Deltoid Muscles: Video #8 of Introduction to Functional Anatomy

The deltoid muscles are located in the shoulder and part of the upper arm areas of the body. They are responsible for shoulder movement, such as abduction and extension, and also shoulder stabilization. The deltoid is composed of three parts: the anterior, lateral, and posterior deltoid, which all originate from the clavicle and acromion and insert onto the humerus. The deltoid is vital for sports that require aggressive movement of the arm and shoulder,

Transcript

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Alright deltoids, we have three
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deltoids. We have upper, upper how many
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guys have an upper deltoid? Yeah I didn't think so, freak, what are you doing
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with an upper deltoid. All right anterior, one of my big pet peeves middle
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not medial, you don't have a medial deltoid, that's a mistake I see actually
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in text books all the time, medial deltoid yes that makes a lot of sense
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for the most lateral structure on your torso. Alright anterior, middle
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and posterior. These are kind of tricky, your anterior delt goes from, where
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was slim, let me get slim.
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You guys know slim?
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I don't know why you guys buy the real bone skeletons, they are so fragile,
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they're super expensive too. You figure after all the years that people have
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been using skeletons they'd come up with something a little bit more durable. Yeah
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all right this is slim, in case any of you wonder why I started working out to
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begin with this is what I looked like in high school. I had the body of a model
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when I started high school, a female runway, model it was terrible, no joke I
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started 6'1, 145 pounds, my freshman year. Not okay, they tried to duct-tape me
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to a pole and I started lifting weights, that's that's the story of how I became
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a personal trainer. All right so this is slim, your anterior delt goes from this
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right here the edge of your clavicle right, your acromion shelf wraps around
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the front into something called your deltoid tuberosity, deltoid tuberosity
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what's a tuberosity? A bone bump, and this is the bone bump that your deltoid
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connects into. You guys can all find your deltoid tuberosity, just take your hand
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palpate your shoulder right, palpate your deltoid, bring it down to the point right
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here, there's your deltoid tuberosity. Not bad right, there you go. So this one kind
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of goes and wraps around like this, so what joint does it cross?
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Your glenohumeral, your shoulder joint. So all of these are going to be shoulder
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joint actions right. So I'm just going to write shoulder up here, that means
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technically we need a new word bank right, we can't use our scapular
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actions for our shoulder. What's my word bank for my shoulder? So I got abduction
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and adduction,
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I got flexion, I got extension, internal rotation,
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external rotation and horizontal AD and AB duction. So if I'm talking about the
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shoulder it has to be one of those joint actions yes. Alright so let's go back
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to the anterior delt, it's this way. So if it runs in front of my shoulder joint,
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what joint action do you think it's going to contribute to? Flexion, good.
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What if I do this, now where is it? Still in front of my shoulder right, but now
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when it shortens how is it going to pull my arm? Horizontally, you guys got that.
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Yeah so that's horizontal adduction. It also kind of wraps around my humerus too
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right, wraps around just a little bit. Generally things that wrap around bones
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or have an obliquity, obliquity is a diagonal to them, will contribute to some
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sort of rotation. Which type of rotation do you think my anterior delt is going
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to contribute to? Internal.
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What do you guys think? Does that make sense? Touch your anterior
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delt for me, all right now internally rotate, you feel that guy contracting a
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little bit? Yeah. Alright so let's look at the middle delt, the middle delt is
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the part of your deltoid that goes from acromion shelf and runs straight down the
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side the deltoid process. So it runs up and down on the side of my body. What
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plane did we say those muscles would probably work really well for? Up and
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down on the side of my body, frontal plane right. So now we could take our
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word bank and chop it down to just our frontal plane joint actions. Alright
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you guys are 50/50, which joint action is this one going to cause when
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it shortens? Yeah this is abducting away.
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Posterior delt, so my posterior deltoid runs from the lateral aspect of the
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spine of my scapula back down to deltoid process, and so now it runs up and down
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on the back of my shoulder joint, what do you think it's going to contribute to?
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Extension sure. What else, what if I did this, if I did this what is this exercise
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called? A reverse or rear delt fly right, you guys have heard that before. So what
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joint action is that? Horizontal AD or a AB? AB, horizontal abduction, and
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what's this, this one's kind of got the wrap around thing happening right. Yeah so
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since this one's back here though, if it shortens it's going to pull me into...
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external rotation; and if you guys caught on, anterior and posterior delt what's
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interesting about them? They're opposites right, anterior flexion, posterior
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extension, anterior horizontal adduction, posterior horizontal abduction,