The brain then sends a signal for the foot to react, but the amount of time it will take for the foot to move will be the same as normal since the signal takes the same time to reach the foot. I imagine at 30000x, you would notice that it's taking very very long for the foot to move. To notice it would mean to have feedback from the skin inside your socks/pants that the foot/leg is moving against your sock/pants, and the brain will probably think that feedback is taking forever after it sent the signal.
Edit: I think this is the study we're thinking of. http://psychologyrich.blogspot.com/2011/04/does-bungee-jump-...
They couldn't see the flickering screen any better even though their subjective experience of the duration was longer.
https://journals.plos.org/plosone/article?id=10.1371/journal...
I don’t know how I got the opposite idea from the show I was watching. They were doing the experiment and I swear they said the people could see the numbers better. Perhaps if I had been bungee jumping while watching the show…
Fascinatingly, it seems that it is the perception of time that increases and with it the recording of information.
https://www.npr.org/transcripts/129112147
ABUMRAD: In that instant, our memories go wide open.
Mr. EAGLEMAN: Because thats what memory is for. Its for when everything hits the fan. You want to write it down and remember it.
ABUMRAD: So all of it goes right to your hard drive - the clouds, the feeling of the air. Oh look, theres a guy in a blue shirt.
Mr. EAGLEMAN: So when you read that back out, the experience feels like it must have taken a very long time.
KRULWICH: Hmmm.
Mr. EAGLEMAN: It must have.
KRULWICH: Normally, the trivial stuff gets dumped but in this situation, it gets written.
ABUMRAD: And then you realize how much trivial stuff is in there.
If it matters to communicate outside, sure. But if you're inside a synthworld with everyone at the same timebase, it's not a problem. Essentially, you're evolving 30,000x faster, so with enough minds in the synthworld, interesting things will happen...