The liver, however, is especially vulnerable. It's the largest internal organ, about 3 pounds, sits in the abdomen, facing an opponent, and is slightly exposed under the ribs. Strangely, it takes a second or two, but when the liver is struck hard enough the body WILL go down and not simply from the debilitating pain. It simply can't help itself. Here's why:
The reason for the (body) collapse is, when your blood pressure’s going down, your body tries to instinctively control the blood pressure, and if it can’t raise the heart rate or restrict the blood vessels, it puts the body in a supine position so that it can maintain some blood flow to the brain. Because if you lose blood pressure to the brain, obviously it’s not compatible with life.
If you have a great disparity in size between characters, a blow to the right side of the abdomen will bring the larger opponent down 100% of the time. However, be certain the severity of the strike matches the size of the opponent. Larger bodies have more muscle and fat. You have to be certain you account for the greater mass. Also, if you make that larger fighter a lefty the scenario will be more plausible as a fighter who engages with his right shoulder forward puts the liver front and center. (Remember, the power hand is always back.)
I've attached three videos. The first is Bas Rutten's liver shot (punch). Bas is a legend in MMA, a member of the UFC Hall of Fame and a warrior for Christ. If you love fighting and you don't know Bas, you should. Bas isn't the one teaching in the video for some reason, but know the technique is his! And, you do need to know how to do it because it is not simply a strike to the side. Most of that is protected by the ribs. You have to make contact with the abs just below the ribs which is pretty darn tricky.
So, go back and take another look at that fight scene. Be sure the liver is available and not covered by armor, mail or the ilk. Get in close, strike fast, strike hard, and upwardly precise. Give the recipient a moment or two, then let the debilitating pain hit and drop them to the ground in a crescent shaped heap. Rest assured, the giver of said present will have time to escape, dispatch or simply stand back and enjoy the moment like a "Bas". (I LOVE that guy!)
Until the next round at FightWrite.net, get blood on your pages!