The three rules of muscles,
you ready? If you remember these
three rules, you can figure out anything. You can figure out what any muscle does
and all you need is a picture. If you can figure out these three rules, our
functional anatomy class is over. That's it. And you can tell me the most
complicated thing a muscle does, you just have to be able to visualize the muscle
and take it through these three steps. Rule number one:
Three rules of muscles: muscles only contract and relax.
They don't twist, they don't bend, they don't shape, they don't tone,
they also don't burn the fat that's laying directly above them. All they do
is contract and relax. They're little machines that shorten and then they relax and
they don't shorten anymore. That's it.
Ready for number two? As you can tell, these you getting terribly
Muscles only work
on joints they cross.
Now, we're taking it up a notch.
My deltoid crosses what joint?
Shoulder so we'd expected to move my shoulder. That makes sense. Would you expect
your deltoid to move your elbow? No, you'd have to have some pretty weird deltoids.
They'd have to attach over here. That's all fine and good and then we start talking
about abs. Does your rectus abdominus cross your hip? Then why does everybody
do this to work their abs? Ever thought about that? It drives me nuts. "I'm working my lower abs." Your
lower abs don't cross your hips either, not that they don't exist or anything,
but they don't cross your hips either. "Well, that still works my abs." Maybe it
does, but are my abs the primary mover of my hip and why did I start moving my hip
to do that? What is the prime mover of my hip? Your psoas. Where's your psoas located?
Goes from spine to hip, which makes sense, it crosses my hip, so it would move it.
Do you know where it's located in relation to here? Just underneath your lower abs.
So people think they're feeling their abs and they're just feeling there psoas
getting jacked up. Great! Now from a more technical perspective, so now I'm just
busting myths and fooling around, which is cool, but biceps we all know the biceps cross what joint?
Elbow and everybody goes, "elbow." Good they cross in front of the elbow, which
means if they cross in front of the elbow they're probably going to pull
my arm which way? This way. This is called elbow flexion but my
biceps also crossed my shoulder.
Muscles will act on joins they cross, so if it crosses my shoulder by connecting
to my coracoid process and my super glenoid tubercle, that's something in my
glenoid fossa. Glenoid fossa- the shoulder cup. So if it crosses in front
of my shoulder this way, what do you think it's going to do to my arm? It's going
to go this way, which is called shoulder flexion.
Not too bad so far. You ready for the third and final rule?
Muscles work best
in the direction of their fibers.
Those are the three rules.
Going over this- muscles work best in the direction of their fibers- we kind of
mentioned it earlier already when we were talking about planes. We said
muscles that are going to take us through the sagittal plane are probably
going to be oriented how? Up and down in the front and back of our body. Muscles
that are going to move us in the transverse plan are probably going to be
oriented how? Across. Parallel with the transverse plane. We could also go obliquely.
That might help us with rotation. That's kind of a mixture of across and up and down. We do have
muscles like that, that's okay. Frontal plane muscles we said are probably
going to be oriented how?
Up and down. Where on our body? On the sides.
So let's take a muscle, let's take a muscle that we all know and
take it through these three rules: the pecs.
All right, we all know where our pecs are right? The pectoralis major,
just going over it real quick. Origins and insertions. You ready?
Sternum, clavicle, costal cartilage and my first seven of ribs, so this area.
Insertion - lateral lip of my bicipital groove, medial lip of my greater tubercle, however you want to say that.
So it's over here. Now my pec only contracts, we're cool with that.
It crosses what joint? Shoulder. So it's going to move shoulder.
Everything we're talking about is going to be joint actions of the shoulder. Good.
That was a huge huge step. That's all we had to do. Now we have to
think about the direction of these fibers and how it's going to pull this
bone. If I start here, like this and my chest shortens, where is it going to
pull my arm?
It's going to pull it out that way? Maybe. Maybe, it's kind of right on top. It might pull
this way. Just pull this way. Put one hand over your pec and then
the other hand, put it right on top of where you would imagine that bicipital groove
to be and then shorten yourself.
There you go. Internal rotation.
Everybody got the three rules of muscles?
I'm kind of a few pages ahead here on the pectoralis major but don't worry
about it. It's still a real good example for what we're doing. We got shoulder
internal rotation. Let's talk about some other stuf. If I put my arm
like this, this hands my pec, now where is it going to pull my arm? This way.
What is this? What is this joint action?
Horizontal adduction. Those are the two biggies. Now we can get a little, you
can get a little more crazy. Can I go back to what we were talking about before?
My clavicular head, this is my glenoid fossa, this is my humerus, some of the
fibers of clavicular head are very up-and-down oriented like this.
With my arm down by my side, what do you think my clavicular head could help
with? It doesn't have a perfect angle for it, but it could help with a little bit.
A little bit of shoulder flexion. Cool. So we could say clavicular head
with shoulder flexion.
Some of the sternal fibers, there's my sternum, come off like this. Pulling at a
downward angle there. What do you think they're going to be able to help with?
It's my favorite example of that joint action ever. How did Hulk Hogan show off his pecs?
You could do cable crossovers or we could just go with the
silliest example ever which is how - yeah the Hulk Hogan. How did he show off
his pecs? You can't go, "Well, I do horizontal adduction." Because then your
hands are in the way. Got to think about this. He showed off his pecs how?
This way right, so you could see his pecs and his arm weren't in the way. Of course,
he had much bigger arms to get in the way than I do but you know what I'm saying.
There's a little bit of adduction that your pecs can do. We could say
that the sternal head
assists, that would probably be the better word, with adduction.
We didn't need a kinesiology book, we didn't need a bunch of crazy research
studies, we didn't need an anatomy and physiology text. We can just figure this
I have people come up to me and they go, "How do you memorize all of that stuff?" "I don't." Really, I don't.
If you get this concept, it doesn't matter what the muscle is. You just kind
of have to be able to determine what the joint is, kind of know how that joint
moves. Today we're going to be dealing with a lot of ball and socket and hinge
joints, the big joints that we deal with as trainers. But as long
as you kind of know how the joint moves you can visualize how that muscle
pulls, all I have to be able to do is name that joint action and I know
everything that this muscle does. You with me? And I can be as creative as
I want to be. I could put the head in any position I want to or the shoulder in
any position I want to or the hip or the knee in any position I want to and it
doesn't matter as long as I can visualize it and go, "Okay,
it crosses that joint, this is how it crosses, when it shortens, it's going to pull the bone and
x-direction. All right I got a good picture of what that looks like,
what joint action is that?