No way. I'm not a secret service agent, but I know presidents do not receive self-defense training. Presidents are surrounded by some of the best-trained armed guards in the history of the planet 24 hours a day, 7 days a week--the notion that they would need to get a knife out of an attacker's hand themselves is craziness. There are just SO MANY people surrounding them literally every second of the day.

That said, presidents (usually while they are still candidates) are given primers on how to behave and move in crowds to minimize risk, and they are briefed on what the Secret Service will do with them in the event of an attack (in most situations, I would assume that includes "us grabbing you by your belt and whatever else provides a good grip and throwing you forcefully into a car"). I've heard that a few presidents (Clinton, especially) regularly did not take the "minimize risk" advice, which I have to assume cheesed his detail off a bit.