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  • ANNOUNCER: Thanks to Curiosity Stream for supporting

  • PBS Digital Studios.

  • So stay like this, and then lift up like this.

  • Use this momentum to kick your legs up even if you

  • don't go all the way yet.

  • And like bend your legs, and see if you can go

  • to just the top of your head.

  • Just kidding.

  • Hey.

  • I'm Diana.

  • You're watching "Physics Girl."

  • And last week, I got to hang out with contortionist

  • and YouTuber, Sophie Dossi.

  • We did some science experiments for her channel.

  • And while we were hanging out, I realized that, as a physicist,

  • I know absolutely nothing about what

  • stretching does to your body and whether there

  • is a scientifically-supported way of becoming more flexible.

  • There is.

  • Stay tuned.

  • I didn't know, so I headed over to USC

  • to meet with a bio mechanist to find out the latest science.

  • I'm Michael Rowley.

  • I am a PhD candidate in the division

  • of biokinesiology and physical therapy.

  • My first question was, is there something

  • different about Sophie?

  • I'm just going to get into a back bend,

  • and like lift up my feet.

  • Oh my gosh.

  • Yes, yes.

  • Very different.

  • But I mean, like biomechanically,

  • does she have a superpower?

  • There's evidence that people who are hyper flexible--

  • Quick pause.

  • Hyper flexible or hypermobile is actually a scientific term.

  • And there is a test used to determine whether someone

  • is hyper flexible.

  • It's called the Beighton score, and I'll

  • link to it in the description if you want to test yourself.

  • OK.

  • So people who are hypermobile--

  • Those people have a little bit more relatively

  • of the more stretchy collagen than the type I collagen.

  • Uh-huh.

  • I need a quick refresher on collagen. Take it away Michael.

  • So a bone to bone connection is a ligament.

  • And then a muscle to bone connection is the tendon.

  • Tendons and ligaments are made up

  • of mostly collagen, which is a type of protein.

  • And there's different types of collagen.

  • So tendons and ligaments have primarily type I collagen,

  • which is a really strong type, and then also some type III

  • collagen, which will be more stretchy,

  • and then may also include some elastin, which

  • is another type of connective tissue

  • that's very elastic and stretchy.

  • So the ratios of those things can be different.

  • Got it.

  • So Sophie might actually have a different material makeup

  • of the tissues in her body, like she

  • might have more of that type III collagen, which

  • would allow her to do things that the average person can't

  • do.

  • Fact was, I almost can't overstretch anymore because I'm

  • just completely in half.

  • So it's like I have pushed the limit on that,

  • like there's just--

  • I mean you can't-- you're not a ghost.

  • You're not a ghost.

  • But how flexible is Sophie?

  • Yeah.

  • Before I started contortion, I was always

  • more flexible than that average gymnast.

  • Oh, than even the average gymnast.

  • Yes.

  • Not even the average person.

  • Yeah.

  • When I was little, I use to watch TV

  • with my feet over my head.

  • Yeah.

  • That's flexible.

  • OK.

  • But how do you get flexible biomechanically?

  • I guess my first question is, when you stretch,

  • what parts of your body are stretching out?

  • Yeah.

  • So when you stretch, you're going to increase flexibility

  • and excursion in all those tissues-- muscles, tendons,

  • ligaments.

  • The most short-term, the fastest, most acute effects

  • will be in the muscle.

  • So your tendons and your ligaments

  • are stretching out too?

  • How does that work?

  • They seem so sturdy.

  • This is getting to the heart of what I really, really want

  • to know, which is, what is physically happening

  • to all of these tissues?

  • The actual pieces of physiology

  • that change with stretching, the body will change the water

  • content in the material.

  • That's probably the fastest way.

  • And then you can also induce some

  • stem cells that still live in the tendon material themselves.

  • And those can differentiate into more cells.

  • They can produce more or slightly different

  • types of febrile or proteins like that collagen

  • that I talked about.

  • Humph.

  • So your body can change the material properties

  • of your tissues by stretching?

  • Cool.

  • Another way is that you actually modify sensation.

  • So you might experience some mild pain the first time

  • you're going to stretch, but you'll actually

  • desensitize yourself to that pain over repeated

  • stretching multiple days a week for multiple weeks.

  • Hold up.

  • Really?

  • Yeah.

  • One way of getting more flexible

  • is just becoming more numb to pain?

  • It actually really feels good.

  • It feels like a nice, good stretch.

  • It doesn't feel like a hurt stretch at all.

  • Crazy.

  • I have no chance.

  • Another change that happens physiologically with

  • stretching, our muscles have an alpha-gamma reflex loop.

  • So when you stretch your muscle, there's

  • this automatic signal that gets sent to the spinal cord.

  • It doesn't even go up to the brain and back.

  • The spinal cord then tells the muscle to contract.

  • That coactivation would be bad for stretching, right?

  • If you're stretching the muscle, and then the muscle's

  • trying to pull back on you.

  • So over time, you can actually down regulate that reflex loop,

  • and that's been shown to happen when you stretch

  • for long periods of time.

  • Lastly, you actually add length to the muscle fibers.

  • And you do that by adding sarcomeres,

  • which are sort of the contractile unit

  • producing the active contraction of muscles.

  • Wow.

  • Bodies are so complicated.

  • So let's recap.

  • Stretching can change the water content in your muscles,

  • stem cell differentiation, how much you feel pain,

  • that alpha-gamma reflex loop from your muscles

  • to your spinal cord, and the length of your muscle fibers.

  • That's cool.

  • Now I know what's going on when you get more flexible.

  • Biomechanics is cool, almost as awesome as physics--

  • maybe more useful though-- which brings me to my last question.

  • What does science have to say about how to get more flexible?

