Speed of forearm pronation/supination

I believe it's in one of the early posts in the I/R in the Classroom thread - there's a statement made (by BoardMember, IIRC) that the pronation/supination movement of the forearm is the fastest body movement.

I spent a good deal of time trying to verify that statement, learning about linear velocity, angular velocity, the actual speed of "a blink of the eye" (much slower than you'd think), but nothing confirming the above statement.

We have our first rec team practice for the Fall tonight (finally!), and was going to try and use the demonstration of showing the kids (and parents) how much faster they could "spin" their wrists and forearms (IR), compared to the speed of flexing your elbow and wrist when using HE mechanics.

Can anyone point me in the right direction? I really, really doubt anyone's going to ask me to cite a reference, but I also don't want to be dispelling one myth by creating another one.

Thanks for the help,

Gags

https://www.nsf.gov/news/news_summ.jsp?cntn_id=128399
This article talks about the shoulder and the internal rotators. People who teach poor mechanics only see linear speeds... but the true speeds come from the angular accelerations that occur as a result from the summation of linear and rotational forces, and the application of kinetic transfer.

So... if IR is as fast as people in Harvard say... then the summation of forces in the forearm are THAT... PLUS the rotational forces added by the pronator teres.

To put it in perspective... a 75 mph pitch means that the hand was at 75 mph at release...

... whereas the blink of an eye takes 3/10 of a second... may seem fast... but if you convert the distance the eyelid travels (probably a couple centimeters) in that time... you're probably looking at 10-15 mph.

So... the summation of speeds is all that really matters... and they are at times, 6-7 times faster than a blink of an eye.

In other words... if you blink when Monica Abbott releases the ball, you would miss ever seeing the ball.

javasource, there are a couple of problems with your determining the speed of the ball compared to the blink of the human eye. The iris is anywhere between 2 and 7 millimeter is diameter, you can't use the size of the entire eye in your determination. More important, the only thing relevant about the eye is the duration of the blink. Since 75mph is equivalent to 110 feet/sec, in .3 seconds a ball at that speed will travel 33 feet. Granted, with a Monica Abbott fastball, if you blink you will see it for less than a quarter of the time it is heading towards the plate. This is falsely assuming her fastball does not slow down. In any case, don't blink.

Bob,

Hmm... I assume this is just a good-natured ribbing... so, for the purpose of conversation (my apologies to the OP):

Bob516 said:

... you can't use the size of the entire eye in your determination.

Click to expand...

Why not? A blink - as I know it (and I'm ok with being wrong) is the closing and opening of the eyelid. So... it would have to close... covering the whole eye and then open. Unless we partially blink... to which I have no clue???

blink
bliNGk
verb
1. shut and open the eyes quickly.

Bob516 said:

More important, the only thing relevant about the eye is the duration of the blink

Click to expand...

Speed... which is what I was comparing... is distance over time. So... the distance the eyelid travels is half the equation, and quite relevant.

Bob516 said:

Since 75mph is equivalent to 110 feet/sec, in .3 seconds a ball at that speed will travel 33 feet.

Click to expand...

Yep. She probably releases the ball at 38 feet... so I guess that gives them a few hundredths of a second to find, focus, and decide.

Bob516 said:

This is falsely assuming her fastball does not slow down.

Click to expand...

Nah. The time to plate is .38 seconds with a release velocity of 75 and a distance of 38-feet (43-5). In New York City, and a hot day. And that calculates an instant speed loss, too. (67mph at plate).

My point... and this goes towards all the recent HE posts... is that the speed of the ball is highest when you consider/train the culmination of angular and linear forces at the end of the kinetic chain... when compared to the absurd construct of locking the arm out with palm-down at 10... solely depending on elbow and wrist flexion for speed.

I think ole' coffeeking is trying to get his post count up in an attempt to make the ballot for the yearend DFP Posty's Award Show... Two posts in just one day? Not gonna cut it! @javasource








(The geezer just called javasource old... Ha!)

javasource said:

Hmm... I assume this is just a good-natured ribbing... so, for the purpose of conversation (my apologies to the OP):

Click to expand...

My apologies to the OP as well (see below). Yes, just good-natured ribbing, and a meaningless intellectual debate.

