1. Your fine motor skills will be gone.
2. You won't able to access the knife bearing arm easily
3. Any technique that is based on smooth arm deflection and or manipulation has very little chance of working....unless you're disarming a zombie.
Next major problem.....Jacobson has the bad guy in the video standing with knife hand forward and easily seen. The reality of a knife attack is that you won't see the blade before the attack is launched. When you look at knife attacks that have been caught on camera you will see that 80 plus percent of the time the free hand is out front to grab, punch, pull and distract then FOLLOWED by stabs or slashes from the knife hand. The free hand in front makes getting control of the knife hand extremely more difficult.
Next problem Jacobsons bad guy is stationary, not moving. In every surveillance video I have watched of a knife attack the bad guy was moving forward....ALWAYS.......You will be likely moving backwards, your balance will be compromised, and you'll probably fall to the ground. Jacobson spends a good part of the video talking about getting to the inside off the knife or closing the gap. The problem here is that the bad guy initiates the attack he is moving in toward you. He has a knife you are unarmed he is reaching out to grab you to stab you in a sewing machine type attack. He is already within arms length...He has closed that gap for you whether you want him too or not. The reality of a knife attack is that you will have very little time and space or distance to react and deploy a counter-attack or strategy. Its more than likely that you probably won't be able to stop the first stab(s).You probably won't have time to draw your own weapon (gun, knife, pepper spray, etc); at least not before being stabbed a couple of times.
Nothing in Jacobson's Reality knife defense videos is even relatable to or realistic even if the bad guy is using a knife as just intimidation......he hasn't stabbed you but just wants to rob you. Bad guys generally want one of three things;
1. your property (money, jewelry, etc)
2. your body, (hurt or rape you.)
3. your life, (they want to kill you.)
Even in these scenarios the knife isn't seen until it's too late. So the same principles that a knife attacker uses still applies even when he is only threatening with it. The robber leads with the free hand to hit, grab, pull distract or punch. In other words they don't hold the knife out from 5 feet away and go "give me your money". The knife is hidden until the moment of the attack. They normally grab you and have the knife at your throat. There is nothing in any of Jacobson's knife defense vids that resemble an actual violent encounter with a knife.
Jacobson is obviously impressed with her techniques. Too bad that none of the shit in this vid would work. This short vid not only has the same problems as mentioned before but using this vid as another example lets address why the stuff in this vid wont work.
The assumption that you're a super martial artist/superhero/badass/ninja and that everything you do is going to work perfectly is and will be your downfall.
1. Time - We never have enough time. Fights are generally over by the time you realize what's even happened. We never have the time we think we have to react or do something like what Jacobson demos in her vid. In a dojo we always have time to get ready, we have time to get in a ready position or defensive or offensive state, take a stance etc. Also in the dojo things are slowed down to make the technique work. In reality the luxury of having "time" is something one doesnt have in the street. The attack comes quickly, so whatever response you decide to do has to be able to operate within a very small time frame.
2. Space - There is no real space in a fight we normally don't have the room to operate or to pull off techniques. The Space to be able to do your techniques is very seldom afforded to us in a attack. Having someone at arms length or the proper range is a luxury at best. The reactionary gap closes in the blink of an eye. Our attacker will not be stationary or cooperative. The bad guy initiates the attack he will be going like fuck at you. There IS a constant aggressive pressure from the "bad guy" he isn't try trying to establish a "sparring range".or looking to take it to the next round.
3. Effectiveness - Our "shots" may not be as effective as we want them to be. People think well if I just hit them a certain place or a certain way with enough force it will be over. This, like the first two, is just a stupid assumption. Most everyone who was stabbed in a street fight didn't realize they had been stabbed until after the fight was over. In other words they continued to fight despite being stabbed several times. There have been people who have been shot several times and continued to fight. So unless you been able to render the bad guy unconcious right off the bat there is still a chance you will get hurt. Like it or not people, even the bad guys continue to fight regardless of being hurt or injured.
Things to consider for a second, you don't see martial arts moves being pulled off effectively or even at all in violent encounters in the street. The few times we do see martial arts in the street is usually in a street fight and its consentual. But that even begs to differ. How is it that a person with no training can get the best of a martial artist, who has trained for years, in the street? Jacobson's knife defense videos are prime examples of exactly what not to do and serve as a testimonial for her lack of any knowledge of the reality of violence in today's society.
Jacobson's knife stuff and other vids like it should be taken down its not only irresponsible, it's negligent. Her self devised tactics won't work, been proven not to and will get someone killed....it's criminal. If one of her student ends up getting killed trying to defend themselves using those tactics then Jacobson should be tried and held accountable for their murder much as the guy with the knife.