Introduction to Baseball VMI - Welcome!

Posted: 2024-03-28 07:22:07 (ET)    [ 825 views ]

If you are relatively new to BaseballVMI, the following may move you along a little faster in your studies:

Let's talk about Air Density as related to baseball hitting and pitching.

What causes air density to change?  Air becomes thinner as the elevation increases.  It also becomes thinner as the temperature goes up.  As the humidity percentage increases the air density actually gets thinner (or lighter) as well. Why? Because there is more hydrogen in humid air and less nitrogen.  Yes, high humidity feels sticky, but it is not heavier for a baseball to push through.

So, in thin air in Denver in the 90 degree temperature ranges the air is very light, so a baseball can push through the air more easily and therefore curveballs get lesser bite against the air.  This fact is the same with fastballs and every other pitch.  However, at sea level and closer to sea level, the air is heavier because of the altitude and in cooler temperatures, but rarely is there lesser humidity at sea level.  Humidity does not have much effect on how a baseball flies at either end of the altitude spectrum for MLB pitchers.

For more information about the air density and the Air Density Index (ADI) see both the Neeley Scale on the Home Tab and the Science tab on this website.

Why do we refer to movement on a fastball as being "Lift?"

To baseball players, lift just means the Fastball, for example, just stays straighter in its path all the way to the strike zone.  However, to engineers, physics educators, aeronautical professionals and other academians, lift means that the air density  holds the pitch up from dropping as much as it would without the air.  That is because the fastball is spinning backward and the threads are whipping against the air to hold it up longer.  At all speeds, thinner air will allow it to drop more in its arched travel than it will when pitched in more dense (colder, sea level) air.

However, there is a much more complicated matter which is only identifiable by the hitter who is tracking a 95 mph fastball and has experience hitting it.  The issue is the last several feet of travel at high speed that holds the ball up and causes more sideways "tail-off" than the hitter is used to seeing daily.  The difference in that last few feet can be as much as 4 inches higher at the same speed than in the thin air of Colorado and an additional 5 inches sideways.  So, this is not a small issue for hitters who begin a road trip from Colorado, Phoenix, Atlanta and/or, if MLB puts a team in Las Vegas, any team leaving that location, as well.  It does take about three full games of exposure to the best movement in MLB for any hitter to adjust, and by that time, he has lost confidence which complicates the adjustment.  See data of results we have recorded in terms of hits/strike thrown on almost 6 million pitches in MLB over the past 9 seasons of not only the home team, but visiting teams leaving after a series at each ballpark.

The data below can be seen in individual seasons on this website under "Sortable Stats"

Pitch vs. VMI
Start Date:   1-1-2014

End Date:  1-1-2023

Team:       All Teams
Venue:     Both Home and Road Venues
Pitch:       All Pitch Types Included
VMI Interval:    10    -    On the website query you can see data as minimal as 1.00 VMI differential in atmospheric conditions at game time for the hitters and pitchers.  You only need to select the VMI Interval that you choose.

 
Plus VMI Ranges = Hitter's Eye (or, Expectation) Above Center
                                          Pitches                              Strikes                        Hits                    Percent        

+0.00 thru +9.99             2,957,760                        1,874,031                   173,908                    9.28 
+10.00 thru  +19.99             74,504                             47,030                       5,136                   10.92 
+20.00 thru +29.99              24,207                             15,269                       1,687                   11.05  

                       Total        3,056,471                         1,936,330                    180,731                 9.33%     

Minus VMI Ranges = Hitter's Eye (or, Expectation) Below Center

                                          Pitches                              Strikes                       Hits                     Percent        

 - 0.00 thru - 9.99             2,832,056                        1,794,566                    158,900                   8.85 
-10.00 thru -19.99                 83,883                             53,292                       4,459                    8.37
-20.00 thru -29.99                 17,274                             11,085                          893                    8.06

                      Total          2,933,213                        1,858,943                    164,252                   8.84%

QUESTION:  Would you rather be a hitter at Plus 20 VMI  or  Minus  20 VMI?

                               Which VMI would you rather pitch within?

  
Total Pitches:      5,968,885        Total Strikes: 3,782,101      Total Hits: 343,767    Total Percent:           9.09%


NOTE: 20,799 pitches of exactly 0.00 VMI are shown in both + and - VMI columns.

Which Pitches favor the pitcher in Heavy Air and which in Light Air?

The objective of this section is to help you gain insight into "when" teams and individual players will be more effective.   If you know the VMI, then you know the hitter's set-up tendency for today, and you will have a clearer picture of the hitter's capability to adjust to a particular pitch.  For example; if the "tail-off" on the 95 mph Four-Seamer is lifting (or staying straighter) by 4 inches today at a 65 ADI (Neeley Scale) as shown on the charts under "Pitch-Mix" on this site, but the hitter is used to more than that amount and sports a +4.00 VMI today, then the following should be a tip for you, or the pitcher, or catcher:

This hitter may be more susceptible to being induced into a groundball with the two-seamer or cutter.  This is because his set-up (that is; his swing vs. what he sees) will be above the four-seamer's tail-off and fully prepared to meet that lifting pitch upon its arrival at the zone.  Two-seamers and cutters however, lift less than the hitter is expecting from the four-seamer for which he is most often prepared.   In this case, he will need to bring the bat further downward to hit it and most likely will result in a groundball until the adjustment is complete by about game 3 in that same, or a similar climate.

Everyone in baseball knows why and how to use two-seamers and cutters, they just don't always know "when," as there has never been an analysis of how players react to the physical properties of the air.  It is the air which causes late movement and allows further analysis of hitters' preparation when gauged as in the ADI and VMI.

Now, imagine the opposite scenario, whereby the hitter is not used to that amount of movement, but has been playing in about 59 ADI.  His VMI will be as great as -4.00 or greater negative, therefore his setup to swing will naturally be a little below the center of the four-seamer until he adjusts.  Therefore, those hitters on that imagined team, will probably hit more pop-ups than normal until they adjust.

This team's hitters would tend to be more dangerous against the two-seamer/cutter, because the set-up is closer to where the hand-eye coordination needs to be to hit it on a line.

Under "Pitch-Mix" on this site, there is a more detailed description of each VMI range and each type of pitch.  Also, there are some previous blog articles you can access by scrolling down on this blog page. 

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