many of us have probably thought about including stretching into our daily routines as there are many potential benefits to stretching one of the more obvious and common benefits being improved flexibility and range of motion but what is actually happening to our bodies when we stretch and develop adaptations like improved flexibility well part of this answer might actually surprise you as a big part of this resides in your brain and nervous system who would have thought that your brain and nervous system had an influence or any say over your stretching and flexibility so in today's video
we're going to take a look at the brain certain nerves as well as typical muscles that we stretch so that we can figure out what's going on here we'll also talk about some of the most effective types of stretching for these adaptations or the best ways to improve flexibility over time it's going to be a stretchy one if you will filled with some obvious cheesy jokes but let's jump right into this anatomical awesomeness [Music] so when we think about our own flexibility or how flexible we are we often judge or gauge that by how far
we can move a joint through its range of motion or that point in the joint range of motion where we're like that's far enough so let's kind of set the stage with an example here specifically a stretching example with the typical hamstring stretch of bending over and touching your toes and we'll also use some of these plastic bones to help us with this example this is called the oscoxa it forms part of your pelvis and then you can see the femur plugging in there now when I stretch or Bend forward to stretch my hamstrings I'm
going to actually hinge forward at the hip joint this is technically called flexion of the hip if I bring this a little bit closer you can definitely see what that hinging motion looks like now this area that I'm tapping with my thumb is significant because this is where the hamstrings actually attach for you Anatomy nerds it's called the ischial tuberosity a lot of people just call it the sit bone but again let's say we're stretching the hamstring we hinge forward when we get to that point where the hamstrings are like Ah that's far enough and
we're all likely not to be terribly happy with that limited amount of flexibility and range of motion because a lot of us might think we need the hamstring flexibility to be able to say successfully kick somebody in the head if necessary not promoting violence you just never know when you might need to engage ninja mode in self-defense but for whatever reason each side or choose to engage in a stretching routine for a couple of weeks or maybe a couple months and we improve that hamstring flexibility now instead of maybe this being the end point in
that range of motion now because of that increased hamstring flexibility maybe I can go this far and you can see how that could translate to touching your toes easier but also just the overall increased range of motion of a joint now this principle of improving the flexibility of the muscle and that translating to more range of motion of the joint can be applied to the various muscle groups in their Associated joints throughout the body for example if we improve the flexibility of the calf muscles that could translate to improved range of motion at the associated
ankle joint but what is again accounting for these stopping points that feeling of I don't want to go any further as well says the potential changes in improvements and flexibility yes things like the muscles tendons and other connective tissues play a role but as we've strongly implied this amazing structure also plays a big role but how but real quick before I get into the brain and nervous system I want to take a second to say thank you to the sponsor of today's video yoga body Teachers College since we've opened the lab we've had a ton
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in order for us to understand how the brain and spinal cord get involved with stretching and flexibility we first need to see how they communicate with the actual muscles and if we were to zoom into the muscle tissue specifically the meat of the muscle which is known as the muscle belly embedded within the muscle belly we would see these specialized sensory receptors called muscle spindles these little muscle spindles are encapsulated structures that contain these specialized muscle fibers called intrafusal fibers intrafusal just refers to inside the spindle so it's a pretty good name now these intrafusal
fibers inside the capsule are also going to be wrapped with these sensory nerve endings which will then provide information to the brain about the muscle but what type of information is this providing muscle spindles detect and provide information about muscle length so let's use the biceps in this example but again keep in mind this could be applied to nearly any muscle in the human body and again those muscle spindles will be embedded in the belly of the muscle and they're going to detect the length of the muscle and even changes in the length of that
muscle and it might actually be easier to use my biceps first here so for example my biceps is at a certain length right now the muscle spindle sending information into my brain about this length this is a different length new information different length new information different length new information it not only tells my brain the difference between say like this length of the muscle versus that length of the muscle it also tells me this versus this how fast those length changes occur so what does the brain do with this information do we become consciously aware
of it and of course how does this relate to stretching and flexibility well first let's get the signal up to the brain and with any muscle it's going to have to travel up a nerve so in this particular example we have the biceps and there's a nerve here called the musculocutaneous nerve but it would be a different nerve for different muscle groups and those signals from the muscle spindle cells would travel up this nerve and eventually get to the spinal cord then move up the spinal cord and get to the brain once this information is
