range of motion and flexibility for longevity purposes or whether or not you're trying to do it in order to access different parts of your nervous system because we'll soon learn today that your ability to improve flexibility anded to engage in specific stretching exercises can actually be used to powerfully modulate your ability to tolerate pain both emotional and physical pain so this thing that we call flexibility and stretching is actually a vast landscape we're going to simplify and organize all that for you today and by the end of today's episode you're going to have a number of simple easy to apply tools that are grounded in the best scientific research that you can apply for your specific goals before we begin I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford it is however part of my desire and effort to bring zero cost to Consumer information about science and science related tools to the general public in keeping with that theme I'd like to thank the sponsors of today's podcast our first sponsor is thesis thesis makes custom neut Tropics that are designed to get your brain and body into the optimal State for the cognitive and physical things that you need to perform at the highest level I have to confess in fact I've said it many times before I am not not a fan of the word neut tropics because it means smart drugs and frankly as a neuroscientist I'd be remiss if I didn't acknowledge that there's 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out the propod cover and save $150 at checkout eights sleep currently ships within the USA Canada and the United Kingdom again that's 8sleep.com huberman to save $150 at checkout let's talk about flexibility and stretching before we talk about the practices of flexibility and stretching I'd like to just just highlight some of the features that are already built into your nervous system and into your body that allow you to be flexible some of us feel tighter than others sometimes in specific limbs or areas of our body some people feel really loose and limber some people even have what's called a hyper flexibility I for instance have a relative that can take her fingers and bend them back to the point where they touch her wrist and it always uh you know makes me cringe a little bit but she can do that without any pain she seems to have some hyper flexibility in her joints I do not have that feature some of you may find that you are more flexible than others naturally and some of you might be thinking you don't need to build in additional flexibility well I think by the end of today's episode you'll realize that almost all of us can benefit from having some sort of understanding about flexibility and having some stretching protocol that we incorporate into our life if not just for physical performance reasons and for postural reasons then also for cognitive and mental reasons and I'll be sure to clarify what all of that means right now I'd like to take a moment and just highlight the flexibility that you already have for instance if you were to move your arm behind your torso a little bit and then sort of let go or stop exerting any effort in doing that you would find that the limb would return more or less to a position next to your torso at least I would hope so now why is that well it turns out that there are aspects of your nervous system aspects of your skeletal system system aspects of your muscles and aspects of the connective tissue that binds all of that together that try and restore a particular order or position to your limbs and your limbs relative to one another so that reflects a very specific set of processes that it turns out are the same set of processes that you use when you are trying to enhance flexibility and stretching so i' like to just take a moment and review the basic elements of nervous system muscle connective tissue and skeletal tissue bone that allow for flexibility and stretching and here we can point to two major mechanisms by which your nervous system neurons meaning nerve cells communicate with muscles and those muscles communicate back to your nervous system to make sure that your limbs don't stretch too far they don't move too far such that you get injured and in addition to that mechanisms that ensure that you don't overload your muscles too much with weight or with tension or with effort and damage them that way because it turns out that the second security mechanism of making sure that you don't overload muscles can be leveraged toward increasing your flexibility almost immediately that's right there are protocols and tools that I'll share with you that are going to allow you to vastly improve your flexibility over time but there are also mechanisms that allow you to quite significantly increase your degree of flexibility in a very short period of time within just a few seconds so let's establish some of the basic biological mechanisms anytime we talk about biology or physiology we're going to talk about structure meaning the cells and their connections and functions what they do there just a few names to understand you do not have to memorize these names 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 some of you may have heard of fascia we're going to talk a little bit about fascia today although it's such an interesting tissue that's really deserving of its own episode fascial tissue we're going to talk about some of the stuff that surrounds muscles that really gives you your shape and holds everything together and allows for flexibility to occur 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 to be precise they are lower motor neurons because they're in your spinal cord we call them lower to distinguish them from the motor neurons that are in your brain up in your skull those lower motor neurons Hereafter I'll just refer to them as motor neurons if I want to talk about the other kind of motor neurons I'll say upper motor neurons so if I say motor neurons I just mean the ones in your spinal cord those motor neurons send a little wire or set of wires out to your muscles and that creates what's called a neuromuscular Junction which just means that the neurons meet the muscles at a particular place those neurons release a chemical that chemical is called acetylcholine some of you may have heard about acetylcholine before acetylcholine also exists in your brain and does other things in your brain mainly it's involved in focus and attention but at the neuromuscular Junction 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 and for instance if you're bringing your wrist closer to your shoulder that biceps muscle is Contracting it's getting shorter I mean in reality it hasn't gotten shorter overall it's just temporarily shorter of course all of that is controlled by neurons and it's those motor neurons from the spinal cord that are really responsible for the major movement of your limbs by way of causing contraction of specific muscles at specific times so the key thing to take away is is that nerve controls the contraction of muscles 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 the sensory neurons exist in a different part of the spinal cord and they send a little wire or set of wires into the muscles and there's a particular kind of sensory neuron that comes out of your spinal cord and into your muscles which are called spindle neurons they create or they actually wrap around muscle fibers kind of cork screw around them and give it kind of a spring-like appearance if for you afficionados out there these are intrafusal connections or neurons intrafusal means within the muscle but you really don't need to know that unless you're really curious about it or you're going to become a neuroscientist or you're in medical school or something 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 much in the same way that you have neurons in your eye that sense light in your external environment you have neurons in your ear that sense sound waves in your external environment you have neurons in your spinal cord that are sensory neurons that are sensing the amount of stretch in the muscles what happens is if a given muscle is stretching really far those Sensory neurons those spindles within the muscle will activate and will send a electrical potential literally a bit of electricity along that wire's length into the spinal cord and then within the spinal cord that sensory neuron communicates through a series of intermediate steps but to the motor neuron and make sure that that motor neuron contracts 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 safe range again now what determines whether or not a range of motion is quote unquote safe or not is dictated by a number of things it's dictated by things that are happening in this kind of loop of neural Connections in the spinal cord and muscle it's also determined by what's going on in your head literally in your mind cognitively about whether or not the movement of that limb it's increasing range of motion is good for you whether or not you're doing it deliberately whether or not it's bad for you and then there are also some basic safety mechanisms that are put in there that really try and restrict our limb range of motion 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 of which there are a bunch of different varieties of in this case what we're calling the 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 that brings the limb back into a safe range of motion okay so this process is very fast it was designed to keep your body together and safe it's designed to make sure that you don't you know take your arm and swing it behind your torso and it just goes all the way back to the middle of your back I mean unless you're a contortionist if you've trained that kind of level of flexibility that would be terrible because it could provide a lot of damage to the muscles and to the connective tissue and so forth 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 this other mechanism has a lot of the same features as the one I just described but it has less to do with stretch in fact it doesn't have to do with stretch as much as it 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 GGI 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 and you start to try and heave that weight off the ground 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 it could tear ligaments well you have a safety mechanism in place it's these GGI tendon organs these GTO as they're called that get activated and shut down the motor neurons and make it impossible for those muscles to contract okay so on the one hand we have a mechanism that senses stretch and can figure out when stretch is excessive and when this system detects that stretch is excessive it activates the contraction of muscles and then we have a second mechanism that senses loads and when tension or loads is deemed excessive by these circuits and remember these circuits don't have a mind they don't go oh this is excessive they just sense loads and when those loads exceed a certain threshold well then those GTO those Gog tendon organs send signals into the spinal cord that shut down your motor neurons ability to contract muscle so that you no longer can lift that heavy load so both of these are protective mechanisms but both of these can be leveraged in a very logical way and in a very safe way in order to increase your limb range of motion so there are a couple things I want to point out before going a little bit further into how your nervous system controls flexibility and stretching and those key points are the following there are now dozens if not hundreds of studies that show that a dedicated stretching practice can improve limb range of motion now for many of you listening you're probably saying duh but I think it's important to point that out that a dedicated stretching practice can increase limb range of motion and as you'll soon learn there are specific mechanisms that can explain that effect the second point is one of longevity and when I say long vity I don't necessarily mean late stage aging we all undergo a decrease in limb range of motion unless we do something to offset that decrease and the current numbers vary from study to study but if you look in Mass you look at all of those studies and what you basically find is that we start to experience a decrease in flexibility from about age 20 until about age 49 that's pretty dramatic and then of course it will continue after age 49 but basically it's a 10 % decrease every 10 years so we could say it's a 1% decrease per year although it's not necessarily linear what do I mean by that well it's not necessarily that on your 21st birthday you are 1% less flexible than you were on your 20th birthday and it decreases by 1% per year some of these changes can be nonlinear so you can imagine the person who's doing just fine in terms of flexibility between 20 and 30 and then you know they get to 32 and suddenly they've lost 5% of their flexibility now of course there will be a ton of Lifestyle factors if you're a regular practitioner of yoga if you have a dedicated stretching practice if you're doing other things to improve your muscle contract ability so you're doing resistance training it turns out can actually indirectly improve flexibility there are a number of different factors but the key point is that maintaining some degree of flexibility and maybe even enhancing range of motion and flexibility is of immense benefit for offsetting injury provided it's not pushed too far there are a number of people who have pushed their limb range of motion so far that they experience all sorts of injuries both acute and chronic injuries today we'll also talk about how to avoid those scenarios Okay so we've established that there are mechanisms within the spinal cord muscles and connective tissue those remember it's the motor neurons the spindles the GTO and of course the muscles themselves and connective tissue