- Apr 17, 2019
- 335
- 63
You asked if the arm was more a whip or a catapult. Just saying that if I have to choose between emulating the action of a whip and the action of a catapult for acceleration, I'm gonna pick the whip. The analogy isn't perfect, but if an 8ft bullwhip can take your arm input and accelerate it to mach1, I'm interested. I don't think you were suggesting that a straight arm like a catapult is the most effective way to accelerate an object, but I don't think muscling the arm during the throw is efficient. Accelerate the arm rapidly, compress it against the body to stop it. Let the ball eject itself, don't need to force it.What does the sound barrier have to do with anything here?
I concede that the tension pulls the sling portion straight. It's more the linkages and transfer of energy between the segments that is interesting. And the arm doesn't just have just one linkage, we have linkages all the way down the shoulder, elbow, wrist and knuckles. A whip has basically infinite linkages. Which is why I like referencing their physics.The sling on top of a trebuchet is not a whip, it stays perfectly straight during the throw.
I think my point in sharing is I find it very interesting that it was pointed out in both videos that the transfer of energy is initiated by the stop (whether the hand or the weight).
Agreed, but lag and BI are two different things. There's lag when you throw overhand but no BI.
You would have a better argument if you equated the BI to the pivot point in a catapult or trebuchet.
I think there's two concepts that get conflated on this site, as someone in this thread said BI for 'control and improved velocity'. Those are two distinct things in my head, maybe I'm not on the same page as others, interested in feedback -
- Brush Interference of the forearm against the hip/thigh for release point control. Same reason that if you're setting a glass of water down on a coaster without looking at it you're probably going to use your pinky/hand to touch the coaster to spatially orient yourself. If I practiced this often enough, I could probably reliably set that glass down without the reference, but would still be more reliable if I oriented myself.
- Compression of the upper arm against the ribcage to stop the arm and initiate transfer of momentum (a la whip or trebuchet) for velocity.
I believe this action is necessarily different from the overhand throw (extension toward the target vs tight to the body), but that's probably for another thread.
I also teach BI of the forearm for control, but less for finding the release point so much as a reference for the position of the hand and arm when it gets to the release point - keeping the arm tight to the body and teaching which part of the forearm brushes to indicate I/R is happening at the right time. If they lose the BI as they get older and have good I/R, I may not sweat it so long as accuracy isn't impacted (hasn't happened yet). As soon as a student says they're having trouble with accuracy my first thought is let's look at the consistency of release, and BI is a part of that.