There is that scene where Kaladin takes a sharp turn at high speeds and he almost blacks out. That is normal for jet pilots, since they experience high G forces when their airplane tries to accelerate them by their backs and bottoms.
But Lashing doesn't work that way, it generates fake gravity. Accelerating your whole body shouldn't cause you anything, you can't even feel it.
Is this something that is an admitted physics hiccup or I misunderstood this kind of Investiture usage?
This one is actually in the process of flux, as I do more research on the effects of acceleration (including interviews with fighter pilots, which has been fun.) Basically, I realized I needed to beef up my understanding of all this, and then make some decisions on exactly how this all works, because I've been relying on instinct too much in some of these sequences.
So...that's a RAFO, I'm afraid. More because I'm still tweaking some of the little details of how I want this all to work. (In ways that become increasingly relevant as I look forward toward things like Windrunners in space.)
There are a ton of details to consider, even if I eventually hand-wave some of it with the magic. (For example, the heart pumping blood in a high-g environment. How does that interact, if at all, with stormlight? And the direct oxygenation of the brain implied by not needing to breathe while holding stormlight...)
We have several very large math-ish projects going on behind the scenes.
I think it depends on if lashing independently impacts each atom within your body simultaneously, or if it is only a subset.
There's one important fact you're not considering, but which is vital: reader expectation.
One of the questions I have to ask myself is this: What will the reader expect to happen? How will they expect to feel? Granted, none of us have ever flown like this before--but we generally imagine similar things, similar feelings.
As a writer, one thing I need to balance is when I go against reader expectations and when I don't. Going against the expectations can be interesting, but often takes a large burden of words and explanation to keep reminding them something is not how they'd imagine it to be.
For example, it took a relatively large amount of reader attention (and explanation) to keep reminding people in Mistborn that plants weren't green and the sky wasn't blue. In many ways, making something new (like a chull) is easier on readers than making something familiar into something strange (like the horses in Dragonsteel, which were smaller than Earth horses--and kept causing confusion problems in my alpha readers.)
As annoying as this example can me, this is why Lucas had sound, fire, gravity, etc in space. Starships banking in formation felt real to the viewers, even if it didn't make sense in context. I hope to not go that far, but these questions are something in my mind.
I try to be careful not to remove the sensations of magic, in order to keep the movements of characters grounded. Windrunning has left me having to decide how far I want to go with things like this, in order to preserve the visceral feelings for the reader.