Knowing the basics of anatomy and how it relates to pitching can make things a lot easier for all of us, especially given the fact that some coaches, including me, are prone to forgetting what players don't know. Given how easy it is to overthink things on the mound though, I want to keep this relatively simple.
So here is a brief overview of some of the things coaches frequently reference and things players could benefit from knowing.
The shoulder is a ball in shallow-socket joint. Think of it like a golf ball sitting on a golf tee. Because of this we need to have really strong external rotators to suck the humeral head onto the socket The joint is also extremely small, and we have very little wiggle room when it comes to keeping the ball on the socket. This means that our scapula needs to be properly positioned on our ribs to give the ball more space to move smoothly.
Glenohumeral Joint - This is the shoulder joint. It is a very shallow, ball in socket joint.
Humeral Head - The bulbous top to your upper arm bone (humerus) that makes up part of the glenohumeral joint.
Scapula - The shoulder blade
Subacromial Space - The space in the front of the shoulder where people will often feel tightness. This is a very small space with many structures, so having a few more millimeters of room in this space can be the difference between a shoulder that feels good and one that feels tight.
Biceps Tendon - This is the tendon that attaches the biceps to the bone. Technically there are two of these, but most of the time in baseball we are referencing the part that attaches up in the front of the shoulder. It feels like a vertical cord in the front of the shoulder.
Middle/Lower Traps - These are the muscles of the back that allow the scapula to upwardly rotate on the ribcage, allowing the arm to move smoothly overhead.
Upper Traps - These are the muscles between the neck and the shoulders. Those who live in the lab, work long hours on the computer, or just sit with a pronounced forward head posture can develop tight, overworked upper traps. Soft tissue work is the answer for these people. For those with severely down sloped shoulders, tightness in this area may be protective. For these folks soft tissue work can be counter productive.
Lats - These are the huge muscles of the back that work to move the arm in many directions, including into internal rotation. Elite throwers use their lats to generate extreme rates of shoulder internal rotation, but it is important to learn to inhibit them as the arm moves into external rotation. It is also vital to balance these scapular downward rotators with the upwardly rotating powers of the middle/lower traps.
Subclavius - This is a small, wormlike muscle that lives just below the collarbone. It can get really junky and make it difficult to get the arm overhead. Check out this video to see how to give it a little love.
Overhead Flexion - When your arms go directly overhead.
External Rotators/External Rotation - The external rotators are the group of muscles that move your arm to an externally rotated position, as in the video. They also work to keep your shoulder packed tightly in the socket.
Teres Minor - A major external rotator that can get extremely tight. It lives just to the backside of the armpit and can be relieved with some light soft tissue work after a tough throwing session.
Internal Rotators/Internal Rotation - The internal rotators are the group of muscles that move your arm to an internally rotated position, as in the video. Often pitchers will be missing internal rotation on their throwing side as an adaptation to pitching.
UCL - (Ulnar Collateral Ligament) - This is the ligament that attaches your upper arm (humerus) to your lower arm (ulna).
Flexor-Pronator Mass - The mass of muscles that serves to flex and supinate your forearm. These muscles support the UCL in its role of keeping the humerus attached to the ulna.
Supinated - Think of this as holding your hand as if you were holding a bowl of soup from the bottom.
Pronated - Think of this as holding your hand as if you were palming a bowl of soup as you would a basketball, which is the way a pro soup holder would hold it.
External Rotators/External Rotation - The external rotators are the group of muscles that open your hip, as in the video.
Internal Rotation/Internal Rotation - The internal rotators are the group of muscles that close your hip, as in the video.
Extension - When you move your leg behind the line of your body. Think of your back leg at ball release. Or just watch this 2 second video.
Flexion - When your leg comes towards your body. Think of max leg lift. Or just watch this 1 second video.
Thoracic Spine - This is the middle to upper part of the back.
Thoracic Rotation is when we rotate through this part of the back.
Thoracic Extension is when we arch through this part of the back.
Thoracic Flexion is when we round through this part of the back.
Lumbar Spine - This is lower part of the spine. We want this part of the spine to be pretty stable.
Cervical Spine - This is the upper part of our spine, better known as the neck. We want to avoid a forward head posture. Instead, we want to remain neutral.
Anterior - The front
Posterior - The back
Medial - The inside/the middle
Lateral - The outside/away from the middle
Superior - The top/above
Inferior - The bottom/below
Hopefully that wasn’t too much to digest at one time, but if it was, hopefully it was comprehensive enough to come back to now and again when something you see on a program or something a coach says seems confusing.
But more importantly, if you’re confused when a coach says something, that’s on them. But it’s on you to tell them that you don’t understand. Otherwise they'll think you've communicated when you haven’t. If we all take ownership of being on the same page, everybody wins.