An Analytical Look at the Baseball Swing Plane

baseball swing plane

According to HitTrax, well-hit balls are generally hit within 24″.  On the other hand, a 93 mph fastball takes 1.585 milliseconds to travel those same 24” once it reaches homeplate.  We’re not dealing with a lot of time and every millisecond counts.  So, let’s review exactly what can happen during those 1.585 ms! First, let’s define the baseball swing plane and what it means to “be on-plane” so we’re all on the same page…

Being on-plane means matching, as best you can, your swing’s attack angle at the point of contact to the descent angle of the pitched ball.

General thinking is that being on-plane increases the amount of time you have to make good contact.  Everyone knows hitting is difficult… round bat, round ball, etc.  In this article, we’re going to take a purely analytical approach to reviewing:

    • Being “on-plane” at the moment of contact
    • The difficulties facing batters being generally “on-plane” from a statistical viewpoint
    • How one could improve their on-plane-ness

Let’s begin by reviewing the two angles and put some parameters around each:

Pitch Descent Angle – In a previous article (click here), we reviewed pitch descent angles.  Basically, it’s the angle at which the pitch is coming downward towards Homeplate. At MLB-level velocities, we are generally looking at a range of descent angles around 6 degrees for fastballs and 10 degrees for curveballs.  Let’s call this the “sweet zone”:

Pitch descent angle

Source: “Optimizing the Swing” in The Hardball Times (November 11, 2015)

The above estimates are based on MLB average velocities of 93-94 mph on the fastball and 77-78 mph on the curveball.  Given the relationship between velocity and descent angles, one could assume lower levels of play would have slightly higher descent angles, perhaps 7-11 degrees or more, as velos drop.  However, for the purposes of this article, we will stick with 6-10 degrees.

Attack Angle – Now let’s switch gears and look at distribution of attack angles from a recent study we did with college level players.  The following table provides a summary of average attack angles for 11 players (measured with the Blast Motion sensor after nearly 2,500 swings over a 4-week period):

baseball swing plane

To summarize, our college players have an average attack angle of 9 degrees with a standard deviation of 4.7 degrees.  For those that have forgotten their statistics 101, this basically means that assuming a normal distribution:

hitting attack angles

        • At -1 to +1 sigma, 68% of attack angles were between 4.3 and 13.7 degrees
        • At -2 to +2 sigma, 95% were within -0.4 and 18.4 degrees

Just in case you’ve forgotten your statistics, here is another way to look at the data for each player.  Once again, very wide ranges:

baseball swing plane

Baseball Swing Plane, On-Plane, Under- and Over-

Now, let’s consider three different circumstances and how each may influence being able to make good contact:

    • Swinging On-Plane
    • Swinging Under-Plane
    • Swinging Over-Plane

Swinging On-Plane (Average AA: 9 degrees) – If one had a 9-degree average attack angle, most would believe that such a player’s swing is on-plane with most incoming pitches. Unfortunately, as we reviewed earlier the average doesn’t tell the whole story.

If you look closer at the standard deviation of players’ attack angles, you would quickly notice that our average college player is off-plane quite a bit.  In a game of inches, at 9 degrees you will still spend quite a bit of time off-plane.

Having said that, it’s obviously much better to have your attack angle in the “sweet zone” (defined earlier as 6-10 degrees).  You can match planes across a variety of pitch types, from a fast ball in the top of the zone, to a big hook coming in at the bottom of the zone.  But this quickly changes as soon as you leave this sweet zone.

blank

Swinging Under-Plane (Average AA of 4 degrees) – With an average attack angle of 4 degrees (below a typical MLB fastball of 6 degrees), in the chart below you can observe the substantially reduced amount time a player would spend on-plane.

In addition, if you spend quite a bit of time that far below the sweet zone, you might hardly ever get on a plane with a curveball on the right-hand side of the chart.  You could likely have more difficulty with curveballs.

blank

Swinging Over the Plane (Average AA: 11 degrees) – Now let’s take it to the other end and put your average attack angle at 11 on the right-hand side of the chart.  You can see the opposite begins to happen as you spend minimal time being on-plane with fastballs.  Those with higher attack angles could have difficulty hitting fastballs, especially up in the zone.

blank

Summary

Being on-plane with the variety of incoming pitches is a function of two things:

    • Your average attack angle vs. the sweet zone
    • Your standard deviation (swing variability)

If the objective is to be on-plane, then you would want to:

    • Develop an average AA in the high single digits
    • Achieve as low a standard deviation as possible to reduce swing variability

The second point is perhaps just as relevant as the first! A lower standard of deviation will allow for less baseball swing plane variability which in turn could allow for a bit more flexibility on your average AA vs. the sweet zone.

Even within our small group of college athletes, 2 players had standard deviations near 3 degrees.  I can only imagine what a big leaguer’s standard deviation could be, perhaps approaching 1-2 degrees?!  In a recent podcast a representative from Blast Motion mentioned that the average attack angle in MLB is 8 degrees.  If you put that together with a low standard deviation of 1-2 degrees you can substantially improve on your on-plane-ness!

baseball swing plane

You might ask why fuss over a few degrees here and there.  Well, we are talking about a ONE-TWO milliseconds, aren’t we?

By Bahram Shirazi (Co-Owner RPP, BSEE, MBA)

Please feel free to add your name to our email list below!