More on brush resistance--highly technical

Welcome to Discuss Fastpitch

Your FREE Account is waiting to the Best Softball Community on the Web.

sluggers

Super Moderator
Staff member
May 26, 2008
7,132
113
Dallas, Texas
JV gave a nice description of the technical mechanics behind the arm motion.

Basically, the pitcher by changing the configuration of the arm (i.e., the amount of bend in the arm), the pitcher increases the RPS (AKA, angular velocity) of the arm.

However, to change the increased RPS into an increase in the linear speed of the fingers at release, the upper arm has to be slowed down prior to release. (If the upper arm isn't slowed down, the speed of the arm will decrease.)

A pitcher slows the upper arm down by a combination of (1) the shoulder muscles and (2) brush resistance.

The more brush resistance, the less work the shoulder muscles have to do...which means the shoulder muscles will last longer. (Of course, that is at the expense of pounding the arm on the hips...but most women have extra padding on the hips.)

I'm wondering if brush resistance reduces injuries to the pitcher's shoulder.

JS, what do you think? I'd love to have Rick weigh in on this...but I think he is tied up with his new job.
 
Last edited:

JJsqueeze

Dad, Husband....legend
Jul 5, 2013
5,436
38
safe in an undisclosed location
JV gave a nice description of the technical mechanics behind the arm motion.

Basically, the pitcher by changing the configuration of the arm (i.e., the amount of bend in the arm), the pitcher increases the RPS (AKA, angular velocity) of the arm.

However, to change the increased RPS into an increase in the linear speed of the fingers at release, the upper arm has to be slowed down prior to release. (If the upper arm isn't slowed down, the speed of the arm will decrease.)

A pitcher slows the upper arm down by a combination of (1) the shoulder muscles and (2) brush resistance.

The more brush resistance, the less work the shoulder muscles have to do...which means the shoulder muscles will last longer. (Of course, that is at the expense of pounding the arm on the hips...but most women have extra padding on the hips.)

I'm wondering if brush resistance reduces injuries to the pitcher's shoulder.

JS, what do you think? I'd love to have Rick weigh in on this...but I think he is tied up with his new job.


Actually, the upper part of the compound pendulum slows down due to the reaction forces of transferring energy to the next linkage, in effect the next linkage needs something to "swing against" so it speeds up while the previous linkage slows down. The shoulder does not muscle it to a stop or force the slow down. This is why the looser the arm is the better whip you get. The brush does enhance this effect by putting a bit of a physical barrier to rapidly decelerate against and add that last little burst of acceleration just before release.
 
Dec 5, 2012
4,143
63
Mid West
Gotta agree with jj on this one. I do not condone a physical banging of the elbow into the ribs or hip. If the ball is oriented upward at 9:00 the energy will naturally transfer into the lower half during IR. Brushing, while does reduce a bit of speed in the upper arm, I believe its more so for circle consistancy and maximizing the whip. JMHO...James
 
Apr 5, 2009
748
28
NE Kansas
And the more stable the "something to swing against" is, the easier it is for the energy to be sucked out of the fingers, using BM's analogy. You can park your car fast or slow, just don't leave the back-end out in traffic for the guy behind you to crash into or bump off of.
 

javasource

6-4-3 = 2
May 6, 2013
1,347
48
Western NY
I'm wondering if brush resistance reduces injuries to the pitcher's shoulder.

JS, what do you think? I'd love to have Rick weigh in on this...but I think he is tied up with his new job.

Oh boy... the brush subject. I can hear grumblings in left field forming... ;)

I'm glad JJ chimed in. Despite telling everyone he slept through classes, that cat knows a good deal about this stuff.

Although I would agree that in learning this stuff, it's best to keep it "loose as a goose"... but at some point, you need to make it "full of juice".

Full-speed pitching is pretty 'powerful'... and has much more muscle deceleration than we would think. Abduction and extension torques are generated at the shoulder to aid in transferring energy to the forearm and initiate the deceleration of the upper arm, prior to 'brush'.

