-: So the primary elbow flexors,
is actually gonna be the brachialis.
Which it attaches directly to the anterior humorous here.
And it sits underneath the biceps brachi.
This guy attaches right down here at the ulna.
Whereas the biceps fuse together and attach at the radius.
So that's gonna be an important function
we're gonna talk about,
but the brachialis as a whole is the muscle
that adds a tremendous amount of like girth to the arm
and it kind of pushes those biceps out.
So it's kind of what makes them,
it helps to create that peak.
But it is the primary flexor of the elbow,
And that being said,
because it attaches at the ulna and not the radius,
it doesn't have any real impact upon the rotation
with regards to supination/pronation
of that radia ulnar joint.
So we're gonna get that full elbow flexion outta that guy.
And then next to it, we're gonna see the brachioradialis,
which attaches to the lateral humorous here,
and then it crosses this joint,
comes out all the way over here and attaches
into the styloid process, which is thumb side.
And because of its alignment,
that is going to create elbow flexion
in this more neutral plane.
And, but on a functional level
it will also have kind of a moment to be able to
straighten the arm out from pronation,
if it's already in a pronated position.
Or it's going to bring the wrist back
to neutral from a supinated position
just because of the alignment of those fibers here.
So those are your primary elbow flexors.
There are additional muscles that cross
the joint that would be the wrist flexes and extensors,
but we're not really gonna cover those in great detail,
just because they actually lose moment
to continue to elbow flex
after about maybe close to 90 degrees.
The final guy here which,
seems like it would be the most important one,
but does have an alternate function
that we'll talk about in a second.
The biceps brachi has two separate heads,
the short head and the long head on the outside.
And they both fuse together
to a common tendon that attaches into the radius.
The radius is the bone that rotates over the ulna.
So as this guy creates tension,
the biceps can be a massive helper
in creating supination of the lower arm.
But additionally, where these guys attach,
you're gonna see that the short head comes immediately,
attaches to the coracoid process on the scapula itself,
which is a floating joint.
And then you've got the long head that attaches
at the super glenoid tubercle,
that also crosses the head of the humorous here,
attaching right into that scapula.
Now the scapula is one of those things that needs a lot
of stability from the muscular function all around it.
And I would like to say that rather
than the biceps being 100% biased
towards creating a reflection,
it's actually one of those muscles that's going to be
like a force transducer that creates more stability
the more load is being placed on this joint,
creates more stability to create
kind of a cinching effect on the head of the humorous
into the glenoid fossa of the scapula.
So therefore, without this guy here,
this shoulder joint itself
would be tremendously less stable.
So an alternate view of this same elbow flexion function.
When we see the bones exposed here,
we can see the scapula right here.
This right here is your coracoid process.
This little bump where the short head
of the biceps is gonna attach,
and the long head is going to be
at that super glenoid tubercle,
which is actually right above this humeral head
and fits right over this little groove where the bicep,
so the long head of the biceps pass right through,
that's the bicipital groove.
And they come right around just like we see here,
and come down, you've got like we illustrated,
the radius and the ulna.
So the radius rotates right over the ulna.
And both of those biceps fit in,
right into this little notch right here,
which is what creates the ability
for this guy to supinate the forearm.
Then as we were talking about the brachialis,
which sits deep to the biceps,
you've got another insertion point on the ulna itself,
and on the front of the humorous here.
And that guy, because of its insertion point,
is going to merely pull the elbow
into a fully flexed position.
-: So if we look at the application of bicep mechanics
for training or just elbow flexion in general,
Joseph already touched on the fact that
if we're looking at more of a neutral grip position,
that's really gonna start
to involve the brachioradialis here.
We have the brachialis also that is going to be pretty much,
neutral and comparative to the biceps
which are gonna focus on supination.
So depending on what we bias,
we can choose either a neutral grip
or we can go against supination.
So when we think pronation,
in this sense of elbow flexion,
we're almost thinking anti-supination,
like to get away from biceps and to focus
on the other elbow flexors to somewhat disadvantage them,
especially with the intent.
