Problems with Blum's Karate Article

[makamo66]

I have a couple of concerns with Haywood Blum's article "Physics and the art of kicking and punching." First of all, Blum considers a beam with a couple applied to the ends of the bar when he should be considering some kind of mass impacting the bar in the center and second of all, why does he use a beam and not a flat plate? Also, he doesn't take into consideration that wood is orthotropic and simply uses the formulas for an isotropic material. Unfortunately I couldn't find a free PDF of this article online any more but I was able to download the PDF at some time before.

 

[jedishrfu]

I searched for a free online resource, and sadly, there is none to review. This makes commenting on it somewhat challenging.

I found an article on the art of punching, but it doesn't cover actually striking a target. However, it may be of interest for other topics:

https://www.thescienceofstriking.com/training/the-biomechanics-of-a-knockout-punch/

 

[webplodder]

I have a couple of concerns with Haywood Blum's article "Physics and the art of kicking and punching." First of all, Blum considers a beam with a couple applied to the ends of the bar when he should be considering some kind of mass impacting the bar in the center and second of all, why does he use a beam and not a flat plate? Also, he doesn't take into consideration that wood is orthotropic and simply uses the formulas for an isotropic material. Unfortunately I couldn't find a free PDF of this article online any more but I was able to download the PDF at some time before.

Well, those points do make sense. An impact test would indeed better model a punch or a kick. And yes, wood isn't exactly the same in every direction, so isotropic assumption there is rough. But maybe Blum was just simplifying, trying to make a quick point. Beam does give clearer bending moment... though a plate might've been closer to the real shin or the forearm. Do you think he missed out the injury part altogether?

 

[jedishrfu]

The original poster (OP) hasn't been back to PF since summer of 2025. In addition, we didn’t have the article to even discuss the OP’s critique.

@webplodder thank you for your comments. Yes, it could well be true that the article was simplifying things. However, without access to the article it's difficult to say.

In any event, since this is an old and dormant thread, I think it's a good time to close it.