EVERYTHING You NEED to Know BEFORE Working Shoulders! (Part 1)

What's up guys, Michael Kamalo here aka Dr. Gaines and in this video I'm going to go over everything you need to know about shoulder anatomy and physiology in order to maximize the effectiveness of your workouts. Now since there's a lot of material to cover here and I want to do it all justice, I'm actually going to split this up into two videos. In the first video, part one, I'm going to go over the shoulder joint as a whole, including all of the muscles that go into its movement. Hint, there's a lot more than just the deltoids. And then in part two, I'll go over the deltoids specifically and a deep dive into the three different heads of the deltoids and how you can work out each one of them. So first we need to understand a little bit about the joint itself. The shoulder is actually called the glenohumeral joint. I call that because the humerus comes into contact with the glenoid fossa, which is that concave shaped edge of the scapula. So think of it as my fist is the head of the humerus and my hand is the glenoid fossa. And so the shoulder moves around inside that joint. The glenohumeral joint is the most complex joint in the human body. It also allows for more mobility than any other joint. But in anatomy, mobility comes at a price and that is stability. In other words, the more movement a joint has, the greater chances are that something's going to go wrong. And that's part of the reason why the shoulder is the most commonly injured joint for weightlifters and athletes. There's another big reason for that, and I go in detail over it in another video that I will link below. Right now, what we're going to focus on is understanding all of the muscles in the shoulder. And there are 17, 17 different muscles that cross the glenohumeral joint. And therefore when activated, move your shoulder to one degree or another. Now, some of you may be thinking that I don't care about all the other muscles. I just want to work my deltoids. However, if you really want to hit your deltoids and maximize the efficiency of your deltoid workouts, it is imperative to understand the other muscles that move the shoulder for multiple reasons. But a big one is that if you know what other movements the muscles do, then you can isolate them and keep them from contributing to lifting the weight when you're working your deltoids. So you can isolate it much better and put a lot more load on the deltoids themselves. For example, there are many lifts that people do where they think they're working their deltoids, but in reality, they're really activating mostly their trapezius or pec major or the coracobrachialis. And obviously in those situations, you're going to be leaving results on the table. You're not going to get the same workout on your deltoids that you've otherwise could. So now we're going to go over those 17 muscles one by one, and I'm going to break it down by movement. So we will start with what muscles do flexion of the shoulder. Flexion is moving your arm out and up in front of you. And remember, as we go over these muscles, we're excluding the deltoids for now. Just forget about them. I'm only going to be talking about the other muscles that do those movements. Muscle number one that flexes the shoulder is the coracobrachialis. It is a relatively small but powerful muscle that originates here on this bony process of the scapula called the coracoid process and inserts down here on the front of the humerus. Now, I know it's probably hard to see that, and so that's why I've also included the images on my left here so that you can see those in better detail. And as a quick side note, you'll see me talk a lot about origination points and insertion points. Why are those so important to understand? Well, in order to know what any muscle does, and therefore how to most efficiently work out that muscle, you have to know where it originates from and where it inserts, because that will tell you what that muscle does. For example, because the coracobrachialis originates here on the scapula and inserts on the front of the humerus, what's it going to do when it contracts? Well, it's going to bring that up closer to the origination point. The insertion point will become closer to the origination point, and in this case, it flexes the upper arm up. There are two more muscles that do flexion of the shoulder, and the second is the biceps. Now, most people understand that the biceps flexes the arm at the elbow, but most do not know that it also flexes the arm at the shoulder, and the reason is because of, again, those origination and insertion points. The word biceps has bi in it because it has two parts. As you can see, they both have the same insertion point just past the elbow on what's called the radial tuberosity, but as you can see, they have very different origination points. So right now, we're focused on the long head of the biceps, which is the most lateral one, curls up around the head of the humerus and originates from a point on the scapula called the supraglenoid tubercle, supra meaning on top of the glenoid, and tubercle just refers to ridges on the bones that stand out. So when the long head of the biceps contracts, not only will it pull up on the radius bending the elbow, but it will also pull from its origination point up here on the scapula and flex the arm at the shoulder. As another side note of why it's so important to understand anatomy, it actually means that you don't get a full contraction on your biceps unless your arm is flexed up at the shoulder. The third muscle that flexes the shoulder is the pectoralis major. Now, as you can see, it inserts on what's called the greater tubercle of the humerus, aka big bony part on the arm. However, there's not just one origination point. The pec major is so large that it has multiple different origination points and therefore has multiple different actions. Because of that, the pec major is broken up into three different functional