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Spin: The Reality and Deception that is Helping or Hurting Pitchers.

July 25, 2016


A pitcher can do anything and everything before and during his delivery to prepare himself to throw the best pitch he is capable of. At the very moment he releases the ball, all he can do is hope it misses a barrel. Other than funky deliveries and peculiar body shapes, what contributes to the effectiveness and deception of the pitch? Once the ball leaves the pitcher’s hand physics takes over and the ball begins to spin.


Every pitch’s spin rate can be precisely quantified by determining how many times the ball rotates around its axis. The measurement for this is labeled as revolutions per minute (RPM) or magnitude. Many outside factors such as gravity, drag force and magnus force affect the RPMs of a pitch. Gravity effectively forces the ball in a downward motion once the ball is in flight. Drag is an aerodynamic force that occurs in all objects in motion. The fastest a pitch will ever travel is when it is first released from the pitcher’s hand. That point of peak velocity is known as muzzle velocity. From there, outside forces act upon the ball while the ball pushes the air out of its path incrementally decreasing the velocity of the ball. This process is known as drag. It is essentially the aligned and opposing air that retards the velocity of the pitch. The shape, size and velocity of the ball, as well as the density and viscosity of the air affect drag force. Magnus Force is present on all spinning pitches and is responsible for the break, curve, and trajectory of the ball. For example, a traditional four-seam fastball thrown with true backspin will have an upward pushing magnus force (opposing the downward forces of gravity) thereby delaying the effect of gravity. We will look more into magnus force as we progress through the article.



Why Should You Care about Spin Rate?


Outside of raw velocity, spin may be the most significant consideration when developing your identity as a pitcher. I’m a big fan of power pitching and the excitement that velocity brings to the table, but fastball velocity may not always be the biggest contributing factor to getting outs. You may be asking yourself if spin rate is a contributing factor to velocity and the answer is no. Spin rate acts independent of velocity development, yet is heavily dependent on fastball velocity, which you can see in MLB’s very own 2015 Statcast chart below.





The same type of pitch thrown with the same velocity can yield vastly different spin rate results. Well, what does that mean? Is a higher spin rate better? Is it worse? What happens because of it? 

Spin rate not only affects the flight and trajectory of the pitch, but it also affects the manner in which that ball is hit. Fastballs with higher spin rates yield higher fly ball percentages and account for more swings and misses. Fastballs with lower spin rates yield more frequent ground balls. Interestingly, fastball and curveball spin rate ratios do not produce the same frequency of result. As aforementioned, fastballs with higher spin rate produced a higher frequency of fly balls, while curveballs with high spin rates produce a higher frequency of ground balls. Why is this? Fastballs (thrown with top spin and a magnus force pushing upwards) with higher spin rates defy gravity longer and do not move downward as quickly as fastballs with average spin rate often causing the batter pop up. A curve ball (thrown with top spin and a magnus force pushing downwards) with a high spin rate travels downwards more rapidly causing the ball to get under barrels forcing groundballs.  Just as a fastball with low spin rate produces ground balls due to it’s sinking nature, a curveball with low spin rate (a weaker magnus force) tends to induce more fly balls because the magnus force does not push the ball downwards as rapidly.


The total spin of a pitch is comprised of two categories: useful spin and gyro-spin. Useful spin increases movement of the ball and influences the ball to move in the direction it is spinning. Gyro spin is referred to as “bullet spin” and does not account for much movement at all. A gyro ball is a spiral like pitch and has no magnus force when crossing the plate as its spin axis is directed forward. Spin rates and spin axis orientation greatly differ with each pitcher; yet do not affect the velocity of the pitch.



                                    2015 MLB Spin and Velocity Averages


Since Spin Does Not Affect Physical Velocity, Does Spin Affect Visual Velocity?


Absolutely! We’re all familiar with the Batters who come back in the dug out after at-bats and tell tails of how a particular pitch is sneaky quick, or that it rises, or that it jumps at the end. In the more advanced baseball ranks, the optical illusion of a rising fastball is referred to as “ride”. In order for a pitch to actually rise, the magnus force of the pitch would have to exceed the force of gravity, which is beyond unlikely.

Often, baseball folk label curveballs and sliders as “spinners”. The spin on those pitches influence the ball to move in the direction of the spin, around the axis of the ball. Since a traditional 12-6 curveball has pure top-spin, with a magnus force pushing the ball downwards, the ball ends up traveling downwards. Wouldn’t that same principle apply to a four-seam fastball with true backspin? Wouldn’t the spin and magnus force that is pushing up cause the ball to rise? Not quite.