tendons but also other forms of connective tissue that establish whether or not a limb is going to stay within a particular range of motion or not and whether or not a limb is going to be allowed by the nervous system to pursue or handle a given load a given tension 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 that's actually you know kind of feeling I feel great I feel sated I feel relaxed those are all different forms of interoception the main brain area that's associated with interpreting what's going on in our body is called the insula I NSU 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 and to some extent other things that are arriving from the external world and combining with what's going on internally and making sense of that of all that or at least routing that information elsewhere in your nervous system to make decision like if you smell something good to approach it or if you smell something bad to avoid it the front of the insula is really doing all of that kind of stuff along with other brain areas 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 and how is the movement that you happen to be doing combining with your internal state to allow you to feel as I like to say the nervous system mainly batches things into yum like oh this is really good for me yuck this is really bad for me and I need to stop or meh this is kind of neutral okay so this isn't about food but we could say for most stimuli most senses whether or not they're senses of things internally or externally our nervous system is trying to make decisions about what to do with that information and so 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 and then meh so if it doesn't really matter I can just kind of stay right here we not yum yuck and meh well in your posterior insula you have a very interesting population of very large neurons these are exceptionally n large neurons called van eono neurons these are neurons that are again unbeknownst to most neuroscientists and they seem uniquely enriched in humans chimpanzees have them and other large animals have them so they're found in whales chimpanzees elephants and in humans but even though we are much smaller than most whales and even though we are much smaller than most elephants I mean remember there are baby elephants as far as I know they haven't breed up um like like mini elephants yet they seem to have a a teacup version of pretty much every dog breed um you can look that up I don't I certainly have mixed feelings about this notion of of trying to downsize everything to the point where you could kind of like the pocket sized Bulldog I think someday will arrive I'm not a fan of that kind of downsizing of of different breeds but because there aren't teacup elephants and teacup gorillas and teacup chimpanzees and so forth most all of those other species are larger than us they have these van Economo neurons and we have these van Economo neurons but we have in upwards of 880,000 of these things in our posterior insula these other species tend to have somewhere in the range of a th000 to maybe 10,000 or so why is that interesting well these van Econo 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 p specific goal this knowledge turns out to be very important to keep in mind because as we migrate this conversation toward the things that we can do to enhance flexibility and stretching you'll soon learn that there are moments within a stretching protocol where you have the opportunity to either override pain and discomfort to kind of relax through it or push through it right there's a decision fork in the road there and I'll tell you which fork in the road to take or to say uh-uh I'm not going to do that I'm going to allow these natural reflexes of the spindle to kick in and just essentially stop me from stretching if a given limb isn't designed or shouldn't be stretched that far so I'd like you to keep these van eono neurons in mind I should mention they're named van eono because the guy Constantine ven eono that discovered them at the end of the 1800s early 1900s decided to name them after himself as many scientists do or certainly the neurologists and and Physicians are famous for naming things after themselves these van eono neurons turn out to be very important to keep in mind as we embark on our exploration of what sorts of stretching practices can be best applied to increase flexibility because whether or not you undertake a mild moderate or intense flexibility training you will no doubt encounter a scenario at some point where you will have to ask yourself do I quote unquote relax in into this stretch or do I try and push through just a little bit of discomfort and I'll explain how to gauge that decision in a very specific and ideally safe way and I'll give you some tools that will allow you to make that decision in the way that best preserves the Integrity of those neural circuits that I described earlier and can keep you safe these van eono neurons sit in the exact position that one would want to be able to evaluate what's going on in the body in particular what's going on in terms of limb movement ments how that relates to our feelings of discomfort and then there's the other aspect of these van aono neurons which is that these van eono 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 and stress to one of so-called parasympathetic activation to one of relax relation often times 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 these vancon neurons sit at this Junction where they're able to evaluate what's going on inside our body and allow us to access neural circuitries by which we can shift our relative level of alertness down a bit or our relative level of stress down a bit and thereby to increase so-called parasympathetic activation and to literally override some of those spindle mechanisms even the GTO mechanisms but especially the spindle mechanisms at the neuromuscular and muscular spinal Junction and in that way gently subtly override the reflex that would otherwise cause us to contract those muscles back the reason that's possible is because your brain has those other kinds of motor neurons the upper motor neurons that can both direct meaning control and can override lower motor neurons I'll give you a brief example of this that you've already done in your life and that we all have the capacity for what I'm referring to is the monosynaptic stretch reflex this is something that every first year Neuroscience graduate student learns which is that if you were to step on a sharp object with a bare foot you would not need to make the decision to retract your foot you would automatically do that provided you have a healthy nervous system there are mechanisms in place that cause the retraction of that limb by way of ensuring that the proper muscles contract and other muscles do not contract in fact that they fully relax okay so in the case of stepping on a sharp object like a piece of glass or a nail or a attack you would essentially activate the hip flexor to lift up your foot as quickly as possible in doing so that that same neural circuit would activate a contralateral meaning opposite side of the body circuit to ensure that the leg the foot that's not stepping on the sharp object would do exactly the opposite and would extend to make sure that you don't fall over all of that happens reflexively it does not require any thought or decision making in fact humans without any neocortex literally that who are desate or or an animal that doesn't have and when I say desate I mean lack of cerebral cortex they can perform that because it's all controlled by circuits that are basically below the brain and in the spinal cord there's a little bit of activation of circuits in the kind of deeper parts of the brain but basically you don't need to think or decide in order to do that however if your life depended on walking across some sharp objects let's say um let's make it a little less dramatic so it's not like the diard movie or something where he has to run Barefoot across the glass although that's a pretty good example of what I'm describing here but let's say you had to walk across some very hot stones to get away from something that you wanted to avoid you could override that stretch reflex by way of a decision made with your upper motor neurons your insula and your cognition and almost certainly those van eono neurons which would be screaming don't do this don't do this don't do this could shuttle that information to brain areas that would allow you to override the reflex and as essentially push through the pain and maybe even in fact even not experience the pain to the same degree or even at all so these van eono neurons sit at a very important Junction within the brain they pay attention to what's going on in your body pain pleasure Etc and that includes what's going on with your limbs and your limb range of motion they also are paying attention and can control the amount of activation kind of alertness or calmness that you are able to create within your body in response to a given sensory experience and as I mentioned before they seem to be uniquely enriched in humans they seem to be related to the aspects of our Evolution that allow us to make decisions about what to do with our body in ways that other animals just simply can't before we go any further I want to give you a practical tool that you can of course use but that will also give you insight and experience into your muscle spindle spinal cord circuit mechanisms so what I'd like you to do is if you're in a proper place to do this you're going to stand with legs straight meaning knees Not Bent and you're going to try and touch your toes or for some of you that's going to be very easy and you might even be able to put your hands flat on the floor I don't have that kind of flexibility it's pretty easy for me to touch my toes I don't care if you round your back or not although ideally I would say don't round your back not because it's bad to do so necessarily but just to try and keep this uh the same from trial to trial as it were so try and get a sense of what your range of motion is in terms of bending over um at the waist while maintaining a flat back and trying to touch your toes or even touch the floor maybe again you can even go hands flat to the floor maybe even far out in front of you okay now what I'd like you to do is stand back up and I'd like you to contract your quadriceps as hard as you possibly can for about 5 to 15 seconds let's say 10 seconds just to keep things more or less normalized this obviously is not a super controlled experiment so to contract your quadriceps for those of you that don't know you're going to extend your lower limb out so this would be like kicking although don't do it too quickly you're going to kick out your uh your foot um you should feel your quadriceps contract on the top of your thighs and you're going to try and consciously contract them as hard as you can okay typically uh if you want to point your toe back towards your knee or Shin that's also going to help somewhat to contract even harder and harder okay so do that for about 10 seconds a lot of you will do this just while standing contract contract contract okay then release it and then now go ahead and repeat that stretch where you're trying to touch your toes or touch the floor so this is again relying more or less on hamstring flexibility among other things okay what most of you will find is that you have an immediate increase in hamstring flexibility or your range of motion has increased if you didn't experience that then I would encourage you to try and contract your quadriceps harder and longer so maybe 20 or 30 seconds and then try this so-called experiment again why would Contracting your quadriceps allow your hamstring flexibility to suddenly increase well the way that our muscles are organized is such that we have muscles that are antagonistic to one another so our quadriceps and our hamstrings work in sort of a pushpull fashion if you will they can antagonize one another so when you move your heel towards your glutes you are using your hamstring the hamstring obviously also does other things related to hip movement and when you lift your knee or when you extend your foot and contract your quadriceps you are essentially relaxing the hamstrings now of course most movements involve both quadricep and hamstring in synchrony and that synchrony is really an elegant one but here we're more less isolating the quadriceps from the hamstrings at least to the extent that it can leverage these spindle stretch mechanisms so what happens is when you contract your quadriceps hard you are relaxing or releasing some of the stretch that's occurring in those intrafusal spindle sensory fibers going into your spinal cord and as a consequence you're able then to stretch your hamstrings further or we can be more accurate and say that your range of motion about the hamstring and its related joints is greater when you aren't engaging that spindle reflex which would cause the hamstrings to contract okay so if you are somebody who has tight hamstrings there could be a variety of reasons for that but part of the reason is likely to be neural and you can release that neural spindle reflex by Contracting the opposite antagonistic muscle which in this case is the quadriceps the same thing it is true and can be leverage for stretching other muscles so for instance if you're going to do a tricep stretch the typical kind of overhead where you grab your elbow and you know move it toward the midline of your body with the other uh using your opposite hand well you can do that and then I would suggest trying to flex your bicep contract your bicep that is while doing that and for most people you'll notice a increase in the tri BP range of motion or ability to kind of lean into or to relax into or to push that stress stretch excuse me a little bit further now