As to the blink, the only relevant part of the blink to the discussion of seeing the ball is the time the eye lid covers the pupil, where light enters the eye. The time the eye lid moves over the iris and white of the eye is irrelevant to how long light is blocked from entering the eye, and since the pupil is a fraction of the size of the eye, it is significantly less than .3 seconds. So if your discussion is "if you blink when Monica Abbott releases the ball, you would miss ever seeing the ball," then no, the duration a her pitch from her hand to the catcher's mitt, or plate, is longer than the time the pupil is being blocked by the eyelid. If you argument is that the eye lid moves over the entire eye slower than a Monica Abbott fastball, then yes, a 75 mph fastball gets to the plate in .38 seconds, covering 38 feet, which is faster than the eye lid moving over the entire eye in .3 seconds.


Now to try to honor Gags original question, I found this from the Journal of Orthopaedic & Sports Physical Therapy-Biomechanics of Windmill Softball Pitching With Implications About Injury Mechanisms at the Shoulder and Elbow, https://www.jospt.org/doi/pdf/10.2519/jospt.1998.28.6.405?code=jospt-site.

If I understand IR correctly, and that is a huge assumption as I am brand new to fastpitch pitching, this illustration from the Journal seems to be IR,



If this Journal is using IR to illustrate the study of windmill pitching, I would think it might be safe to assume it is fastest, or at least the preferred way to pitch a softball underhand. Does not exactly answer your question of whether it is fastest movement of the body, but I think it lends credibility to your discussion.

Good luck with your demonstration.

Bob - thanks for the link. Will take a look.

Edited to add:

Came across this page in my initial search for "fastest body movement" - so since we're also talking about eyeballs/eyelids:

Quote:
Originally Posted by njtt [...]Saccadic eye movements reach rotational speeds (rotation of the eyeball) of about 500º per second. I am not sure how to translate that into mph, though.

Click to expand...

Eyeball is about 1 inch in diameter, which makes it about 3.14 inches in circumference. So...

360 degree = 3.14 inches

therefore

500 degrees = 4.36 inches

500 degrees per second = 4.36 inches per second

4.36 in/s = 0.248 miles per hour. That's...really not all that fast.

Click to expand...

While the above is talking about eye movement, and not an eyeblink - it's an interesting way of converting speed. I'm probably going to botch this, and will be using the "WAG" method for my assumptions - but if the eyelid covers about 45 degrees of the eye per blink, or maybe - 90 degrees (down and back up) - and using the above circumference of 3.14", then:


No idea why I just wasted time figuring that out - maybe someone can use it to win a bar bet.

But I agree with Bob - if you're ever in the batters box facing Amanda Scarborough, don't blink!

Although thinking about it a little more - my chances to make contact with anything she threw would probably improve if I just closed my eyes completely and swung at random.

If I understand IR correctly, and that is a huge assumption as I am brand new to fastpitch pitching, this illustration from the Journal seems to be IR,

Click to expand...

The illustration does not show IR.

Key points of IR:

* Ball is *pulled* around the circle.
* Hand is behind the ball at 12
* Hand is under the ball at 9
* The forearm pronates (internally rotates) during the release phase of the pitch.

The best video showing a complete IR pitch is this one:



Note also the brush interference...Amanda's arm makes contact with her hip at delivery.

A small quibble: Amanda does text book forearm pronation. She then does a "fakey" at the end to bring her arm into the HE position. Someone not familiar with IR might think this shows HE, but it does not.

(And, again thanks to Amanda for doing such a great set of videos.)

I think that although the forearm can rotate very quickly, it is not the key to the power of whip. IR and adduction of the upper arm/shoulder, combined with flexion at the elbow and upper arm pause are the keys to explosive acceleration of the ball from a lagged/loaded position through release. Watch for these in the following clips:

https://www.youtube.com/watch?v=XBoZ_KxQVUE
https://www.youtube.com/watch?v=u6z39S19x8o&t=11s
https://www.youtube.com/watch?v=vmiG4ji3onQ&t=12s
https://www.youtube.com/watch?v=k5X86nD_WS4

There is some forearm rotation which definitely contributes, as does the flexibility of the wrist, but I think that IR, lag/flexion (as a result of staying loose) and upper arm pause are the greatest contributors to whip.

sluggers said:

The illustration does not show IR.

* Hand is behind the ball at 12

Click to expand...

Based on the drawing on the JOSPT website, it looks like the back of the hand is facing 2B at 12 o'clock in Figure F.

sluggers said:

* Hand is under the ball at 9

Click to expand...

From figure H-it looks to me like the ball and palm are facing 3B, but I wonder if that is just the nature of the motion rendered in simple, rough lines.

sluggers said:

* The forearm pronates (internally rotates) during the release phase of the pitch.

Click to expand...

I don't know how to determine this from a simple line drawing.

Overall I was focusing on Figure F, with the arm at 12 o'clock.