***NOTE: This thread will be heavily moderated until we get the beginning content right. Please contribute your own suggestions to this initial post as well as videos, GIFs, and other comments.***
CONTRIBUTORS TO THIS THREAD:
1) WHAT IS BRUSH INTERFERENCE?
Brush interference is contact of the throwing arm with the hip prior to release.
2) DOESN'T CONTACT WITH THE BODY SLOW THE ARM DOWN?
Yes, it does.
3) IF A PITCHER SLOWS DOWN THE ARM, THEN DOESN'T THAT SLOW DOWN HER PITCH?
No, it does not. Pitching can be though of in many ways, but usually the best way to think of pitching is momentum transfer.
If the upper arm is slowed down, the momentum from the upper arm will be transferred to the forearm, resulting in increased speed of the ball at release.
4) DOESN'T HITTING THE BODY REDUCE ACCURACY?
No. It increases accuracy. This is also counter-intuitive.
In order to throw the ball accurately, the release point of the ball has to be precisely controlled. When the arm contacts the hip prior to release, it provides tactile feedback as to the location of the arm. Based on the feedback, the pitcher can precisely control the location and time she releases the ball, leading to increased accuracy.
Or, to put it another way, a pitcher using brush resistance develops a reflex to the arm touching the body. In response to the brush, the pitcher releases the ball a few milliseconds later. This allows a pitcher to become incredibly accurate.
5) HOW DO YOU TEACH BRUSH INTERFERENCE?
First, a teacher needs to be aware that brush interference (BI) is good. If a pitcher is brushing her hip, then don't stop her.
Second, brush interference is a matter of posture. A pitcher should stand up straight.
6) HOW DO YOU KNOW IF THE PITCHER IS USING BRUSH INTERFERENCE?
Slow motion video helps. But, if you stand close to the pitcher, you can hear the arm make contact with the hips.
7) HOW DO YOU KNOW IF THE PITCHER IS NOT USING BRUSH INTERFERENCE?
The most common sign is the "butt out" posture of a pitcher. The pitcher will move her buttocks out of the way. She will then lean her upper body over to throw the ball.
8) DO ALL ELITE PITCHERS DO THIS?
The "best of the best" use brush interference.
There are some D1 pitchers who do not. The easiest way to find non-BI pitchers is to simply look at their walk totals. A BI pitcher averages around 1 walk per game. A non-BI pitcher will average around 3 walks per game.
9) WHO INVENTED BRUSH INTERFERENCE?
It was not invented.
Rick Pauly, from careful study of the best pitchers, found that they used BI. He then coined the phrase.