By: Dr. Trey Martin PT, DPT
If you are or have ever been a baseball player, you know that throwing a baseball can flat out hurt. One key thing that most baseball players don't know, is your shoulder motion can influence how likely you are to get injured.
One important range of motion that I look for when assessing baseball players, is the internal+external rotation arc. Check out the video below for my full breakdown.
We want IR+ER to be roughly equivalent between the throwing arm side and the non-throwing arm side. Baseball players will have more external rotation on the throwing side than on the non-throwing side and from this adaptation they will also have less IR on the throwing side. This is NORMAL. Throwing causes bony adaptations in the humerus that causes the throwing arm to sit in a slightly retroverted position by about 10 degrees.
Key Points:
1) External rotation will be greater on the throwing arm side and internal rotation will be less. That is normal. We don't want to correct the throwing arm internal rotation to match the non-throwing side.
2) We want the total arc (external rotation+internal rotation) to be equivalent. If the arc on the throwing arm is 200 degrees of motion (140 ER 60 IR) and the non-throwing arm is 180 degrees of motion (100 ER 80 IR), we might consider the throwing arm as having too much motion and this person may benefit from a strengthening program. Conversely, if a throwing arm has 160 degrees of motion (120 ER 40 IR) and the non-throwing arm has 180 (100 ER 80 IR), we may need to investigate why the throwing arm has range of motion restrictions and try to increase range of motion. This is not absolute and is person dependent, but I just wanted to share how we can use the total arc in our assessment and treatment plan.
3) It is important to maintain external rotation range of motion and shoulder flexion range of motion over the course of the season. This lessens injury risks to the elbow. Pitchers can lose range of motion over the season and get tight. We can address this with soft tissue treatment, joint mobilizations, and a good arm care exercise program.
If not all of this makes sense, that's okay! Reach out to me on here, or send me a message on Instagram @athletedocrehab
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