The positive effect of walking on creative thinking (2014)
fermatslibrary.com
fermatslibrary.com
From personal experience, I recommend an elderly dog as a companion to keep your pace down. My very good boy is named as co-author on a couple of recent patents.
The brain is amazing. Quirky, but amazing.
I think the reason is simple: our bodies and minds set themselves in a kind of low-power mode when we're sitting or lying down.
This is why we have to drink so much coffee or other stimulants to do useful work while sitting.