parts, the clavicular part, the sternal part, and the costal part. So which part of the pec is going to flex the shoulder? Well, that means the fibers have to be pulling the humerus up, so it is the clavicular fibers of pec major and called clavicular because they originate from the clavicle or the collarbone, and then they insert there like all of them do on the humerus, and so when those contract, it's going to pull your upper arm up and flex the shoulder. Activation of those sternal fibers is going to adduct your arm or bring it closer to your body, and it's also going to immediately rotate your arm. And as you can see, since the costal fibers are below the insertion point, they're going to pull down on the shoulder. That's actually why decline presses work your lower chest. I'll link another video below where I actually go over pec major in a lot more detail and the 10 ways to work it. So that covers flexion of the shoulder, and now we're going to move into abduction, which is moving your upper arm away from your body to the side. That brings us to muscle number four, and that is the supraspinatus. The supraspinatus originates on what's called the supraspinous fossa of the scapula. Fossa generally means a hole or valley type of landmark, and so again, I know this may be hard to see, but the top of your scapula all along that border there is where it originates from, and then it will go under this top part of the scapula, which is called the acromion, and insert on the head of the humerus, specifically the greater tubercle of the humerus, aka the big bony part. So what's going to happen when the supraspinatus is activated and those fibers contract? Well, it's going to pull on the head of the humerus and abduct the arm. So what's really important to understand here is there are multiple studies that show that the supraspinatus is exclusively the muscle in charge of the first 15 to 20 degrees of abduction. So the deltoid does not even get activated until after your arm is about here, and I'll go into that more detail in part two of this video. The next muscle that abducts the arm at the shoulder is one that you probably wouldn't have guessed, but it is the serratus anterior. It's that finger muscle that lies along your ribs here, specifically ribs 1 through 9 are where it originates from, and then it travels under the scapula and inserts on the backside of the medial border of the scapula. So what's going to happen when it contracts? Well, it's going to pull the scapula closer to your body, and that inevitably ends up abducting your arm. The last muscle we'll go over that does abduction of the shoulder is actually the short head of the biceps, but that's only true if your arm is rotated backwards and to your side. As we already went over, both of the biceps insert down here on the radial tuberosity, but the short head originates from this coracoid process, and so if your arm is rotated out, then it is one of the primary muscles that will be activated in order to pull the humerus closer to the scapula and abduct the arm. It also does give some activation with flexion of the shoulder, but is a minor player there. However, again, when rotated out, it becomes a major player in abduction, and that's a great example of how very small variations in movements, positions, resistance angles of your body can have a drastic impact on how much each muscle gets activated, how much you're working. Next, we will go over extension of the shoulder. If flexion is moving the arm out and up, then extension, which is the opposite, is moving your arm back and even hyper-extending your arm, which is bringing it behind your back. The first extensor we'll discuss is the latissimus dorsi, most commonly called the lat. It originates from the spine, specifically T7 to T12 of your vertebrae, and travels up to insert on the lesser tubercle of the humerus, or the smaller bony point, and so when the shoulder is in a flexed position, it's stretching the lats, and then it is the lats along with a couple other muscles that will pull it back down or extend the arm at the shoulder, and it also does some hyper-extension of the shoulder, but it's not a major player. What is a major player in hyper-extension is the next muscle, and that is the teres major. The teres major originates on the inferior angle of the scapula, the bottom, and then inserts similarly on the back of the humerus, specifically the lesser tubercle of the humerus, the smaller knob. So just like the lats, when the shoulder is flexed, it extends it and is a major player in hyper-extension of the shoulder. The other player in extension and hyper-extension of the shoulder, you may not have guessed, but it is the triceps. The long head of the triceps, specifically, is the only of the three heads that does not originate on the humerus. The other two originate on the humerus and insert down here on this bony part of the ulna called the olecranon, and so when activated, extend the elbow joint. However, the long head of the triceps originates up here on the scapula, specifically the infraglenoid tubercle of the scapula. Infra below, below the glenoid tubercle, little knob. So what's going to happen when the long head of the triceps is activated? Well, it's going to pull the ulna closer to the infraglenoid tubercle of the scapula. Another example of the importance of anatomy. That means that you do not get a full contraction of the triceps, the long head of the triceps at least, unless the arm is bent in a hyper-extended position, and I do another video on that, which again, I will link below. That brings us to our next motion, which is elevation of the shoulder, or bringing your shoulder up. There are two primary muscles involved in elevation of the shoulder. The first is the trapezius. Trapezius is one of the largest muscles in your body and expands virtually the entire back, and similarly to pec major, is due to that, it's broken up into three different functional parts. The descending head, the transverse