There are many variables that affect pitching velocity, but a highly valuable component is what is called hip and shoulder separation. Evidence has discovered that the timing of hip and shoulder separation will not only enhance pitching velocity but reduce arm stress (Dave, Glenn, & James, 2009). The reasons why hip and shoulder separation are so important is becomes baseball pitchers have a pattern of injury which is exposed when pitching velocity is increased. There is a high probability that this increase will lead to arm pain and even injury.
Hip to shoulder separation is when the hips have opened to the target and the shoulders are still closed the moment the front foot lands and stabilize in the pitching delivery. Elite levels of peak hip to shoulder separation are 60-70 degrees. I use a device called 4D Motion which is Bluetooth sensors with an IOS app that can measure this movement during the pitching delivery. In my training camps, I record this measurement for all my pitchers and post the data on TopVelocity.club.
Hip to Shoulder Separation Study
Here is a case study that found hip to shoulder separation was a good predictor of pitching velocity in youth pitchers (Sgroi et al., 2015). The study had a total of 420 subjects who were pitchers ages 11-19. The height of these pitchers was 55-75 inches. The average pitching velocity was 64mph with a standard deviation of 10mph. After multivariate logistic regression analysis, the most important correlates with pitch velocity were age (P < .001; R2 = 0.658), height (P < .001; R2 = 0.076), separation of the hips and shoulders (P < .001; R2 = 0.027), and stride length (P < .001; R(2) = 0.016); in combination, these 4 variables explained 78% of the variance in pitch velocity. Each year of age was associated with a mean 1.5 mph increase in velocity; each inch in height, with 1.2 mph; separation of the hips and shoulders, with 2.6 mph; and a 10% increase in stride length, with 1.9 mph.
This study is very important for the youth in the game of baseball. The reason is that very few coaches at the youth level understand what hip to shoulder separation is and its benefits. For the ones who do know the terminology very few know how to teach or train the movement. I have found it best to train this movement with a two-handed medicine ball throw that uses the same biomechanics as throwing a baseball. The reason it is so effective is that when you throw a ball with two hands through the pitching delivery it forces the hips and shoulders to separate or you can throw it straight. This is a great drill to teach and enhance the movement, especially at the youth level.
Hip to Shoulder Separation Reference
Dave, F., Glenn, S. F., & James, R. A., (2009). Baseball Pitching Biomechanics in Relation to Injury Risk and Performance. Sports Health, 1(4), 314–320.
Sgroi, T., Chalmers, P. N., Riff, A. J., Lesniak, M., Sayegh, E. T., Wimmer, M. A., . . . Romeo, A. A. (2015). Predictors of throwing velocity in youth and adolescent pitchers. Journal of Shoulder and Elbow Surgery, 24(9), 1339-45.