Shoulder Health and Throwing
Take a moment and think of the fastest motions that occur in all of sports. There’s kicking a
soccer ball with full power, taking a slap shot in ice hockey, or even taking a shot in lacrosse. All
of these are no doubt very fast, but they all take a back seat to throwing a baseball. Throwing a
baseball is without a doubt the single fastest motion that occurs in ALL of sports. Elite level
pitchers are able to produce rotational arm speeds of up to 7,000 degrees per second! But do
you know exactly what goes on at your shoulder to produce this type of movement?
Before we dive into the details of what’s occurring at your shoulder during the throwing
motion, let’s review some basic anatomy. There are three bones that make up your shoulder.
Two of these bones, the clavicle and the scapula, make up what’s called your shoulder girdle.
Your shoulder girdle connects your upper limb to the rest of your skeleton via the
sternoclavicular joint (right below your neck). The third bone, your humerus, interacts with your
scapula to form your actual shoulder joint. Here’s a picture to clarify things a little bit.
The picture on the left is your right arm viewed from the front. The picture on the right is your
right arm viewed from behind.
^ The Lovely Bones (any Mark Wahlberg fans reading this? It wasn’t one of his best films, but
Marky Mark is the man and I will not hesitate to use a reference that involves him. Mooooving
on…) Now I’m sure everyone is aware that we have muscles that attach to these bones that
cause all of our movement. In trying not to turn this article into an excerpt from my college
kinesiology text book, I won’t name them all here. But some of the major muscles include the
trapezius, rhomboids, deltoids, pectorals, serratus anterior, latissimus dorsi, and the infamous
rotator cuff. Here’s a visual. (FYI, the rotator cuff is composed of your supraspinatus,
infraspinatus, teres minor, and subscapularis (not pictured))
View from the back.
So what actually happens at your shoulder when you throw a baseball? Well, a lot really. This
isn’t Rookie of the Year where you can just cock back your arm at 90 degrees and throw some
serious heat… quite the contrary. Throwing a baseball requires the coordination and
synchronized motion of all the joints and muscles previously mentioned, and some that
weren’t!
When you move your arm, especially during overhead movements, there needs to be
appropriate movement of the scapula to allow the humerus to move freely. At various stages
during a throw, your scapula may be tilting forward or backward, shifting closer or further away
from your spine, or rotating upward or downward. This might not seem like a big deal, but if
your scapula doesn’t move adequately, there’s a good chance your arm won’t either.
Scapular upward rotation is vital to any overhead athlete. Without proper upward rotation
from your scapula, you likely will not be able to raise your arm overhead without
compensations from other parts of your body (ex: arching your low back, shooting your head
forward). Compensating for this faulty movement pattern can lead to other negative issues in
the future such as improper throwing mechanics, or worse, injury.
During throwing, the arm needs to move throughout a pretty big range of motion at incredible
speeds, especially during acceleration and deceleration. As you can see, there’s overhead
motion occurring which is why appropriate movement patterns at the scapula and humerus are
necessary to complete a throw. In addition to this, there’s internal and external rotation of the
humerus. External rotation occurs during the loading or cocking action of the arm, while
internal rotation occurs during the forward motion or acceleration portion of the throw. For
this reason, the rotator cuff needs to work very hard throughout this entire motion. First, it
needs to stabilize the humeral head within the glenoid fossa (socket). This prevents the
humerus from sliding too far forward or up which can lead to issues such as pain. Second, the
cuff needs to decelerate the internal rotation of the humerus after the ball is released. This is
where injuries to the rotator cuff tend to happen, mainly because the cuff is not strong enough
to handle the load of decelerating this rotation. Ideally we’d like to avoid this, so we want to
make sure the rotator cuff has ample strength. But if a few things go wrong within this motion,
or if compensatory patterns are needed to complete them, injuries can occur. They can be
acute, meaning sudden, or they can be chronic, meaning they have gradually built up over time.
Regardless, they can definitely be avoided with proper training.
One of the most common issues that can arise with regards to shoulder issues is tightness in
the surrounding muscles. For example, if the lats, pecs, or upper traps are tight, it can limit the
movement of the scapula which in turn will limit total arm range of motion. Since these muscles
are used quite a bit during the throwing motions, overworking them in the weight room can
lead to more problems (assuming they’re already tight). Another issue could be weakness of
the scapular stabilizing muscles. If the scapula is unstable, you’re setting yourself up for less
than optimal shoulder movement. Try to remember the phrase “you can’t fire a cannon from a
canoe” when thinking of the shoulder. You can’t expect your arm (cannon) to produce
tremendous amounts of force when your scapula (canoe) can’t maintain stability. Lack of
mobility in the thoracic spine (think middle of your spine, right in between your shoulder
blades) will also limit shoulder mobility as the thoracic spine impacts the positioning of your
ribcage. Conveniently, the ribcage also happens to interact with and affect scapular positioning.
And would you believe me if I told you the positioning of your pelvis affects your shoulder?
So when you have one or a combination of these issues, continually performing overhead work
on the field or weight room might not be the best option for you. Continually utilizing
compensatory movement patterns to achieve full shoulder range of motion is not something
you want your athletes to be doing, as there is a good chance injuries may be a result of this.
Take some time to fix these issues and avoid any unnecessary trips to the physical therapist,
doctor, or disabled list. In a follow up article, I’ll go over some guidelines to follow that ensure
the shoulder stays healthy and functioning efficiently.
Chris Sanchez, CSCS