in the brain it's going to relay to two areas that are important for our discussion one is my personal favorite structure of the brain and that is this which you can see here the cerebellum now besides looking quite amazing it also participates in some amazing functions like smoothing out and coordinating skeletal muscle contractions and it makes sense that it's receiving that information from the muscle spindles about length changes so that it can make the appropriate adjustments to muscle contractions and therefore coordination the other area of the brain that this information is relayed to is an
area called the somatosensory cortex the somatosensory cortex is located in the parietal lobe specifically in this fold or gyrus that I'm probing here all the way up to the midline of the brain now the somatosensory cortex receives all sorts of different somatic senses from the body things like temperature touch pressure pain and of course information from the muscle spindles about those muscle length changes and what this does for you is creates a conscious awareness about body position and even sensation about when you're tugging or pulling on a muscle when you're stretching now this conscious awareness
about body position this understanding of where your limbs are in three-dimensional space and even awareness about trunk or torso position is referred to as proprioception understanding where your body parts are in three-dimensional space and that's why sometimes the muscle spindles are even referred to as proprioceptors they're not the only proprioceptors in the body we can talk about some of the others in a later video but I like to give two examples to help illustrate why proprioception is so important and one of those examples definitely relates to stretching the first example that I kind of want
you to think of is imagine if your eyes the input from your eyes was the only thing that brought you information about where your body parts were in three-dimensional space like yes you can look at your arms see where it is look at your torso and other body parts and your eyes bring that information in but imagine the problems that would arise if that was the only information that you've got about your body position because if we all held out our hand in front of us like this when was the last time you closed your
eyes and this happened where's my arm where is it come back oh you're back now I apologize if I scared anybody with that I do that all the time in class to make sure people are awake and paying attention but that crazy example doesn't really happen right because we would be a hot mess in a dark room or whenever we closed our eyes if we didn't have proprioceptive input coming from the muscle spindles and other sources so next time you turn out the lights or close your eyes to maybe make out with a significant other
be grateful that you have proprioceptive input to be aware of where your body parts are going and also be grateful that the somatosensory cortex can also make sense in process Sensations like tactile stimulation so you can also be aware of someone else's body parts and the second example as to why proprioceptive input is so important and I promise this is finally going to get us to how this all relates to stretching and flexibility but the second example has to do with all of this information that's coming into the brain from the muscle spindles and even
other proprioceptive sources the brain is going to get this information and be able to process it and actually will be able to send signals back to the muscle spindles and the skeletal muscles throughout the body what it can do is adjust the sensitivity of the muscle spindles as well as adjust the tone of the muscles throughout the body so your skeletal muscles are never fully relaxed there's always some level of tone or some level of contraction that's being stimulated by the nervous system and because the brain can take this information and modulate it it can
make some really cool and important adjustments that I just mentioned that'll have to do with stretching and flexibility in just a second but our brain does this all the time our brain and nervous system modulates all sorts of different sensory information and so if I said to you you're probably wearing underwear and or pants if you're not wearing any of those how you consume your online content is your business but I'm assuming most of you are probably wearing underwear and or pants now if I said to you can you feel your underwear and pants up
to this point you probably weren't aware of that sensation but now you can probably feel them around your legs and your nether regions and this is just another example of how your nervous system modulates and prioritizes different sensory input when you're first putting on the underwear and the pants your nervous system is like okay I can feel the sensation do I need to worry about it is it dangerous and when your brain's like okay we're good underwear and pants are safe it'll modulate or kind of de-prioritize or lower the priority of that sensation to the
point where you're kind of not really worrying about it in your conscious thought this also can be applied to the proprioceptive input coming from the muscle spindles when you first change a position your muscle spindles will fire up a little bit and you're aware of the change in position but once you kind of settle into that position as long as it's safe and not compromising you your nervous system again is going to kind of modulate that or put that at a lower priority but if I were to come up to you and grab your arm
and quickly Jerk It In One Direction your muscle spindles would really be fired up by that and they would likely start to protect them by initiating this thing called the stretch reflex and what I mean by protecting them is that this information or the stretch reflex that's coming from the muscle spindles is going to reply protect the skeletal muscles from being stretched too far now I often give my students this textbook definition of the stretch reflex and it's this when a muscle is stretched too far or too fast it's going to contract and the antagonistic
