If you take the time to measure the external rotation on your pitchers prior to training you can learn a lot about how to train them.
I have seen pitchers that have anywhere from 95 degrees to 140 degrees of external rotation. Now while this is a passive measure it is still important to note. What I have noticed is even if I have a guy with 110 degrees of external rotation he may still get to 160 degrees of shoulder rotation when pitching with the Motus sleeve.
According to Seroyer, MD & Nho, MD “Increased amounts of shoulder external rotation help to allow the accelerating forces to act over the longest distance,25 allowing greater pre-stretch and elastic energy transfer to the ball during acceleration.21,31,35” While greater amount of external rotation can be a predictor of increase velocity it also causes increased stress on the UCL and we all know what that means.
The key to having external rotation be a predictor of pitching velocity is how is the motor control or strength during the extreme range. Just because I passively measure someone at 140 degrees of external rotation does not mean they can control that full range of motion. In fact most athletes that have extreme ranges of motion more than likely lack the strength necessary to use the full range of motion and will become injured.
For example, one of my athletes with a range of 140 only can display motor control and strength at 110. He can get to 140 but only control 110 before he would try to use his upper trapezius or could not provide proper resistance past 110 degrees of range of motion.
One of the popular trends is weighted ball work to increase velocity. While doing, the work is a simple form of over-weighted (strength) and under-weighted strength (over-speed) work. I do believe you can gain some velocity from a properly administered weighted ball program but most of the work is helping you gain external rotation.
I won’t go into much more detail on the weighted ball work other than I do believe if it is properly administered athletes can see an increased velocity. By properly administered I mean the proper volume and intensity that is determined on the athletes age and training age. I would also suggest that they have been through a training and shoulder strengthening program prior to starting a weighted ball program.
Finally, how do you know if your external rotation is good or bad? I always look at the total ark. If you are measuring both external and internal rotation a healthy range of motion is a total ark of 180. We can get this by adding external rotation to internal rotation.