Today, we’re going to cover the topic of a baseball’s Total Spin rate vs. True Spin rate. We’ve previously reviewed how all spin is not alike, as some spin works for you to create movement and some spin doesn’t do anything at all. At any given moment, a baseball is likely spinning along all 3 axes at the same time. We’re talking a little bit of:

1. Left or right,
2. Backspin or topspin, and
3. Spinning around in one, or the other, direction (like a football spiral spin also referred to as gyro spin).

However, as we reviewed earlier, the component of spin that spins around like a football and is perpendicular to the direction of travel (#3 above) doesn’t contribute to a baseball’s movement as it travels towards home plate. And this leads us to the concept of True Spin which is a piece of data provided by the Rapsodo Baseball camera system…

True (Useful) Spin Rate

True Spin (or Useful Spin) only reflects the components of spin that contribute to movement. For example, a fastball may have a total spin rate of 2,200 rpm. However, after a little bit of analysis, we may realize that 500 rpm of that total spin is perpendicular to the direction of travel (#3 above). Once we remove that component, we are left with a True Spin 1,700 rpm. Here is a visual…

Now with True Spin behind us, we can review what Rapsodo refers to as the Spin Efficiency %, which is simply True Spin divided by Total Spin. It represents the % of total spin that is contributing to a ball’s movement. Below are examples of Total Spin, True (Useful) Spin, and Spin Efficiency % by pitch type:

In the chart above, a curveball with a total spin rate of 2,475 (rpm) and a True Spin rate of 1,490 (rpm) would have a spin efficiency of 60%. Said differently, only 60% of the total spin on this curveball is contributing to its movement away from its expected path. However, it’s important to note:

A lower Spin Efficiency % doesn’t necessarily make a pitch better or worse… It all depends on the type of pitch…

Below are examples of True Spin % vs. Football (Gyro) Spin %, with the slider having the largest component of the Football Spiral Spin:

So, low spin efficiency by itself is not a good or bad thing. It simply explains the difference between different types of spin and gives you an important piece of data for comparing one pitch to another.

As we covered in an earlier blog (click here), it may be difficult to adjust the spin rate on your 4-seam fastball but you can certainly work to make adjustments on your secondary pitches. Using the above table is great guideline for pitchers to assess their pitches, and perhaps adjust their finger pressure / grip / mechanics to increase or decrease spin rate / movement. The idea behind all this data is to better understand why the ball moves, what makes it move and what you can do to improve on that movement.

By Bahram Shirazi (BSEE, MBA, Co-Owner RPP)
Robbie Aviles (RHP Cleveland Indians, Pitching Lab Coach)