I think you're confusing the terms "pressure" and "pressure testing".
In jiu-jitsu, pressure is a concept (and sometimes a submission) where you simply use your weight to make the other person suffer. Pressure is usually applied through knee-on-belly (exactly what it sounds like) or various pinning positions where you get into side control or mount. Kesa gatame is a prime example:
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However,
pressure testing is something completely different. Pressure testing often has little to do with "pressure" as a force, but rather the philosophical pressure of "does it work live?"
An example of pressure testing is: I can nail a scissor sweep during the drilling/technique portion of class. But can I hit it when we get to live rolls? If I can, can I hit it on people that it actually means something to hit it on?
- Maybe it only works for me in drills. My pressure testing is that it doesn't work.
- Maybe it only works for me against white belts that are smaller than me. So I can make it work, but is that the bar?
- Maybe I can make it work on white or blue belts up to my weight class. As a purple belt, that's still not good enough for me.
- Maybe I can hit it on any white belt at will, most blue belts with proper setup (except for that one guy who weighs 375 pounds), I've hit it on several purple belts, and while I haven't finished the sweep on a brown or black belt, I've at least knocked them over and used the ensuing scramble to improve my position.
- Maybe I can even hit it on brown and black belts at will.
The concept of
pressure, as a method of inflicting gravity on another person, is mostly absent from the idea of
pressure testing, the idea of increasing resistance to your technique until you've hit the point of failure. Maybe "resistance testing" would be a better term for it.