for you physios out there and for those of you that have backgrounds in kinesiology I want to acknowledge of course there are other mechanisms that are coming into play there are actually neural connections within the joints themselves that are providing propri receptive feedback etc etc but this is simply to illustrate that part of our range of motion is determined by these spindle mechanisms that I spent some time uh focusing on earlier and indeed this approach can be leverage toward creating increased limb range of motion not just for the hamstrings but for your quadriceps so for instance if you have tight quadriceps you can do the opposite you can contract your hamstring very intensely for let's say 10 seconds or 20 seconds or 30 seconds so that would take some conscious effort of bringing your heel up towards your glute glutes um you could do that in a way that you're really trying to contract those muscles hard you'd have to use some deliberate hamstring activation there meaning you have to use those upper motor neurons and the other aspects of your your upper brain power as it were to try and really contract your hamstrings as intensely as possible then you would relax that and then you would do your quadricep stretch again and if you did a preh hamstring contraction measurement of your quadricep flexibility and then you did a post hamstring contra action measure of your quadricep flexibility almost certainly you would find that that flexibility had increased now of course the muscle really didn't change much the tendons didn't change much what changed was the patterns of neural activation that were restricting you from in the first case stretching your hamstring or having a to be more accurate we should say to having a certain range of motion about the hamstring and its related joints and those break mechanisms were removed and of course that when you contract your hamstring you're removing some of the neural brakes the spindle acting as a break and inhibiting that quadricep range of motion okay so you can imagine this and in fact you can apply this for any number of different muscles the larger muscles and the sort of biceps triceps and uh hamstrings quadriceps are sort of the simplest place to think about this and to apply it but in theory and indeed in practice it really works for all the various muscle groups It's just sometimes harder to access these so-called antagonistic muscle groups now we should take a moment and just discuss what actually happens as we get more flexible in the short term and long term I just mentioned what happens in the short term clearly those don't involve lengthening of the muscles it's not like the muscles slide along the bones or that the tendons really stretch out that much more than they had prior to that kind of uh you know exercise but it is the case that if people stretch consistently over a given period of several weeks or more that there are changes in the muscles this gets a little bit tricky in terms of Gomen clature and I just want to highlight that because I think that a number of people um get frustrated uh and Confused in fact when we talk about muscles getting longer you know that the whole concept of a muscle getting longer isn't really in keeping with reality but there are elements within the muscles that can change their confirmation so to get a little bit detailed here and we won't spend too much time on this but I just want to acknowledge this for those of you that are interested in neuromuscular physiology and how it relates to flexibility you know you have your muscle fibers and then you have your so-called myofibrils so you can imagine kind of a a single fiber um that fiber of course will get input from those motor neurons and then within those fibers you have what are called sarir and you can kind of think about sarir as little segments kind of like the segments of bamboo if you ever look at bamboo it's not just one big stock it's got those little outpouchings along the way that um going to break up the what would be just one big stock of bamboo into different segments but they're all connected the sarom mirors are somewhat like that and within the sarom mirors you have a couple of different components one thing is called mein which is like a thick layer and then the other is actin and those are interdigitated as we say they're kind of connected to one another kind of like if you were put your your fingers together from your two hands um if you're going to put your fingers between one another that's interdigitated literally interdigitated in this case so pun intended and the myosin and actin kind of move relative to one another and they have a lot to do with your ability to contract muscles when we stretch muscles when we go through a stretching practice there are a number of things that change some neural some related directly to connective tissue but also it appears from really nice work mainly done from McGill University I'll provide a link to a couple studies if you want to dig in there deep more deeply that change the confirmation the relative size and spacing of some of these things like sarir and the way that masin and actin kind of work together but we don't want to think of muscles as lengthening we can however think about the resting state of a muscle being slightly different or indeed very different than the resting state of a muscle of somebody or of a limb that has not undergone regular flexibility training so that's as much time as I want to spend on that because we could spend an entire hour getting right down into the details but I do want to emphasize however that muscles have different parts they have fibers they have sarcom they have myosin they have actin but the idea of making our muscles longer that reflects a number of processes that occur basically within an existing muscle length our the length of our muscle bellies and where our insertions are uh relative to our connective tissue and our limbs is genetically determined right some people have for instance a bicep that goes all the way from the crook of their elbow up to their shoulder right um and some people can you know if they were to put their arm at a 90° angle could put two or three fingers between their bicep and their elbow they have a we can say a shorter bicep relatively shorter now the reason I mention these highly detailed cell mechanisms is because as we start to embark on different protocols for using stretching to increase flexibility in range of motion we need to ask ourselves what is preventing our ability to extend range of motion is it the spindle right is it because the muscle is stretching too much often times it can be because of that Andor because of a sense of pain or simply a sense that the muscle is not in a position that it's been in before that's unrelated to pain or to spindle activation and often times it can be related directly to these changes in the confirmation of mein and actin and within the context of the sarom mirors now of course you can't peer into or sense your individual sarir however you do have neurons that innervate these areas and that send that sensory information back into the spinal cord and up to your brain to interpret so you'll find that as we move along there are specific adjustments that you can make at both the macro level meaning how much movement to insert into your stretching right is is it going to be a static or a dynamic or even a ballistic stretch or for instance at the micro level that even just a slight submillimeter or millimeter increase in the stretching of a given muscle and it related tissues can translate into an increased range of motion performance as a quick but relevant aside I thought I'd share with you something useful that's also grounded in this notion of antagonistic muscles so for those of you that do resistance training whether or not it's with body weight or with physical weights or machines what have you you may have found that if you let's say were to do three sets of a pushing exercise so this could be push-ups uh this could be bench presses this could be shoulder presses something of that sort and then later in the workout you were to do let's say machine pull Downs or pull-ups or chinups of some sort so a pulling exercise typically what you would find is if you were to do what's often called straight sets so you would do three sets of push-ups let's say with 2 minutes of rest in between that you might be able to get a certain number of repetitions on the first set just for sake of example let's say you can get 10 repetitions on the first set and then you get eight repetitions on the second set and then you get six repetitions on the third set with two minutes in between and then you would move on at some point to your pulling exercises and similarly let's say you were doing chin-ups or pull downs and you would get 10 repetitions rest two minutes eight repetitions rest 2 minutes and six repetitions okay fine well typically what people discover is that if they inter leave their pushing and pulling exercises provided they do that for muscles that are antagonistic to one another so in this case pushing with the chest shoulders and triceps for the pushing exercises and pulling with the back and biceps and of course there other muscles involved as well but because those muscle groups are at least in part antagonistic to one another what people often find is that if were to say do their pushing set get 10 repetitions then move to a pulling set after just say 60 seconds and perform that pulling set then go back to the pushing set then go back to a pulling set Push Pull Push Pull in other words interleaving their sets even if they were to maintain the same amount of rest between sets of pushing and sets of pulling what they discover often is that the drop in the number of repetitions that they get is somewhat offset so rather than get 1086 as it were with the straight sets it will be 10 9 8 so what this means is not that you're increasing the total rest time to four minutes between sets because then of course it wouldn't be uh equivalent but rather that while maintaining the same amount of rest between sets for this same muscle Group by going from Push Pull pull Push Pull of antagonistic muscles you're able to have improved performance and the reason for that has everything to do with what we were describing before which is that typically if you were to do push set rest push set rest push set rest well in between those sets and in fact actually during those sets of pushing the pulling muscles that would be involved in the chin UPS or pull Downs Etc are actually relaxing or at least are being released of some tension including the activation of the spindles among other things so that's a long-winded way of saying the interleaving push and pull of ant antagonistic sets can leverage some of the same neural circuits that we're talking about leveraging for sake of increasing flexibility now I offer this to you as a tool that you can try uh one of the challenges with using this tool however is that you often have to occupy multiple sites within the gym um you know if you're doing this at at home and you have your own gym that's one thing if you're doing this in a gym where you have multiple pieces of equipment well then you become that person who has essentially taken over some small corner or multiple corners or machines within the gym and often times you'll find that you'll walk back to a machine or you'll walk back to a given resistance exercise and someone has now taken it over and the whole thing can be thrown off so it takes a little bit of orchestrating uh in order to do properly but in general what people find is that this can allow you to enhance performance overall of these individual movements again while maintaining the same amount of rest and even if you choose not to do this I encourage you to pay attention to this as a concept because again it's leveraging this idea of antagonistic muscles flexors and extensors antagonistic neural relationships between the spinal cord mechanisms that control one set of muscles and activating those muscles allowing the opposite antagonistic muscle to relax and therefore to perform better on its next set so now I'd like to shift to the question of what types of stretching can and should we do to increase limb range of motion if our goal is to do that in the most efficient way possible because I realize that most people don't have endless amounts of time to dedicate to a stretching practice and even for those of us that do I'm sure that you want to get the most outcome for a given effort and what are the modes of stretching that are going to allow us to increase our flexibility and limb range of motion most safely now there are a number of different types of stretching or methods of stretching broadly defined we can describe these as Dynamic ballistic static and what's called PNF stretching PNF stands for propri receptive neuromuscular facilitation and it involves and leverages many of the mechanisms that I described to you earlier the first two that I menion Dynamic and ballistic stretching both involve some degree of momentum and can be distinguished from static and PNF type stretching now to distinguish Dynamic stretching from ballistic stretching like to focus on this element of momentum both involve moving a limb through a given range of motion in Dynamic stretching however it tends to be more controlled less use of momentum especially towards the end range of motion whereas in ballistic stretching there tends to be a bit more swinging of the limb or use of momentum so I invite you to visualize what dynamic and ballistic stretching might look like in your mind you can even try it if it's safe for you to try it know you could imagine you know swinging your arm up overhead as much as possible and bringing it down I'm doing this because I'm seated is kind of ridiculous movement to do well seated or perhaps