muscle will relax and the classic example of the stretch reflex that many of us have probably experienced occurred likely in the doctor's office when your leg was dangling off the table and the doctor comes up with that little hammer and quickly Taps your patellar tendon some people call it the patellar ligament I prefer patellar tendon because it's just a continuation the quadriceps tendon but we don't need to go down that road so the doctor quickly Taps that patellar tendon that will cause a quick stretch of the Quad muscles and the muscle spindles are like nope
that's too quickly so the signal goes right into the spinal cord now up to this point we've talked a lot about the muscle spindles sending information up to the brain but in the case of the stretch reflex that signal is going to go right into the spinal cord and right back out through a motor neuron to engage the muscle to contract because the opposite of a stretch is a muscle contraction and that will protect the muscle from being stretched too quickly at the same time another motor signal is going to go out of the spinal
cord to the opposing or antagonistic muscle and in this case this is the hamstring because you wouldn't want the hamstring to contract because that would create this tug of war situation and the stretch reflex wouldn't work properly now some sort of a signal will make it to the brain is kind of a little bit delayed or you could think of it as a little bit delayed because we do become aware that the doctor tapped us on that patellar tendon but the stretch reflex the main signal again goes right into the spinal cord and right out
because it does not want to wait for the brain brain's permission in order to protect the muscle so let's apply this information to the example that we used at the beginning of the video of stretching the hamstrings and remember we use these plastic bones to help us with this and as we hinge forward and stretch the hamstring we eventually get to that point where the hamstrings are like that it's far enough we don't want to stretch anymore and we need to acknowledge like we did at the beginning that the nature or the elasticity of the
muscles tendons and surrounding connective tissues do matter and apply to this but as we've seen from this video the nervous system also matters and so when we hinge forward the idea is that as that hamstring is lengthening and lengthening the muscle spindles are sending that information to the brain about those length changes and eventually we get to that point where the brain might say you know that's far enough I don't really trust you to go any further and it sends a signal back to the hamstring to change or increase the tone almost like it's a
slight increase in contraction to stop that stretched hamstring from going any further now now if we were to quickly go into that stretch or almost bounce into it we might actually stimulate that stronger stretch reflex and you might feel a quicker resistance or almost like this pullback that's a little more forceful than you would if you were to go more passively and slowly into that stretch but let's go to this idea again of doing stretching consistently for weeks or months the idea is that the nervous system will adjust and instead of instead of having the
stop stop Point here that stopping point will be later in the range of motion almost as if the brain through that consistent stretching routine is like okay you've been stretching consistently for a few weeks for a few months I'm going to adjust the sensitivity of those muscle spindles and even where in that range of motion I'm going to increase the tone to stop you from stretching you any further so instead of stop having that stop Point here it's almost as if the nervous system allows you to have that stop point a little bit later which
is really fascinating to think about and how you can potentially increase your flexibility and therefore range of motion neurologically and so let's wrap this up with a few housekeeping items one and like many things with the human body we still need more information about how exactly the brain and nervous system can account for improvements in flexibility and even comparing that like we alluded to earlier the changes or potential changes in the soft tissues like the muscles tendons and ligaments how are these interacting together and how much does one versus the other account for improvements in
flexibility it's definitely going to be interesting as we gain more knowledge in this area and the second housekeeping item we need to wrap up with is the type of stretching in the examples we were using in this video we were referring to this static passive stretching where you get to a certain point in the stretch and then hold for an extended period of time there are definitely different types of stretching like Dynamic ballistic PNF to name a few and they definitely have their place but if our goal is to have long-term improvements and flexibility static
stretching tends to be the best supportive for achieving that goal and a routine that tends to work the best would be stretching the muscle groups that you're looking to improve the flexibility in about five to six days a week for 30 to 60 seconds for like two sets you can think of like two sets of 30 seconds so if you're going to stretch your hamstrings you could stretch into that get to the point where you feel the stretch hold for at least 30 seconds and then come back up and rest for a second you could
even stretch an antagonistic or an opposing muscle in between and then go back in for a second time for 30 seconds so again kind of like two sets of 30 seconds for each muscle group five to six days a week and lastly if you've made it this far I appreciate it because we definitely had to go through a bit of information before we actually got to the stretching part but hopefully along the way you'll learn some really cool things about the brain the nervous system and how it interacts with the muscles another thing that I'm
really excited about is I'm about to head to Florida to do a YouTube collaboration with another Creator and one of the things we're going to talk about is yes it's definitely important to have flexibility good range of motion but on the other hand it's also important to train your muscles to be strong in those lengthened positions so it's going to be a lot of fun to come together with this video and I'm excited to show you when I get back but thanks again for watching this video if you're interested in checking out Yoga Body we
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