About the Videos
Cutting an object is generally a simple enough task, given the correct tool for the job. A sharp knife is very useful for everyday cutting chores, which is why this particular tool was created, carried, and utilized by mankind for the last several thousand years. Some force is necessary for cutting, of course. A sharp knife requires the use of less force to do a particular cut than does a dull one. If one is cutting something quickly, and wishes to inflict the maximum depth and length possible in that cut, then the use of more power and force might be helpful. In combat, things happen quickly, conditions are not ideal, and targets move around a lot. A cut as performed in a cutting demonstration may not be practical when used in a combative environment. Many of the power cuts used in cutting demonstrations put a person far too out of balance or twisted away from the object they were cutting to be useful against an opponent who may strike back at you.
In simple terms, as the blade moves through the target, good cutting technique involves keeping as much of the edge of the blade you are using in contact with the target to be cut as possible while the edge is pressed into and slid along and through the target with sufficient force to accomplish the cut. Again, in simple terms, the more edge that is drawn across a particular spot and the more force that is used to draw that edge across the spot, the deeper the cut will be at that spot. Of course, in the real world, targets move, have different consistencies, some are more difficult to cut, the shape and the edge geometry of the blade can affect the cut, and other factors can come into play. However, from a basic technique standpoint, hitting the target with as much of the edge as possible while applying significant force is a good model for cutting technique.
In order to draw (or push) as much of the edge as possible across the target, the joints of your arm must be mobile. Doing a hacking or cutting motion with your shoulder tight and your wrist locked will result in sporadic edge contact. Cutting with a tight elbow and/or shoulder also saps speed. Speed is necessary in combat to make sure that your target does not move out of range while you perform your cutting motion. Speed also helps in the development of power to complete the cut. The energy used to perform the cut is going to be kinetic energy, or energy derived from motion. The formula for determining kinetic energy is = x mass x velocity squared. If we are talking about cutting with a particular knife during a short duration of time, the mass is not likely to change (absent the loss of part of the knife through breakage). Similarly, in a short amount of time, the mass of your arm is unlikely to change (even if you ate a couple of dozen donuts prior to starting the cutting drill). To increase the kinetic energy, we need to increase the speed of the motion or increase the mass of the tool (get a heavier knife). Now, all you physicists out there, I do realize that I am not discussing many of the other variables that can exist. I realize that this is a very simplistic model of a complex activity. The simple model should suffice for our purposes. In order to hit the target before it moves and in order to have the maximum energy to perform the work of the cut, we need to have a speedy cut, using my simplistic model.
Please review the video and note the difference in body posture when the two-dimensional, stiff-jointed cutting is conducted versus the fluidity of the motion when the wrist, elbow, and shoulder joints are allowed to bend and three-dimensional rotation and cutting occurs. Please note that stabbing, coring, hacking, scraping, push cutting, and other uses of the blade are not covered in this demonstration. The principles displayed in this video do apply to these motions. However, the draw cut or pull cut motion that is displayed was chosen for demonstration purposes because it is a very common cut and allows for a clear and concise demonstration of cutting technique and application.
Thank you for your time. I hope you found the video beneficial.
Tuhan Holloway, July, 2008