at all but for instance you can see Dynamic and ballistic stretching anytime someone for instance is holding on to something with one arm or maybe not holding on and Swinging out their their foot so essentially getting movement about the hip joint and you'll notice that some people raise it up and pause it and bring it down that's one form of dynamic stretching whereas others will swing it up and sort of Let It carry itself a bit further due to the momentum at the top of the movement and then just let it drop back down or maybe even control The Descent there is an enormous range of parameter space here or variables that one could imagine and there's just simply no way that we could subdivide all those but again Dynamic and ballistic stretching both involve movement so we have to generate some force in order to create that movement ballistic stretching involving a bit more momentum or sometimes a lot more momentum especially at the end range of of motion now both of those are highly distinct from static stretching which involves holding the end range of motion so minimizing the amount of momentum that's used so to stay with a simple example that we are all now familiar with from our earlier discussion slowly bending over at the waist and trying to touch your toes or putting your hands to the floor and then holding that end position before coming up in a slow and controlled way such that you reduce the amount of momentum to near zero would be one example of static stretching static stretching can be further subdivided into active or passive right there are different names for these kinds of approaches you can hear about the Anderson approach or the Jer approach you can look these sorts of things up online and again again people tend to name things after themselves so some of these are proprietary related to specific programs I'm not focusing on those others come to be named after the physiologists or the practitioners that initially popularized them as is always the case there's always a naming and renaming and claiming of territory with these things for the time being I'd like to just emphasize that static stretching can be both active where there's a dedicated effort on the part of the stretcher you to put forth behind the hold to kind of extend or literally to extend the range of motion and then there's also passive static stretching in which it's more of a relaxation into a further range of motion and that can be a subtle distinction and there are other ways in which we can further distinguish active and passive static stretching but nonetheless static stretching involves both those types of elements active and passive but is really about eliminating momentum and then there's the p F the propr receptive neuromuscular facilitation and propri reception has several different meanings in the context of Neuroscience and Physiology to just keep it really simple for today propri reception involves both a knowledge and understanding of where our limbs are in space and relative to our body typically relative to the midline so the brain is often trying to figure out where are our limbs relative to our midline down the center of our body and we know where our limbs are based on so-called proprio receptive feedback so that's feedback that comes from Sensory neurons right now you know what Sensory neurons that are essentially monitoring or responding to events within the joints the connective tissue and the muscles and within the Deep components of the muscles like the spindle reflex and within the tendons like the GTO the GGI tendon organ so PNF type stretching leverages these sorts of mechanisms these these neural circuits by way of for instance you would lie on your back and if your goal is to increase your hamstring flexibility and the flexibility and range of motion of other related muscle systems you might put a strap around your ankle and pull that muscle or I should say excuse me that limb towards you you're not going to pull the muscle towards you you're going to pull that limb your ankle towards you trying to get it sort of back over your head and then progressively relaxing into that or maybe even putting some additional Force to push the end range of motion and then relaxing it and then actually trying to stretch that same limb or increase the limb range of motion without the strap right sometimes these are assisted by other people so people will even use loads sometimes they'll even use machines uh there are a number of different um apparati that have been designed for this sometimes it'll involve a training partner there's a huge range of PNF protocols and those protocols calls can be done both by oneself with or without straps with machines with actual weights or with training Partners if you're interested in the variation of exercises to say Target your hamstrings versus your quadriceps versus your shoulders versus your chest muscles Etc your neck muscles and so on there is an enormous range of information on Dynamic ballistic static and PNF stretches for all the various muscle groups and I should say there's some excellent books on those topics there are also some excellent videos on YouTube and elsewhere nowadays it's pretty easy to find exercises that allow you to Target specific muscle groups again I encourage you to be safe in how you approach this and I would encourage you also to pay attention to the information that soon follows as to what sorts of protocols one would use to apply those exercises but the number of exercises and the availability of those exercises for targeting different muscle groups with these four different kinds of stretching is both immense and fortunately thankfully immediately accessible to all of us often at zero cost so specific exercises to Target specific muscle groups aside we've now established that there are four major categories of stretching or at least those are the four major categories I'm defining today and we can further divide those categories into which are the ones that are going to be most effective for increasing range of motion in the long term not just in one individual session and there have been a number of studies exploring this I can list out at least four and we'll put those four as a kind of a cluster under one heading in the show note captions that arrive at essentially the same answer which is that for increasing limb range of motion it does appear that static type including PNF but static type stretching is going to be more effective than Dynamic and ballistic stretching so at least to my mind this is good news why is it good news to me well while Dynamic and ballistic stretching can be immensely useful for improving performance of specific movements in particular in the context of particular sports like tennis or in sprinting or frankly for any sport they do carry with them a certain amount of risk because of the use of momentum so you don't need to be highly trained in order to perform them in fact there is a place and we will describe when one would want to apply dynamic or ballistic stretching I'll just give away for now I think that most physios out there and certainly the ones that I spoke to Dr Andy Galpin Dr Kelly starett and a few others point to the fact that doing some safe Dynamic and ballistic stretching prior to say a resistance training session or maybe even prior to a cardiovascular training session can be useful both in terms of range of motion effects and in terms of neural activation effects I don't want to use the words warm up because warming up is typically associated with increasing core body temperature as it should be but for engaging the neural circuits and becoming familiarized with the neural circuits that you're about to use in other movements while also increasing the range of motion of the joints involved in those movements so that you can perform them more safely and more confidently so I'm certainly not saying I want to repeat I'm certainly not saying that dynamic ballistic stretching are not useful they absolutely are but in terms of increasing limb range of motion in the long term of truly becoming more flexible as opposed to transiently more flexible static stretching which includes PNF appears to be the best route to go so if your goal is to increase your limb range of motion for a given muscle group or perhaps for all muscle groups although you can imagine that' be pretty tough I mean you're not going to spend time I could imagine working on your tongue muscle control or neck muscle control and every muscle control but most of us want to reduce so-called tightness in air quotes and increase limb range of motion for certain muscle groups and it appears that the best way to do that is going to be static stretching of some kind which raises the question of how often to do that static stretching and how long to hold those static stretches and we can also ask the question we should ask the question where to hold those static stretches is it always a good idea to hold those static stretches at the end or the point of maximal range of motion we're going to address that now there's some terrific science around this a slightly older study but nonetheless a powerful one because it provided a foundation for a lot of subsequent work which basically served to just confirm the answer they got here is a study from Bandy at all and the title of the study is the effect of time and frequency of static stretching on the flexibility of the hamstring muscles it's a study involving 93 subjects so 61 men 32 women ranging in age from 21 to 39 years a pretty broad uh demographic who had limited hamstring muscle flexibility here I'm paraphrasing and randomly aside to one of five groups so the four stretching groups stretch five days per week uh for six weeks the fifth Group which served as a control did not stretch the results clearly show that quote the change in flexibility appear to be dependent on the duration and frequency of stretching this is great this tells us that stretching uh for a given amount of time scales with the amount of limb range of motion Improvement that one will see there were many interesting findings within this study but the one that I'd like to highlight most is quote the results of this study suggest that a 30-second duration is an effective amount of time to sustain a hamstring muscle stretch in order to increase range of motion no increase in flexibility occurred when the duration of stretching was increased from 30 seconds to 60 seconds or when the frequency of stretching was increased from 1 to three times per day okay so now we're starting to lay down some parameters what this study reveals and what subsequent studies tell us and we will get into those subsequent studies is that ideally one would do static stretches that are held for 30 seconds perhaps more in certain instances and I'll explain when that can be useful but here holding those stretches for more than 30 seconds did not turn out to be additionally useful so if you're going to stretch your quadricep for instance and you're going to hold that stretch in static faction remember not using momentum and you can use the mental tricks of either trying to push through the pain which I don't recommend necessarily I think that makes us prone to injury or to relax into the stretch but nonetheless providing some Force typically with the with a hand in order you pull your ankle back if you're doing a quadricep stretch some people might do this on the edge of a sofa remember there are a lot of different exercises and ways to do this that you can explore elsewhere well holding that static stretch for 30 seconds appears to be sufficient to stimulate an increase in limb range of motion over time again these are protocols that were used repeatedly over time and we'll talk about how often to repeat them in order to get maximal effect but 30 second holds for static stretches is the number that I think we want to focus on and that most of us are are going to want to utilize so now let's explore how many sets of static stretching one ought to do in order to get a maximum range of motion Improvement while not placing us into a system that's going to create injury nor a situation where we have to be constantly stretching throughout the day because again most of us don't have time to do that this issue of sets is an important one in the context of cardiovascular exercise we've talked about the data that support the fact that doing at least 150 and ideally as much as 200 minutes per week of Zone 2 cardiovascular exercise is very useful for cardiovascular health and for other aspects of health and of course there are other aspects of cardiovascular exercise that could be layered onto and into that that can be useful like 90 second maximal Sprints Etc discussed this a lot in the episode with Dr Andy Galpin and on our episode about endurance and we also talked about sets in the context of strength and hypertrophy building building muscle size Andor strength in the episode about that and in particular in the episode with Dr Andy Galpin and there we could also arrive at some specific parameters and it's going to vary of course between individuals depending on how hard you train whether or not you take sets to failure your repetition range Etc but in the context of strength and hypertrophy building we arrived at a approximately six maybe as many as 10 sets per week per muscle group some of that work is done as direct work to a given muscle group some of that work is indirect so doing certain pulling EX exercise of course will Target the latissimus dorsy muscles but also the biceps so if you that doesn't necessarily mean you have to do 10 sets for the biceps and for the lats sometimes you're getting some indirect work etc all of that was delineated in the episode with Dr Andy Galpin and we arrived at those numbers of sets according to the same criteria that we will apply here what is the minimum number of sets both to