I suspect it's a mental context switch more than anything physiological.
For example, I'm pretty bad at creative tasks when at a keyboard (this was also true in pre-internet times, so it's not a matter of distractions), but sit me down with a pencil and paper and the juices start to flow. It just creates a different state of mind.
Re:Things I've quit doing at my desk
by icebraining on Sunday September 16, 2012 @03:49PM
(#4530133)
For me, often just looking out of the window (we have a nice view on our office) helps a lot.
I combine both by walking near a blackboard.
I tried to replace pencil & paper with minimalist emacs buffer but .. paper is non linear, just like thought trails so it's a better fit for now.
Re:Things I've quit doing at my desk
by politician on Sunday September 16, 2012 @10:08PM
(#4531067)
There actually is something to the idea of getting blood flowing to the different parts of your brain -- there's also a study showing a correlation between the nostril you're currently breathing out of right now and which nervous system is dominant (you have two). There's a breathing meditation exercise where you try to alternate nostrils -- it's a bit trippy once all of that O2 starts hitting both sides of your head at once.
My theory about thinking and walking is that it gets the blood flowing round the brain more than just sitting at a desk does. I think that was the thinking behind having table tennis tables in offices as well, to get the blood moving around. There's also something about the action of walking that seems to let the mind wander off as well though...