When the ball is released from the pitcher’s hand there are forces acting upon the ball. Keep in mind that gravity is one of those forces, thereby, influencing every pitch to begin it’s descent once it is released and in flight. Having said that, when predicting trajectory of a pitch, it is important to account for the magnus force of a four-seam fastball. Essentially, the four seamer’s magnus force is pushing the ball upwards, whereas, gravity is pushing the ball downwards. Consequentially, as the counter acting forces take way, the power struggle between the four-seamer’s magnus force and gravity causes the fastball to drop at a less rapid pace. A 92 MPH fastball thrown with a magnitude of 2,300 RPM will cross home plate slightly higher than a 92 MPH fastball thrown with a magnitude of 2,100 RPM. As a rule of thumb, as far as fastballs go, a pitch thrown with more magnitude (a stronger magnus force) will carry it’s trajectory better and will fall less than a pitch with a weaker magnus force. Therefore, a fastball (with a higher than average spin rate) will look like it is rising, but in actuality, it is merely dropping less than most fastballs with average spin rate. This is known as “riding through the zone”.


A study in Japan, at Waseda University, confirmed the stark contrast between an 87 MPH fastball with 2,400 RPM and an 87 MPH fastball with 1,800 RPM. In the study, the fastball with 2,400 RPM crossed home plate roughly 70 millimeters above the fastball with 1,800 RPM, which is roughly a full baseball above the other crossing spot. In this instance, although the difference of locations is only the size of one baseball, to a batter’s instinctual, computational brain, 70 millimeters makes a world of difference.



What is a “Heavy Ball”?


A heavy ball is not a ball that is thrown hard with high velocity nor is it natural phenomena created by some pitchers affecting the weight of the ball. A heavy ball is simply a ball that is thrown is a low spin rate. Fastballs with low spin rates are often accompanied by sink or added depth which may contribute to the catcher receiving the ball more towards the palm, rather than the pocket of the glove. Hence, at times making the ball feel heavy.


Determining the Spin Axis of the Pitch.


The spin axis is simply the axis in which the ball rotates around. Alan Nathan, Professor Emeritus of Physics at University of Illinois Urbana- Champaign, has proposed an easy way to determine spin axis and axis orientation that he calls the “Right Hand Rule”. Professor Nathan describes the protocol by “wrapping the fingers of your right hand around the ball so that they point in the direction the ball is turning. Your thumb will then point in the direction of the spin axis”. Generally, the spin axis is perpendicular to the direction of spin. For example, a conventional over the top RHP throwing a true four-seam fastball will have a horizontal spin axis directed to the right hand side. A sidearm pitcher who throws a true “Frisbee slider” that laterally sweeps across the plate will have a vertical spin axis directed upwards. Granted, how often do pitchers actually throw pitches with perfectly true backspin or topspin? Alm

ost never, but this is still a serviceable way to determine general axis without technology.



Can you Manipulate Spin Rate?

Many people propose different ways to lower spin rate to get more depth or sink on a fastball. The fact of the matter is as much as we need answers, we may not even be asking the right questions yet.


Without altering a pitcher’s delivery, a quick way to generate less magnitude (less RPM) is by altering the type of fastball from four-seam to two-seam/sinker or simply spreading your index and middle finger apart. Our anecdotal work with Rapsodo has supported this claim, but it is nothing more than a theory at this point. As we just pointed out, many folks suggest spreading or splitting your fingers across the ball (rather than placing them together), which will, in turn, lower the natural backspin of the ball and directly affect the net force applied to the ball. Inversely, when throwing a fastball, some would suggests that if the pitcher places his fingers together he may increase spin rate. Yet, placing his fingers together would not necessarily increase his spin rate; rather, the best claim one could come up with at this point would be that it would allow him to reach his RPM ceiling for that given pitch by applying a more singular point of pressure and affecting the net force of the ball. We are not sure what all the variables affecting spin rates are ( just yet)but whoever is the first to realize that will drastically affect the game and pitching as we know it.


 Split-Finger fastballs are known for their uncanny nature to “drop off the table” at a slightly lower velocity. We know that the positioning and space of the index and middle fingers affect the RPM of the pitch, but what is magnitude and movement’s relationship with the thumb? Does thumb placement (on or off the seam, high or low on the seam) affect movement or magnitude? Although I am sure thumb placement yields results and affects the flight of the ball, I cannot, for certain, propose a concrete effect. Before writing this article, I consulted with one of the country’s most reputable private pitching instructors who asked to remain anonymous. During the course of our conversation, he asserted that dependent on arm slot, wrist action, index finger position, etc., thumb placement higher on the side of the ball derives more run (lateral movement) and thumb placement below the ball induces more sink (depth). Further, mentioned Greg Maddux used to move his thumb a few stitches up or down the seam during each inning based on how much movement he wanted. Pretty neat, huh?


So, can spin rate be affected, manipulated or taught? Absolutely.  Can spin rate will effectively taught or manipulated yet? Not yet. Can curveball and slider spin rates be raised? Yes. Do we have confirmed and extensive ways to teach spin rate manipulation? Yes and no. Much more research is being done everyday on spin and it’s variables. Proper training and execution are also contributing factors to affecting spin rate. It is a very exciting time to be a ball player, especially if you’re interested in spin rate and other quantifiable measurements in baseball.



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