maintain and to improve a given mode of performance strengthen hypertrophy or cardiovascular health again to either maintain or improve and we can do the same thing for improving or maintaining range of motion because as I mentioned earlier the data point to the fact that if we don't do some dedicated work to improve range of motion over time we will lose our flexibility and limb range of motion over time just by virtue of the fact that we're not doing anything to offset that so whether or not you want to maintain reestablish or gain limb range of motion static stretching of holds of 30 seconds appear to be best now the question is how long should you do that and how many sets should you do that and how many times a week should you do that and to answer those questions I'm going to turn to what I think is a really spectacular review this was a review that was published in the year 2018 so it's fairly recent first author Thomas it wouldn't Thomas last author Palma we'll put a link to this in the show note caption the title of the paper is the relation between stretching typology and stretching duration the effects on range of motion it's a very straightforward title this is a review article that explored a number of different studies had criteria for whether not those studies could be evaluated in the context of the questions here had some quality standards and some other standards that they applied and basically winnowed down a large collection of studies to a remaining 23 articles that were able to be considered quote eligible and included in the quantitative synthesis done here so key points from that quantification and synthesis done in this paper first of all and I quote all stretching typologies showed range of motion improvements over a longterm period however the static protocols showed significant gains with a P value less than .05 which means a probability that cannot be explained by chance alone when compared to ballistic or PN protocols so again what we're hearing is that static stretching is the preferred mode for increasing limb range of motion although here they make the additional point that static stretching might even be superior not just to ballistic stretching but also to PNF protocols because before as you may recall there was a distinction between ballistic and dynamic and static and PNF and so here it appears again that static stretching is sort of r ring to the top of the list as the optimal approach relative to all other stretching approaches at least in the context of increasing limb range of motion the authors go on to say time spent stretching per week seems fundamental to elicit range of movement improvements when stretches are applied for at least or more than five minutes per week okay this is critical this is not five minutes per stretch remember 30 seconds per static stretch but at least five minutes per week whereas the time spent stretching within a single session does not seem to have a significant effects for range of motion gains if this is getting confusing I'll make sure that you soon understand exactly what we can export from these conclusions the data indicate that performing stretching at least five days a week now some of you may already be groaning for at least five minutes per week okay so five days per week that's a lot but at least five minutes per week five minutes per week is not that much using static stretching may be beneficial to provote range of motion improvements okay I've read this study in detail now uh they highlight again the reduction in flexibility that occurs from 20 to 49 years of age and so on how acute bouts of short-term stretching up to three weeks can improve stretch tolerance I think that's a key point that in the short term the first three weeks of embarking on a stretching and flexibility program much of the improvements come from the short-term neural improvements that we talked about before of inhibiting the spindle ref flex and so on and also a stretch tolerance a comfort with doing the movements and maybe even a comfort in overriding some of the pain mechanisms I'll talk a little bit more about that in in just a bit and the particular utility of yoga something that I don't often practice but that after reading this article that I'll mention in a little bit I'm considering perhaps taking up some form of yoga protocol now I've already highlighted some of the key takeaways from the study namely that we need to get at least five minutes per week static stretching per muscle group and based on the previous paper that we talked about we need to divide that five minutes into sets of 30 seconds each and as I mentioned earlier it doesn't seem to be the case that you can do all of that in one day unfortunately it does seem important that the frequency of stretching practice distributed throughout the week is important so let's talk protocols we are now talking about doing static stretching so holding so limiting momentum and holding a stretch for 30 seconds per set we're talking about trying to achieve 5 minutes per week of those static holds but that we can't do it all in one session because the frequency of sessions distributed throughout the week correlates with the improvements in limb range of motion so what this means is that we should probably be doing anywhere from two to four sets of 30 second static hold stretches five days per week or some variant thereof and I do say some variant thereof because it turns out that even though there was that earlier study that we talked about that holding a stretch for more than 30 seconds in that case 60 seconds didn't turn out to be additionally beneficial it appears that if you do hold those stretches for 60 seconds per static stretching set for instance you can get away with stretching fewer days per week overall so in order to make the as clear as possible because I do realize there are a lot of parameters and you might be asking why didn't you just make me a list of the exact things I should do well it doesn't work that way because once you understand the mechanisms and once you understand your particular goals this information is designed for you to be able to construct a stretching program that is tailored to your specific goals if I just gave you the stretching program that I'm doing or I should say that I'm soon to be doing because I'm soon to be doing one based on the research for this particular episode well that wouldn't be beneficial for you because for instance if you have very flexible hamstrings but not very flexible quadriceps or you are somebody who is engaged in sport or not engaged in sport what you need to do is going to vary somewhat so what would effective stretching protocol look like we're all trying to improve limb range of motion for different Limbs and different muscle groups but just by way of example and it's because the one we've been using let's talk about hamstrings for the time being this could of course be applied to other muscle groups let's say you want to improve Pro hamstring flexibility and limb range of motion about and around the hamstring and involving the hamstring you would want to do three sets of static stretching for the hamstring again easy to find such exercises on the internet you would do that by holding the stretch for 30 seconds resting some period of time then doing it again holding for 30 seconds resting some period of time and then holding it for 30 seconds that would be one training session for the hamstrings I have to imagine that you'd probably want to stretch other muscle groups as well in that same session although at least as far as I could tell there were no data pointing to the fact that you couldn't do your hamstring stretching one part of the day and your quadricep stretching another part of the day but presumably you're going to want to combine your flexibility training in into one single session so three sets of 30 seconds each get 90 seconds and you would do that IDE five times a week or maybe even more because it does seem like frequency distributed throughout the week is an important parameter now one thing that we have not highlighted or at least described is how long to rest between stretching sets and despite my efforts I could not find research back information that pointed to whether or not 30 seconds of rest for every 30 second stretching or 60 seconds rest for every 30 second stretching was ideal I I think it's reasonable to assume that doubling the amount of time for the interleaving rest would be appropriate or at least doable if anyone out there has knowledge about rest between stretching sets and has some physiology or some biology or some experiential information as to why a given ratio of duration of static stretch to rest in between static stretch sets ought to be used please put it in uh the comments on YouTube that'd be a terrific way for us to get that information I'd love to do any followup to links that you provide and so on but now we're starting to build into a protocol that is backed by the scientific data three sets of 30 seconds of holds done five times or maybe even six times per week one thing that did show up in my exploration of the peer-reviewed research is this notion of warming up for all this we haven't talked about that yet in general to avoid injury it's a good idea to raise your core body temperature a bit before doing these kinds of stretches even these static stretches which we can sort of ease into and don't involve ballistic Movement by definition and the basic takeaway that I was able to find was that if we are already warm from running or from weight training or from some other activity that doing the static stretching practice at the end of that weight training or cardiovascular or other physical session would allow us to go immediately into the stretching session because we're already warm so to speak otherwise raising one's core body temperature by a bit by doing five to seven maybe even 10 minutes of easy cardiovascular exercise or calisthenic movements provided you can do those without getting injured seems to be an ideal way to warm up the body for stretching we should be warm or warm up to stretch although those warm-ups don't have to be extremely extensive and then just by way of logic doing the static stretching after resistance training or cardiovascular training seems to be most beneficial in fact and unfortunately we don't have time to go into this in too much detail today I was able to find a number of papers that make the argument that static stretching prior to cardiovascular training and maybe even prior to resistance training can limit our performance in running and resistance training I realize that's a controversial area you have those who say no it's immensely beneficial you have those who say no it inhibits performance and th those that say know it's a matter of how exactly you perform that static stretching and which muscle groups and how you're doing this and how much time in between static stretching and performance but to leave all that aside doing static stretching after some other form of exercise and if not after some form of exercise after a brief warmup to raise your core body temperature definitely seems like the right way to go now for some of you out there and I confess for me as well doing something five days a week seems like a big commitment even if that commitment is one to only do three sets of 30 second static stretches I say this because you've got the warmup I generally like to bring a kind of a focus and dedication to a practice and of course because when doing these kinds of protocols it's likely that you're not just stretching your hamstring so it's not just 90 seconds of work with a minute of rest in between but very likely that we also doing quadricep stretching and also doing stretching for the shoulders and stretching for the back and the neck and so on and so that entire session is going to take some time and 5 days a week is a pretty serious commitment for most especially for those of us that don't exercise or do athletics for a living which I don't so there is some evidence from the literature that one can get away with or I don't even know that we should think about as getting away with but that one can do longer hold static stretches of up to say 60 seconds but do fewer total sessions per week so rather than three 30second static holds doing 3 60-second static holds and doing those every other day and there really hasn't been a systematic exploration of this the article that I was referring to just a few moments ago um this analysis of the uh 23 articles was combined into this enormous uh set of tables and some um really quite nice graphs that you're welcome to look at um since we're going to provide a link to the study um there are a couple of key takeaways that I want to mention that are separate from this issue of how long to stretch and how often um first of all they describe in their discussion that there were improvements in range of motion independent of whether or not people did static stretching active stretching passive stretching ballistic stretching or PNF stretching so all of those forms of stretching will improve limb range of motion this is essential to point out and I want to emphasize this static stretching however gave the greatest degree of gains in Li range of motion and on average they saw a 20.9% increase but some of the other increases they observed were also quite substantial so ballistic stretching can also provide some pretty impressive limb range of motion improvements however they tended to be in the range of here they point out 11.65% increase or in the case of PNF a 15% increase so it appears that the greatest improvements in limb range of motion for your time spent and effort spent is going to be this minimum of 5 minutes per week to elicit a significant response with 5 days being the minimum weekly recommended frequency to achieve sign significant range of