So there's a difference between holding this position
and just kind of like doing this,
which really the biceps are just gonna be
in a lengthened position.
These other things
are gonna have slightly different mechanics,
but having an intent
of maintaining pronation the whole time,
because you're turning in,
because you're creating an intent that's opposite
of the biceps function,
that would be even less than, or even less biceps.
And conversely, if we were to just hold supination
and do a curl there,
okay well that does change the mechanics a little bit
with sufficient load.
All of those elbow flexors are gonna still try
and contribute whatever's possible,
but actually loading and going through the act of supination
or having the intent of trying to maximally supinate,
is going to bias those biceps more.
So there's a difference between just putting yourself
in that position versus trying to achieve a greater degree
of that position or overloading that position
either through like using a offset dumbbell,
or using a rope or a cast handle
that you can put all the leverage
on one side and actually overload
the supination portion of the exercise.
Those things are gonna have a much greater impact
on diversifying which elbow flexors are getting biased.
And the other thing is,
obviously we can look at shoulder positions.
So if we have the biceps here,
because they come up and cross
and attach to the scapula,
as we get to greater and greater shoulder flexion,
they're gonna get shorter and shorter and shorter,
meaning mechanically they're going
to become less favorable to be able to do that work.
So you could actually take Adam to a point
of almost passive insufficiency,
where he could work a neutral grip curl up here,
and essentially really disadvantage his biceps
ability to contribute that work.
You've done this before, right?
And it's this tremendous brachialis
and brachioradialis pumps.
So that's a very good way to be able to
kind isolate those two.
The biceps are really easy by adding
load to supination and eliminating them.
You can use a neutral grip
and add extra shoulder flexion
to disadvantage them that way.
And then just kind of expanding a little bit,
on the biceps ability to kind of help the shoulder joint.
And you have to think of it this way,
if Adam just kind of supports the shoulder joint there
for me for a second,
if I have 10 pounds of pressure in this hand,
and it's pushing that way,
my bicep tendon actually attaches right here.
So it may be producing, you know, a hundred pounds.
So with 10 pounds in my hand and a hundred pounds if here,
that's a hundred pounds of tension through that bicep
that's actually holding the shoulder.
Which is really advantageous
if I'm moving a load further away from my body
like I would be if I was out here.
So it'd be much easier for a weight
that's moving out in my hand to create
a lot of damage to the shoulder joint,
if I wasn't able to keep it really nice
and tightly compressed.
So two things that the bicep is really able to do:
one is it's able to approximate that joint into the fossa
with the help of whatever resistance that we have;
and the other thing is when I'm doing something statically,
it's able to use that with the co-contraction
in the tricep to really kind of fix my arm
in space when there's a load here.
So if you look at a lot of the flexion muscles and stuff,
they have a tremendous amount of isometric,
or these two joint muscles I should say,
they have a tremendous capacity for isometric contractions,
because it's a combination of like fixating the joints
through that kind of compressive force as well.
So that gives them a whole other property
that they can really add to stabilize the joints under load.
When say, we would need to say, fix the elbow position.
So if Adam were doing a fly,
and he was going through this motion
and we're relying on the pecs
to adduct the humorous across the body here,
the load's in his biceps.
So if he's got a load out here,
that load in the bicep is going
to be compressing that joint,
but it's also gonna be really helping fixate this elbow,
without him having to do massive amounts of elbow flexion.
So there's a reason when you're doing flies,
your biceps don't start to get tired.
It's because they have a very efficient line
of pull for fixating this joint,
because it's a very compressive force,
which allows us to use our chest,
our back and all that other stuff,
when we have these two joint muscles
kind of helping us fixate those joints.
It's very important to keep them in there
for a stability perspective.
So if you look at the the exercises
where people will put cuffs up here,
and they will load like flies
or pullovers or something like that.
And they will try and eliminate the elbow from the work,
they're not actually making that healthier for the joint.
And they're not actually gonna end up with more output.
They're actually gonna end up
with less output in the muscles they're trying to train
and actually greater harm to the joint,
because you're taking away the ability
for the biceps and the triceps to reuse that load,
to stabilize the elbow and the shoulder joint.