Len Sclafini on Punching Rotation

The following is gleaned from the American Journal of Physics, Vol. 43, No. 10, October, 1975. The article is entitled "Karate strikes," by Jearl D. Walker, Physics Dept., Cleveland State University

The two parenthetical statements are mine. I added them for context and because I'm not quoting all previous text. So, just so you're not totally lost, here is brief synopsis of pertinent information from the article, so you know from whence the numbers come.

Stroboscopic data tells us that the maximum velocity of about 7 m/sec occur at about 75% extension of the arm. The punch takes about 0.2 sec to deliver. Miller and Nelson in their book "Biomechanics of Sport" say that for a typical 70 kg person, their arm mass is about 10% of total body mass.

If you are not punching anything, and there is no deformation to the fist, then the maximum energy available to deform your opponent is 156 Joules.

The units are not important; just keep the number (156) in mind for purposes of reference.

Walker writes:

"Introductory karate students often believe that the rotation of the fist in the forward punch described (above) significantly adds to the energy delivered to the opponent. If we treat the arm as a solid, uniform cylinder (for simplicity) of radius r = 3 cm and use the arm mass (M) and punching time (w) from above we find that rotational energy Er is:

Er = M X (r^2) X (w^2) / 4 = 0.4 Joules

which negligible compared to the 156 J calculated before. Similarly negligible results are obtained for punches in those styles of karate in which the fist is rotated immediately before contact rather than continuously throughout the punch. So, fist rotation appears to be largely for the most comfortable use of the arm muscles."

Personally, I don't buy his last sentence, but I included it for completion. I think it is more opinion of his part and naturally that can be argued until we're all dead and the next generation of CD'ers have this same discussion.

Anyway, that's the black and white of it. The laws of mechanics have withstood the test of time. Not even karate is beyond their jurisdiction, although many seem to think what we do is the exception.

Len