  • Well, Michael pointed me to this really interesting

  • meta-analysis, which is like a big study that actually

  • synthesizes all the findings from other studies,

  • in this case, 23 other studies, which

  • looked at how to get the best benefits on improved range

  • of motion, or flexibility.

  • And they found that static stretching,

  • that is when you ease into a stretch

  • and then hold it for 30 to 60 seconds, that's

  • the best for improved range of motion, or flexibility.

  • And as far as how much to stretch,

  • they found that five minutes total

  • per week of one muscle group was sort of the lower limit.

  • But you didn't see much more of a benefit over 10 minutes

  • a week of stretching.

  • And six days out of the week was the plateau of seeing returns.

  • So the more you stretch per day doesn't

  • keep increasing the benefits, but that frequency,

  • six days a week and then the five minutes

  • total for that week, is what's important.

  • So commence operation stretching muscle group

  • for six days a week, five minutes total.

  • Now, of course, different types of stretching

  • have different benefits, so I will

  • link to some of the other literature in the description.

  • But more importantly in the description

  • is the video that I did over with Sophie on her channel.

  • I channeled my inner YouTuber, and we did a challenge

  • where all the science experiments I was doing,

  • Sophie had to do with her feet.

  • She's insane.

  • It was amazing.

  • I had so much fun filming with her, so check out that video

  • and subscribe to Sophie's channel.

  • And thank you to Michael at USC who blew

  • my mind with biomechanic facts.

  • Physicists don't get to learn a whole lot of biomechanics.

  • And that's it.

  • Subscribe to Physics Girl if you want

  • to learn more stuff with me that I'm

  • randomly interested in every couple of weeks.

  • Thank you so much for watching and happy physicsing.

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  • I would recommend watching "Dream the Future",

  • which is a new 19-part series about what the future's going

  • to be like, what's it going to be like when we do sports,

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B1 US stretching collagen flexible muscle sophie stretch

What stretching actually does to your body ft. Sofie Dossi

  • 181 13
    大文 posted on 2022/07/18
Video vocabulary

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sort

US /sɔrt/

UK /sɔ:t/

  • verb
  • To arrange things in a systematic way, typically into groups.
  • To arrange things in groups according to type.
  • To organize things by putting them into groups
  • To deal with things in an organized way
  • noun
  • A category of things or people with a common feature; a type.
  • Group or class of similar things or people
content

US /ˈkɑnˌtɛnt/

UK /'kɒntent/

  • adjective
  • Willing to accept something; satisfied.
  • Being happy or satisfied
  • In a state of peaceful happiness.
  • In a state of peaceful happiness.
  • other
  • To be satisfied or willing to do something.
  • other
  • To make (someone) happy and satisfied.
  • To make (someone) happy and satisfied.
  • To satisfy (someone).
  • To make (someone) happy and satisfied.
  • other
  • Information made available by a website or other electronic medium.
  • Information made available by a website or other electronic medium.
  • The things that are to be found inside something.
  • The things that are to be found inside something.
  • The subject matter of a book, speech, etc.
  • other
  • Information or other material put out by an individual or organization via communications mediums.
  • The amount of a particular substance contained in something.
  • A state of peaceful happiness and satisfaction.
  • The things that are to be found inside something; the ideas, facts, or images that are contained in a book, article, speech, etc.
  • noun
  • Information in something, e.g. book or computer
insane

US /ɪnˈsen/

UK /ɪnˈseɪn/

  • adjective
  • Extremely foolish or unreasonable.
  • In a state of mental illness; mad.
  • Mentally ill; crazy
  • Being crazy or stupid
material

US /məˈtɪriəl/

UK /məˈtɪəriəl/

  • noun
  • Cloth; fabric
  • Supplies or data needed to do a certain thing
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  • Supplies needed for a task or activity.
  • other
  • Fabric or cloth.
  • Information or data used for a particular purpose.
  • A substance from which something is made or can be made.
  • adjective
  • Relevant; (of evidence) important or significant
  • Belonging to the world of physical things
  • Relating to physical matter or substance.
multiple

US /ˈmʌltəpəl/

UK /ˈmʌltɪpl/

  • adjective
  • Having or involving more than one of something
  • Capable of handling more than one task or user at a time.
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  • More than one; many.
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  • noun
  • Number produced by multiplying a smaller number
  • A ratio used to estimate the total value of a company.
  • A number of identical circuit elements connected in parallel or series.
  • A number that can be divided by another number without a remainder.
  • pronoun
  • More than one; several.
stretch

US /strɛtʃ/

UK /stretʃ/

  • noun
  • Making arm, leg muscles longer to ease them
  • A consecutive row of things
  • A period of time
  • verb
  • To make your arm, leg muscles long to ease them
  • To make something bigger by pulling on it
term

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UK /tɜ:m/

  • noun
  • A condition under which an agreement is made.
  • Conditions applying to an agreement, contract
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  • The normal period of gestation.
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  • Fixed period of weeks for learning at school
  • The (precise) name given to something
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  • other
  • Give a specified name or description to.
  • verb
  • To call; give a name to
description

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UK /dɪˈskrɪpʃn/

  • noun
  • Explanation of what something is like, looks like
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  • A summary of the qualities and features of a product or service
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improve

US /ɪmˈpruv/

UK /ɪm'pru:v/

  • verb
  • To make, or become, something better
  • other
  • To become better than before; to advance in excellence.
  • To become better
  • other
  • To make something better; to enhance in value or quality.
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average

US /ˈævərɪdʒ, ˈævrɪdʒ/

UK /'ævərɪdʒ/

  • noun
  • Total of numbers divided by the number of items
  • verb
  • To add numbers then divide by the number of items
  • adjective
  • Typical or normal; usual; ordinary