One of the consequences of becoming a blue belt is that the higher belts have taken the kid gloves off another notch. It is really remarkable how much pressure a group of not very large people can deploy.
No doubt it can all be explained by force divided by area equals pascals. Plus, in absolute terms, big white belts have felt as heavy on occasion. What makes brown and black belts’ pressure notable is that it is unrelenting and casual.
Generally, whatever else they’re doing on top, they’re also pressuring in. Which rapidly becomes tiring and demoralising. It also requires you to devote a significant amount of attention to enduring or avoiding their pressure. And they never appear to be trying to apply it either by brute strength or even by specifically altering their positioning for that purpose. It’s all small effortless adjustments to the position that they’re already in and the movements leading to or comprising their attack. Which is itself demoralising.
This leads me onto one of those small insights. Part of the skill curve is about expanding the scope of things that you can do without thinking about them or at least with minimal attention. This is what allows you to do a lot of the more impressive stuff, because it frees the attention you need.
A low level example: it’s possible to defend an americana or kimura by keeping your arm almost straight (but not absolutely straight, because that allows for an armbar). This should buy you time to execute an escape. I’ve never made it work, because I can do the defence but it takes 80% of my concentration to maintain it. Leaving me no brain space for my escape.
Similarly, I suspect higher level grapplers are constantly making slight shifts from the bottom to redirect or counter top pressure, without really thinking about them. And, naturally, the top pressure itself is the result of a similar process.