Chaining is all about proper timing/sequencing, no doubt. But, I remember the first time I read about it in a class...and writing something to the effect of:

Since distal acceleration occurs only after the proximal segment reaches maximum speed... would it be safe to assume that the reason for chaining is:

1) That the proximal segment cannot maintain maximum speed... it's a point to be reached. Beyond that point of maximum speed, it only gets slower...

2) ... so... since the proximal segment has an attachment (more distal component/lever)... this is the reason that the attachment will start to accelerate... that is, because the proximal segment can't get faster, only slower.


I thought I had it all figured out, until I saw that I got an 80% on the assignment. In the comments, the teacher said he would've given me a 75... but the enthusiasm I wrote with gave me an extra 5 points. The reason I was only given three-quarters credit, is that the human body is not as simple... and I failed to make the correlation as it relates to "something of greater detail than a 6th grade science project". Those aren't my words... I still have the paper... even after trying to burn it with my solar cooker. ;)

Anyway... shoulder extension torque being reached, initiates elbow flexion and allows energy to be trasferred - as talked about in the other thread Sluggers mentioned. After shoulder extension, the teres minor becomes a big player in decelerating the humerus.

In regards to Sluggers question...

Yes, contacting the thigh does. The lats, scaps and pecs work to adduct and flex the arm into the side... or until contact with the lateral thigh. Perhaps we start calling brush 'lateral thigh contact'... just to confuse the hell out of all the haters...

Anyway, there have been studies that included measurements with lateral thigh contact as well as studies of those that didn't use it.

In pitchers that used 'lateral thigh contact' ;) , deceleration forces and torques - that are generated by the arm in an effort to slow down the arm - were "much less" than observed in studies where no lateral thigh contact was made. All collegiate pitchers used this mechanism of deceleration, whereas in the other study... none of the youth softball pitchers did. As such, the shoulder forces - like compressive forces and torques were much greater in those that did not contact the lateral thigh.

This may explain another theory I have... which is: "Why do some high school coaches refuse to acknowledge brush?" My thoughts are that they aren't exposed to brush, as it's a trait of high-level pitchers, and not necessarily prevalent in recreational and high school pitchers. ;)

Another aspect of lateral thigh contact... is that it lessens the torsional forces experienced in the forearm, too. Even though it's biomechanically advantageous to pronate the forearm during the release phase, lateral thigh contact can significantly dampen the effect this stress can have on the forearm. Injuries of this type are incredibly rare... having more to do with underlying pre-existing conditions than the movement itself... but just thought I'd throw it out there...
 
Last edited:
Jun 18, 2012
3,183
48
Utah
OILF, I just love your choice of words in this regard brush interference--"hitting"

I can only imagine how much better those pitchers you speak of would be with a little BRUSHING of their hip with their forearm.

Further, I would love to see clips of each and every one of those pitchers you are directly involved with so that the people here might analyse their pitching style. How'bout it?
 

javasource

6-4-3 = 2
May 6, 2013
1,347
48
Western NY
If it were a faulty premise, it would never have received approval... nor would it have been published... nor would it have led to subsequent studies... and I would not offer it up for discussion now. These are things that really happen, by people that really do it, and studied/presented by and to a community that understands it. I believe that constitutes what some refer to as factual representation. Those aren't fighting words, either... so don't misinterpret the intentions of my response...

The forearm contacts the thigh... to answer your question, OILF. I posted some vids of pitchers doing it in the WCWS... can't recall the thread, but it's relatively recent... if you care to review it.
 

sluggers

Super Moderator
Staff member
May 26, 2008
7,132
113
Dallas, Texas
JS....thanks, I think I understand brush interference. It took me a while to understand "why" it works. Rick P. is convinced it adds speed. So, if it adds speed, then there has to be a reasoned explanation as to why it adds speed.

I think I got it...thanks so much.
 

Forum statistics

Threads
42,830
Messages
679,473
Members
21,443
Latest member
sstop28
Top