motion improvements I confess this was pretty surprising to me uh when I compare flexibility training to say resistance training for strength and hypertrophy I've had the experience and I know that other people have had the experience and I think uh Dr Andy Galpin uh would probably agree that provided one train hard enough and appropriately that you don't need to train resistance training 5 days a week in order to get significant improvements in strength and hypertrophy some people might need to but you can get a lot of positive results in those variables with less frequent training certainly with three or four days a week of training and for cardiovascular training I'm not aware of anyone having tested whether or not one very long run each week can actually increase cardiovascular fitness and you're not doing anything else although I have to imagine you'd probably see some improvement compared to not doing anything but most people are doing repeated training sessions of cardiovascular strength training not a lot of people are doing five days a week of strength training and at least that I'm aware of some people are but most people I think are not and some people are doing five or more days a week of cardiovascular training I'm guessing that most people are not doing 5 days a week of dedicated static stretch range of motion Direct training but it does appear that that frequency about the week getting those repeated sessions even if they are short for an individual muscle group turns out to be important and so that points to the perhaps the reason why so few people are doing dedicated range of motion work but it also reminds me that all of the studies that were described at least in this review and some of the other ones that were not really show impressive changes in limb range of motion I mean 20 plus percent or even 15% with PNF I mean these are big changes that are going to benefit us they're going to offset the age- related losses in flexibility for sure if one is dedicated about these practices and in many cases they're going to increase limb range of motion in ways that are going to allow us better performance in certain physical Endeavors certainly better balance right we haven't really talked about balance and stability but range of motion can impair balance and stability in some extreme circumstances but by and large limb range of motion lack of tightness improved posture imp improved physical performance excuse me and things of that sort is something that I think we can all benefit from and that are key features of longevity we don't often think of them because we so prioritize cardiovascular health and the relationship between the heart and brain health and resistance training and muscular skeletal uh hypertrophy or strength Etc but as I delved into this literature it really highlighted for me the extent to which having really good limb range of emotion at least maintaining limb range of motion as we age from year to year and maybe even improving limb range of motion can be immensely beneficial for reducing pain for again improving posture improving our ability to perform to walk Etc and indeed there's a whole literature that relates our limb range of motion to things like pain management of things related to headache and so on and so forth so limb range of motion is not just about becoming a contortionist or being able to complete the yoga class it really is about maintaining the integrity and the health of the neuromuscular system the connective tissue and the neuromuscular connective Network because those are indeed working as an ecosystem and a network I'd like to just briefly touch on PNF stretching for a moment again this is a vast landscape with many parameters and different practitioners a lot of uh competing opinions uh out there to put it lightly nonetheless I I do want to emphasize that the PNF training leverages those spindle mechanisms and GTO mechanisms that we talked about earlier but I realized that in describing the quadricep contraction hamstring stretch little mini experiment that hopefully you did that I didn't really highlight the role of the GTO the GG tendon organs that much and I just would like to just briefly do that for a moment the gto's have multiple functions in fact I think even though GTO are in every medical textbook every physiology textbook every first year neuroscientist learns about them when learning about the neuromuscular Junctions and the mechanisms of interoception Etc they're likely to have other functions as well and one of the reasons why PNF stretching does work whether or not you're doing that by using a strap to you know pull back a limb or whether or not you're actively Contracting your quadriceps to then release and emphasize stretch range of motion for your hamstrings and related muscle groups is is that activation of those GTO meaning putting loads and tension into that system can inhibit the spindles in the opposite antagonistic muscle groups okay so one of the reasons why flexing or I should say Contracting your quadriceps really intensely for some period of time allows your hamstrings to subsequently experience greater range of motion and again it's not just the hamstrings but the related connective tisue and neural circuits Etc is because yes it's quote unquote relaxing the hamstrings and the spindle but there's also a direct relationship between activation of the GTO in the quadricep and release of the spindles in the hamstring and related muscles this has a name it's called autogenic inhibition it's a fancy name for contraction of one muscle group providing relaxation of the other muscle group that's antagonistic to it and it relates back to this idea of interleaving sets in the gym so if you think back to that example now it should make sense as to why for instance if you do let's say a set of binge presses or shoulder presses and you let's say you get 10 repetitions and you fail on the 11th that muscle is very very fatigued if you were to rest some period of time and then go back and do another set well during the rest that muscle group has been relaxing it's obviously not Contracting the same way it was during the resistance set but by going and doing a pulling exercise that involves the antagonistic muscle group so strongly Contracting the back muscles through a pull like a a pull down or a chin up or a row type exercise you're activating or near activating the GTO system in those pulling muscles in a way that provides autogenic inhibition for the pushing muscles now again the physios out there are probably either screaming or banging their heads against whatever uh sound system this happens to be arriving through to them saying wait but in many cases the GTO aren't activated enough to provide that autogenic inhibition that's true but even the sub threshold activation of those intraspinal circuits so the place where the GTO circuit and the spindle circuit interact can provide an additional replenishment of say the pushing muscles while you're activating those pulling muscles and this is at least one not the only but at least one mechanisms by which interleaving push and pull push and pull for both strength and hypertrophy training but also for range of motion stretching type training can allow you to achieve better results in a shorter period of time and I raise this because I want to keep in mind the efficiency of any training program we just a moment ago established that doing for example three sets of 30 second static holds can be very useful for the hamstrings with let's just say for sake of Simplicity and practicality a minute's rest in between but during that minute's rest you can stretch the opposite antagonistic muscle group such as the quadriceps or if you want to use PNF training you could do loading of the quadriceps in between so there are a number of different ways in which you can start to interleave static stretching with PNF stretching you can start to interleave even PNF type protocols with resistance training although that gets a bit more complicated you can really start to construct and build protocols that are ideal for you what we will do is For an upcoming neural network newsletter so for those of you that aren't familiar the huberman Lab podcast has a so-called neural network newsletter these are monthly newsletters where we put distilled points from the podcast and oftentimes protocols in a downloadable PDF form you can access it by giving us your email we don't share your email with anybody if you want to see examples of these you can go to hubman and go to the menu and see newsletter you don't have to sign up for anything to see examples of what these are like I'll provide a couple of different protocols one that is pure static stretching one that involves PNF type stretching and I'll also put down a protocol that involves the antagonistic interleaved muscle training of the sort that I've been describing a few times throughout this episode and then you can try and apply those either separately or maybe combine them in some way that's useful for your goals there are a couple of key elements that are essential for building a safe and effective range of motion increasing program that arrive to us both through the peer reviewed research and admittedly from people that have been involved in teaching and training range of motion for a very long period of time some of you may be familiar with the so-call Anderson method it's been around for a long time actually have never met Anderson I don't I should know this I don't even know if he's still alive I hope he's still alive but in any event there are a lot of different features to the Anderson and other protocols but one of the aspects of the Anderson protocol that I think is highly relevant in fact I know is relevant to the peer-reviewed research that we're going to talk about in a few moments is this notion of pushing through pain and how active or how passive to be about static stretching now this is somewhat subjective right if you think about getting into a stretch again we'll just use the hamstrings for example so you're you're either reaching for your toes while seated or maybe you're using a strap you're uh raising your foot overhead while lying down or maybe um you're you're doing a toe touch type exercise how far should you reach where is the end range of motion should you bounce should you not bounce we're going to talk a little bit more about that in a moment but Anderson has an interesting idea in principle which has thread through a lot of his teachings that I think are very much in keeping with the study that I'm about to describe next where he emphasizes to yes to stretch to the end of the range of motion but not to focus so much on where that range of motion happens to be that day so for instance not thinking oh I can always touch my toes for instance um and therefore that's the starting place for my flexibility training today but rather to take the entirety of your system into account each day and understand that okay provided you're warmed up appropriately that you're now going to stretch your hamstrings for instance and you're going to reach down for your toes but that your range of motion might be adjusted that day by way of tension and stress or by way of ambient temperature in the room and to basically Define the end range of motion as the place where you can feel the stretch in the relevant muscle groups I think this is important because unlike resistance training or cardiovascular training where we can measure distance traveled over time in the case of cardiovascular training or how much weight is on the bar and count repetitions Etc with range of motion training of course range of motion is the feature that we're interested in but there is likely to be a lot of variation from dayto Day based on a number of different internal and external factors and so the erson method is really about getting into static and other forms of stretching I think today we've mainly been focusing on static stretching and holding the end range of motion but really paying attention to the feel of the stretch and the muscles involved and there are parallels in resistance and cardiovascular training too I realize right in the case of trying to build hypertrophy or I should say improve hypertrophy muscle size oftentimes the best advice that one can give is to don't try to lift weights but rather to challenge muscles now of course you need to provide adequate loads in order to get hypertrophy but when you're training purely for strength it's about moving weights when you're training purely for hypertrophy or mainly for hypertrophy it's really about challenging muscles using weights or other forms of resistance and similarly and in keeping with this Anderson method when trying to build limb range of motion doing static stretching at a place where it's difficult but that you can experience the stretch of the muscle cognitively consciously being able to focus on the muscles and their stretch is at least as useful as is evaluating the current range of motion you're able to achieve so what does this mean this means feel the muscles as you stretch them don't just go through the motions and this means don't get so attached to being able to always achieve for instance a stretch of a given distance on a within a given session you might actually find that by just finding the place where you can't get much further and holding the static stretch there that on the second and third set that you happen to be doing that day that your range of motion will be increased considerably maybe not but very likely yes you will and of course evaluating range of motion over time is the key parameter because that's that's the goal of all this type of work now along these lines there is this this variable that we've mentioned a few times of passive versus active stretching and there's this even more nebulous variable this even more kind of subjective thing