head, and the ascending head of the trapezius. So what part is going to elevate the shoulder? Well, the ones that are above the shoulder. So the descending part of the trapezius originates from the back of the skull, as well as some of the cervical vertebrae, and then travel down and insert all along the spine of the scapula, which is this bony part sticking out on the back of your shoulder. So when those contract, it's going to bring the spine of the shoulder closer to the head. Now that's important to understand because when people say they're going to do shoulder shrugs, well, they're actually not working their deltoids at all. There's trapezius and one other muscle that is primarily responsible for that. The other muscle is the levator scapula. You can guess what it does just by the name, leve, elevate, scapula. So it originates from the C1 and C2 cervical vertebrae, specifically the transverse processes, which are the ends that stick out to the sides, and inserts on the acromion, which is the lateral most part of your scapula. Most people can feel it in their shoulder. So again, when it contracts, it pulls the shoulder closer to the bottom of your head. The next motion is retraction. Retraction, bringing your shoulder back behind your body. I won't take a whole lot of time on this one because it's the muscles of the back that are responsible, and most people aren't trying to work their shoulder when they do back workouts. However, for sake of completion, there's the rhomboids, rhomboid major and rhomboid minor, which originate along the spine and insert mostly along the medial border of the scapula, therefore bringing your shoulder back behind your body. And then there is the acromial section of the trapezius that we went over earlier. The next movement is protraction of your shoulder, which is the opposite of retraction. Retraction, protraction, and protraction is a very common movement in people working their shoulders. There are two primary muscles responsible for protraction. The first is the serratus anterior, which we already went over because it originates from the front of the ribs and then inserts back behind the scapula along the medial border. It's going to pull that shoulder girdle tight against the body. The other muscle that protracts the shoulder is actually pectoralis minor, which originates on the medial ends of the ribs, specifically ribs three through five. But unlike pec major, it does not insert on the humerus. Pec minor actually inserts on the coracoid process. Now we've gone over a few muscles that insert there now, but you can see how when it brings the insertion point closer to the origination point, it's going to protract your shoulder. And there's another movement it does, and because it's pulling from beneath the coracoid process, it also depresses the shoulder, brings it down. The final two motions we're going to hit are internal and external rotation of the shoulder. A lot of people think that when they grab a cable or worse, a free weight and do internal and external rotation, that they're working their deltoids. In reality, there's very minimal activation of the deltoids. We'll start with external rotation, and that brings us to the infraspinatus, infraspinatus spine. So the infraspinatus is right below the spine of the scapula and originates from what's called the infraspinous faucet, the valley landmark that lies below the spine, and then comes across and inserts on the greater tubercle of the humerus. So you can see that when it's activated, it's going to pull this greater tubercle of the humerus, which is right now facing laterally, and it's going to twist it. Now, the bones here can't really do that movement, but it's going to externally rotate the shoulder. The other muscle that externally rotates the shoulder is the teres minor. We already went over the teres major, but the minor originates along the lateral border of the scapula and then also inserts on that greater tubercle of the humerus. Again, when that contracts, it's going to externally rotate the shoulder. The antagonist for these two muscles and the muscle that does internal rotation of the is a muscle called the subscapularis. Sub being under or behind scapula, it actually originates from the backside or underside of the scapula and then travels around to insert on the front of the humerus in what's called the lesser tubercle or the smaller knob. And so when that contracts, it's going to bring that front of the humerus closer to the backside of your scapula. And the result is internally rotating your arm. Now, if you remember, I did mention one other muscle that also does medial rotation of the shoulder, and that is pec major. So if you have a cable and you're doing internal rotation, you're not touching the deltoid at all, but it actually can be a pretty great finisher or superset for working your chest. And there you have it. Those are the 17 muscles besides the deltoid that move the shoulder joint. As you can see, I wasn't kidding when I said it's the most complex joint in the body and really just brushed the surface. But that's why when a client tells me they want to work their shoulders, I'll ask them to be a little more specific. It also emphasizes how important it is for anyone who wants to get serious about weightlifting or fitness to understand the anatomy of their body before they go around throwing weights. Because again, very slight variations in position, motion, resistance angle can have drastic impacts on how much you are working each muscle and not to mention can have a dramatic impact on preventing or rehabbing injuries. So now that we understand the shoulder as a whole, we're ready to go into more detail on the muscles that most people are referring to when they say they want to work their shoulders, and that's the deltoids. So stay tuned for part two. I'll be releasing that within the next few days. If you like these videos, make sure to subscribe and turn on those notifications, and we'll see you then.