In the training class with Massad Ayoob, I am impressed with just what a Pioneer he has been.  He will use a phrase that he coined back in the 80’s…. And I couldn’t tell you how many times I’ve heard it since by other trainers. To help his lectures, he will show old videos… No one before him was talking about this stuff… And everyone since has taken from it.  
It was Mas that did the pioneering work on what happens when one is in a stress situation…. He actually put science behind it.  I studied his book when I was a much younger and faster person, and I have heard all this since from others… But its all stuff that Mas pioneered first.   A very remarkable man. 
I’d dare say that Massad Ayoob is right up there with Jeff Cooper in Trainer Icons.