of how much effort to put into it should you push into the stretch would you even want to bounce a tiny bit would you want to reach into that end point and try and extend it within a given set and session and for that reason I was excited to find this paper um entitled a comparison of two stretching modalities on Lower Lim range of motion measurements in recreational dancers um happens to be done in recreational dancers it's a six- we Intervention Program that compared low intensity stretching which they call Micro stretching they used a capital m so I don't know if that means that it's proprietary although I didn't see evidence of a conflict of interest but they call it micro stretching but to be very clear micro stretching in the case of this manuscript is low intensity stretching and they compared that with moderate intensity static stretch in on an active and passive ranges of motion okay so there are a lot of different variables are here but I'll just highlight a few of the the things that are really most relevant to us and I'll give you the takeaway at the outset and then return to it at the end so that uh if I lose any of yours attention in the next couple of minutes at least you have uh that key takeaway basically what they found was that a six- we training program using very low intensity stretching had a greater positive effect on lower limb range of motion than did moderate intensity static stretching I find that incredibly interesting so very low intensity and we'll Define what that means in a moment here I'm quoting them the most interesting aspect of the study was the greater increase in active range of motion compared to passive range of motion by the micr stretching group so this relates to what we were just talking about a few moments ago as it relates to the Anderson method which is that very low intensity stretching meaning effort that feels not painful and in fact might even feel easy or at least not straining to exceed a given range of motion turns out to not just be as effective but more effective than moderate intensity stretching so what is low intensity static stretching well they Define this as the stretches were completed at an intensity of 30 to 40% where 100% equals the point of pain right so 30 to 40% in these IND indviduals and again I'm paraphrasing induced a relaxed state within the individual and the specific muscle and here they were holding these static stretches I should mention for one minute not 30 seconds now the control group was doing the exact same overall protocol so daily stretching for six weeks the same exercises holding each set for 60 seconds but we're using an intensity of stretch of 80% where again 100 represents the point of pain the point where the person would want to stop stretching I find these data incredibly interesting for I think what ought to be obvious reasons if you're going to embark on a flexibility and stretching training program you don't need to push to the point of pain in fact it seems that even just approaching the point of pain is going to be less effective than operating at this 30 to 40% of intensity prior to reaching that pain threshold the pain threshold being 100% now of course this is pretty subjective but I think all of us should be able to register within ourselves to whether a given range of motion or extending a given range of motion brings us to that threshold of pain or near pain and according to this study at least operating or performing stretching at an intensity that's quite low that's very relaxing turns out to be more beneficial in increasing range of motion than is doing exercises aimed at increasing range of motion at a higher intensity okay so lower intensity stretching I should say lower intensity static stretching appears to be the most beneficial way to approach stretching and I think that's a relief um probably to many of us because it also suggests that the injury risk is going to be lower than if one were pushing into the pain zone so to speak the authors offer a number of different explanations as to why this approach this micr stretching approach might be more effective um here I'm paraphrasing from their discussion where they mentioned that it could be hypothesized that they had improved reciprocal inhibition within the hamstring muscle group so this gets right back to the sorts of neural mechanisms that we talked about before that somehow by doing this low intensity stretching that they were able to access some of those spindle and GTO type mechanisms that we were referring to um earlier and the inhibition of hamstring and quadricep stretches they also offer a number of different um ideas about how this could shift the activation of the so-called sympathetic remember the kind of stress division of our nervous system and to reduce that relative to activation of the parasympathetic arm of the nervous system I confess they have a couple of arguments around sympathetic parasympathetic that are somewhat convoluted I will just In fairness to the Neuroscience on those systems um I wouldn't suggest uh putting too much weight on their arguments about sympathetic and parasympathetic uh to my mind they didn't really uh hold much water but here I'm not trying to be disparaging of the of the overall work which I think is really quite sound which is that low intensity so-called micro stretching is going to be the most effective way to increase limb range of movement over time I want to just briefly return to this idea of whether or not to do ballistic or static stretching before some sort of skill training or weight training or any kind of sport or even cardiovascular exercise like running again the data are really split out there there are even folks who suggest that doing any kind of stretching prior to running is going to lower running efficiency it's going to require essentially more work and more oxygen uptake at a given speed for a variety of reasons and Runners and that Community argue about this endlessly there are papers in both sides in both directions I'm sure I'll hear about some of this in the comments I'm not really going to take a stance on this as a as a consequence because the data are all over the place however I think there's a general logic that we can apply and here I'm borrowing from some conversations and some information put out there by Dr Andy Galpin who I think um is of course both an expert and thinks about these things in a really sound and flexible way no pun intended there are instances for example where an individual might want to do some static stretching to increase limb range of motion prior to doing weight training even if it's going to inhibit that person's ability to lift as much weight why would you want to do that well for instance if somebody has a tightness or a limitation in their neuromuscular connective tissue system someplace in their body and system that prevents them from using proper form that they can overcome by doing some static stretching well that would be a great idea as Dr Galpin points out or for instance if proper stability within the movement requires increasing limb range of motion in some way well then compromising the use of Greater loads uh could be greatly offset by doing some static stretching to improve say hamstr Str flexibility or another muscle group flexibility so we can't always think about just what's going to allow us or inhibit us from using the maximal amount of weight or from running as far as we want to run as fast as we want to run there are instances where people are trying to overcome injuries where they're trying to come back from a reparative surgery or something of that sort coming back from a layoff where some additional static stretching prior to cardiovascular weight training or skill training or sport of some kind is going to be useful because it's going to put us in a position of Greater safety and confidence and performance overall even if it's adjusting down our speed or the total amount of loads that we use so it's you that needs to consider whether or not for you and within a given training session you want to do static training I should say static stretching range of motion training prior to or after that training session and similarly there are a lot of data pointing the fact that doing some dynamic or even ballistic stretching prior to skill training or cardiovascular weight training can be beneficial in part to warm up the relevant neural circuits joints and connective tissue and muscles and as well to perhaps improve range of motion or ability to perform those movements more accurately with more stability and therefore with more confidence and while Dr Andy Galpin would never name any protocol after himself he's far too humble to do that I've named a couple of protocols after him particular the Galpin equation for hydration because he was willing to stick his neck out there and put down some specific numbers that people could follow in order to ensure proper hydration during training you can look up the Galpin equation elsewhere you can just Google it or uh look elsewhere you'll find it and Dr Galpin has also been very thoughtful and generous and I think very accurate in offering a kind of a general organizational Logic for how to think about the goals of par particular training session and thereby to decide whether or not you're going to do ballistic or static stretching and so on and so forth so we can refer to this General approach as Galpin Galpin is that right Galpin Ian logic Ganan logic thus far we've been talking about stretching for sake of increasing lymph flexibility and range of motion but there are other reasons perhaps to embark on a stretching protocol that include both our ability to relax and access deep relaxation quickly as well as even to reduce inflammation and perhaps even combat certain forms of cancer and if that sounds really far-fetched I want to emphasize that the study I'm about to share with you in a moment was actually carried out by one of the directors of a division of the National Institutes of Health and this was the work of Helen Langan who's a medical doctor has done done really important work on the mechanisms underlying things like acupuncture and has approached all that from a very mechanistic Viewpoint right so not looking just at the effects of acupuncture but really trying to understand what sorts of cyto kindes inflammatory uh molecules and pathways are activated what sorts of neural mechanisms get engaged by things like acupuncture that impinges on the fascial tissues and so forth and Dr Lang is a currently a director of the National Institutes of comp compliment Health um and medicine at the National Institutes of Health so this is a major division supported by tax dollars that support systematic mechanistic exploration of things like respiration meditation yoga acupuncture so this is serious science applied to protocols and approaches that have been used for some period of time but really aimed at trying to understand what would the best protocols be to evolve new protocols so there's a really interesting study done in animal models but I think it's a powerful enough result that I think we all should pay attention to it the title of this paper and again the last author is Dr Langan herself is stretching reduces tumor growth in a mouse breast cancer model and yes you can get mice to stretch it turns out that um if you gently lift up mice by their tail and they hold on to their cage there's a there's a way in which you can mechanically stretch them in a way that doesn't harm them first I should mention that Dr Langan and others have shown that just a brief whole body stretch of that sort induces an increase in activation of the parasympathetic arm of the autonomic nervous system again not arm limb arm but the aspect of the autonomic nervous system that creates a whole body whole nervous system shift toward more relaxation so yes indeed stretching induces relaxation at a systemic level not just at a local level and I think that's important probably not surprising to those of you that use stretching regularly but yes it does indeed relax us yes you can do this in mice and see that in mice as well here's what they did for this current study or I should say this was a study published in 2018 in scientific reports they write recent Studies have shown that gentle daily stretching for 10 minutes can reduce local connective tissue inflammation and fibrosis now that's local tissue inflammation and fibrosis as well we now know as systemic inflammation and can induce relaxation systemically in this case they focused on mice not humans and mice were randomized to a stretch versus no stretch condition and were treated for 10 minutes once a day for four weeks so it's 10 minutes of this passive whole body stretching a day for four weeks what's remarkable I mean just I I have to say is just striking is that tumor volume in these mice they were able to induce tumors in these mice and that tumor volume at the end point was 52% smaller in the stretch group compared to the no stretch group this is a highly significant effect and they point out in the absence of any other treatment and they explored whether or not cytotoxic immune responses were activated and um a number of other features they weren't able to get too deeply into the underlying mechanisms but this is pretty remarkable even 3 weeks into this stretching protocol this daily stretching protocol for these mice tumor volume was reduced I mean by you know it's almost haved this is pretty incredible so they have these measures of tumor volume uh and the only difference in the way these animals were were treated and handled was the introduction of this daily stretch I find this result to be of course Limited in the to the extent that it's done in an animal model not in humans we have to point that out but as they point out in their discussion our results demonstrate a 52% reduction in mamory tumor