Pronation & Spin Rate

             *Fair warning that this was pretty quickly written.  I've got 2 little boys (3 and 4 months) in the house with me so time is very limited. That being said, I will probably have to go back and make changes later.* 

             Near the end of my MiLB playing career, an idea popped into my head just before taking the mound.  I had always had a relatively “flat” fastball.  I threw 4 seam fastballs only.  I tried to throw a 2 seam fastball, but I never figured out how to make it move effectively.  Different grips, thumb placements & pressure points.  Nothing seemed to work for me.  Fortunately, in the Royals organization, we weren’t “allowed” to throw 2 seamers anyways.  On this particular day, I decided that I was going to try to forcefully turn my 4 seamer over to create movement.  7 years later (present day), this popped back into my head.  So naturally, the next step was to test out the effects of turning the ball over on spin rate.  Here’s what I found:.

            This test actually started out to see the difference in ball velocity, but the end result was an identical average velo for the 2.  This couldn’t have worked out any better for the sake of spin rate.  A little disclaimer: this was a very limited test.  It was conducted on just 1 athlete (or former athlete anyways) over 12 pitches done at sub-maximum intensity.  The average velo for both was 82.9 MPH.  The average spin rates, however, were much different.  The normal 4 seam fastball yielded an average spin rate of 2,041 RPM’s.  The pronated 4 seam fastball yielded an average spin rate of 1928 RPM’s.  Both are well below average MLB spin rates, but this is a very significant difference nonetheless.  To make up for being below average MLB spin rates, I turned to Driveline’s Bauer Units.  to get a better idea of exactly how significant the difference was. The average Bauer Units were 24.62 vs 23.26. 

            While trying to forcefully pronate at release, one thing I noticed was that it didn’t feel very consistent.  When looking back on the spin rates, it would appear to match what I felt.  Spin rates ranged from 1,722-2,028 RPM’s while velocity ranged from 81.4-84.3 MPH.  With the normal 4 seam fastball, spin rates ranged from 2,010-2,124 RPM’s & 82.4-83.1 MPH.  As you can see, things were much more consistent with the normal grip.  For me, this would mean that it’s hard to repeat the wrist placement at release when trying to pronate at release.  Ultimately, this would appear to be why the ranges are so wide.  The most interesting find may have been the fastest throw during the test.  The highest velocity came while turning the ball over at 84.3 MPH, but it also had the lowest spin rate (1,722 RPM’s).  The Bauer Unit of this particular pitch was 20.43, which would be remarkable to replicate at a higher velocity! 

It would appear that my hypothesis that turning the 4 seam over would lead to more movement based off of these findings, but again, this is a limited test.  It would still take a little more testing to see if this happens fairly consistently among athletes and would take better technology to determine exactly how much movement.  So anyone with the technology to do so, feel free to take over from here.