The last cold steel "proof" dvd I got was carefully contrived to give the impression that knives are somehow like lightsabers. A minor flick and body parts start dropping off. Lots of meat. Problem is that it was meat that had been removed from the bone and there was no skin or clothing on it and it was slashed at vertically - the direction it couldn't move. Another demo had carrots in a leather glove attached to a wooden dowel. Slashes started dropping carrots off. The point was supposed to be that your fingers would drop off if they got hit with a knife. Two problems: 1) fingers aren't carrots and 2) hands-wrists-arms aren't rigid.
It doesn't take that much to do your own experiment. Next time you are cutting up a chicken or a turkey, do a slash and see how deep it goes. Hang a turkey leg from a string and take a swipe at it with a tactical folder and see what it does. Next, buy an old shirt from the thrift store and take some of the material and wrap it around the turkey leg and try slashing at it again. I guarantee you it won't be nearly as impressive as the cold steel videos are. I still wouldn't volunteer to let someone slash at my arm, but fingers don't drop off with a single snap cut.
If you want to test the finger in glove hypothesis, again, not hard, take some chicken wings and stuff them into the glove, tie the glove shut and hang it from a string and take swipes at it. Again, I guarantee you not as impressive as the cold steel demos are.
The last problem I have with the cold steel demos is the careful way that Lynn Thompson prepares each knife cut. Lots of breathing and practicing even on the video. Knife cuts in fights are chaotic affairs, not careful execution style sword cuts. If you really want to test the effect of knives in fights, don't over prepare your cuts - do quick snappy cuts with little or no preparation at all kinds of angles.
All this is not to denigrate the quality of cold steel products. They are high quality knives and I own several. What the "proof" videos show is how sharp they are under controlled circumstances such that different knives can be compared. What they don't show is the actual effect of knives in combat.