growth over one month in mice undergoing stretching for 10 minutes a day with without any other form of therapy do they think that stretching itself is changing the tumor size No in fact they raised the possibility that stretching because of its impact on the fascia might even create micro environments that are more permissive for tumor growth in certain instances so they're careful to emphasize what I also believe to be the case which is that it's unlikely that the stretching itself was directly acting to reduce tumor size but rather that there's this possible link between inflammation and immune exhaustion mechanisms that if you can periodically relax a nervous system here through stretching that it can affect certain Pathways related to the immune system that would allow the immune system to combat tumor growth to a significant degree so again even though this is a study in mice it argues that relaxation induced by stretching can have a powerful influence on memory tumor growth again a huge effect uh carried out by uh one of the Premier labs and individuals uh who do this sort of work and think about this sort of thing and of course I want to point out it wasn't just Dr Langan that did the study there are a number of co-authors on the study we will provide a link to the co-authors um excuse me we will provide a link to the study so that you can peruse it in more detail if you like now as a related and somewhat final point I'd like to return this to this idea and this place this real estate within our brain that we call the insular cortex the insula as you recall way back at the beginning of this episode we were talking about the Von eono neurons that Constantine Von eono the Austrian scientist discovered and the fact that we are able to make and perform interpretations of our internal landscape pain our dedication to a practice for instance whether or not we are in pain because it's a practice that we are doing intentionally and want to improve ourselves or whether or not it's pain that's arriving through some externally imposed uh demands or situations well the insula is handling all that and fortunately there's a wonderful paper that was published a few years ago now um in the journal cerebral cortex which is a fine Journal this is the year 2014 entitled insular cortex mediates increased pain tolerance in yoga practitioners I'll tell you why I like this study I'm personally not a practitioner of yoga I've taken a few yoga classes over the years I've done some of the hot yoga classes um those rooms can get really really warm I confess um and I've done the kind of standard yoga every now and again it's not something that I've kept up regularly um this study explored uh the effects on brain structure volume in yoga practitioners and for those of you out there that are afficionados in yoga they they pulled subjects from having backgrounds in the v here I'm probably going to mispronounce these different things and for forgive me the Vinyasa yogas the Ashtanga yogas Yer yogas Sanda yogas okay so some people were new to these practices some were um experienced that the important takeaways were that they took these yoga practitioners and they didn't explore their brain structure in the context of yoga itself they looked at things like pain tolerance so they used thermal stimulation basically they put people into conditions where they gave them very hot or very cold stimula and compared those yoga practitioners of varying levels of yoga experience to those that had no experience with yoga so-called controls and they found some really interesting things there a lot of data in this paper but here's something I'd like to highlight the pain tolerance of yoga practitioners was double or more to that of non yoga practitioners even for those that weren't doing the so-called Hot Yoga right they also found that pain tolerance was significantly greater both for heat pain and for cold pain they also found significant increases in insular again the insula this brain region gray matter volume typically when we talk about gray matter we're talking about the so-called cell bodies the uh the location in neurons where the genome is housed and where the kind of all the housekeeping stuff is there and then white matter volume tends to be the axons the wires because they're in sheathed with this stuff that appears white in MRIs and indeed is white Under the microscope and indeed is white it's actually lipid which is myin so increased gray matter volume of the insula is a significant finding um because what it suggests is that people that are doing yoga have an increased volume of these areas of the brain they're associated with interceptive awareness and for being able to make judgments about pain and why one is experiencing pain not just to lean away from pain but to utilize or leverage or even overcome pain so there are many studies of yoga and meditation out there few that have as much mechanistic detail as this one and in fact there's a beautiful figure figure three in this paper that shows that the gray matter volume of this particular brain region scales in a almost linear way with the duration of yoga practice that somebody has been taking on in years so people that had like they had a few subjects that have up to 15 or 16 years of yoga practice had much larger uh left insular gray matter volume bigger brain areas associated with these abilities and I find this interesting because there are a lot of activities out there that don't create these kind of changes in brain volume especially within the insula so it appears that it's not just the performance of the yoga movements but the overcoming or the kind of pushing into the end ranges of motion and to push through discomfort to some extent of course we want people doing that in a in a healthy safe way but that's allows yoga practitioners to build up the structure and function of these brain areas that allow them to cope with pain better than other individuals and to cope with other kinds of interceptive challenges if you will uh not just pain but cold uh not just pain but discomfort of being in a particular position to do that and again we wouldn't want people placing themselves into a compromised position literally that would harm them especially given that earlier we heard that micro stretching of the kind of non-painful sord low intensity sword is actually going to be more effective for increasing end range of motion but this study really emphasizes the extent to which practitioners of yoga don't just learn movements they learn how to control their nervous system in ways that really reshapes their relationship to pain to flexibility and to the kinds of things that the neuromuscular system was designed to do and as a final Point there's a beautiful graph in this paper beautiful I think because it explores some of the more subjective dimensions of yoga and insular function which is a here I'll read it out in the nerdy uh form and then I'll explain what it means this is a frequency histogram of category of mental strategies used by yogis versus controls during the cold pain tolerance task what they're describing here and showing is quantitatively how people are conceptualizing cold pain in order to get through it and the different categories are for instance distraction right some people just choose to distract themselves from pain or to attempt to other people will try to ignore it it's a lot like distraction but nonetheless to engage in negative emotion sort of like like I'm going to dig I'm going to be in resistance to this control subjects tended to use those approaches whereas practitioners of yoga tended to use other sorts of subjective approaches like positive imagery to some extent the ability to relax despite the extreme cold the ability to quote unquote accept like this is just happening despite the extreme cold to observe to third person themselves and the greatest effect of course was to breathe to focus on their respiration as a way to deal with this challenge this cold challenge now all of that is sub are subjective data but I want to remind you that the practitioners of yoga are not just using entirely different mental strategies but they are far more effective at dealing with pain their pain tolerance is much higher as evidenced by the other data in the previous graphs in the paper so while this podcast episode is most certainly not about yoga per se it's about flexibility and stretching flexibility and stretching are elements within yogic practices and of course yogic practices involve breathing and mental work and a lot of other things balance Etc it's a vast landscape as as many of you know but I think that if ever there was a manuscript that pointed to the utility of something like yoga for sake of tapping into a particular set of brain circuits and mechanisms that could Wick out into multiple dimensions of life so day-to-day life stress challenges in dealing with all sorts of external stressors career related family related uh relationally etc etc excuse me but as well for increasing range of motion for increasing flexibility so if ever there was a practice that one could embark on that would not only increase flexibility and limb range of motion but would also allow one to cultiv at some improved mental functioning as it relates to pain tolerance and other features of Stress Management that no doubt Wick out into other areas of life appears that yoga is a quite useful practice and so for those of you that are interested in increasing limb range of motion and you're already a practitioner of yoga great I can imagine that someday there'll be another study like this one and you'll be in that um you know 10 or 15 to 16 year practitioner uh graph you'll be that dot way out on the far end of of the graph that shows that your insula is that much bigger than the rest of ours um and therefore your internal awareness and pain thresholds and Stress Management will be that much better but of course yoga isn't the only way to increase limb range of motion and flexibility up until now we've described a number of different ways to do that and we've arrived at some general themes and protocols again those themes and protocols will be distilled into some specific and precise list in our neural network newsletter but we can revisit a couple of them now just in summary and synthesis static stretching appears to be at least among the more useful forms of stretching so low or zero momentum stretching typically at end range of motion I love this concept of micro stretching uh even though it's just a couple of studies that have addressed whether or not high-intensity or low-intensity static stretch holds are more beneficial the idea and indeed the data that low intensity so 30 to 40% of of what would one would consider painful appears to be more effective than 80% of that threshold I find that incredibly interesting and then there's this idea of frequency it really does appear that getting at least five minutes per week total of stretching for a given muscle group is important for creating meaningful lasting changes in limb range of motion and that is best achieved by 5day a week or six day a week or even 7 day a week protocols but those can be very short protocols limited to do say three sets of 30 maybe even 45 or 60 seconds of static hold although 30 seconds seems to be a key threshold there um that can get you maximum benefit there is no need to do full 60-second holds unless you're doing fewer total sessions per week and of course to always warm up or to arrive at the stretching session warm and then of course there are the other forms of stretching that we touched upon a bit uh things like PNF and we talked about why PNF Works things like the spindle and the gold G tendon organ reflexes that are built into all of us that we arrive in this world with and of course the other forms of stretching that are known to be effective and important such as Dynamic and ballistic stretching again stretching protocols that involve a lot of momentum in order to improve range of motion for performance of particular types of work that one is about to embark on typically that would be physical work but a whole interesting and unexplored Landscape is the extent to which changing limb range of motion and different types of body movement actually shape our cognitive abilities and that will be the topic of a future episode of this podcast if you're learning from and or enjoying this podcast please subscribe to our YouTube channel that's a terrific zeroc cost way to support us in addition please subscribe to our podcast on Spotify and apple and at both Spotify and apple you can leave us up to a five-star review if you have feedback such as comments about the content of this or other episodes or you have suggestions about topics that you'd like us to explore on the 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the hubman Lab podcast we also have a newsletter I've mentioned this a few times during today's episode it is the neural network newsletter you can access that newsletter completely zero of cost by going to Hu lab.com go to the menu and sign up for our newsletter you supply your email we do not share your email with anybody else we have a very clear privacy policy that you can find there if you want to see examples of previous newsletters you can find them there without having to sign up again that neural network newsletter comes out about once a month and we use it to distill out essential protocols from the podcast to synthesize information from the podcast we do believe many people find them useful so sign up for the neural network newsletter if you're interested so thank you once again for joining me today for a discussion about the neural and neuromuscular and connective tissue and skeletal aspects of flexibility and stretching and as always thank you for your interest in science 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