I don’t understand Japanese particularly well, but I can nonetheless recommend this video of a Japanese TV show segment on juko-kai practitioners (Americans, by the way) demonstrating their combat ki by getting punched in the throat, kicked in the ribs, and kicked someplace else (even more delicate) — first by what look like American football players, then by Japanese (lightweight) puro resu fighter Genki Sudo (or Sudo Genki, in Japanese).