How was the author's productivity doubled? Where is the proof? How long has this been evaluated? Was it more than one day and a few strolls? It's already known

How was the author's productivity doubled? Where is the proof? How long has this been evaluated? Was it more than one day and a few strolls? It's already known that the brain is a "muscle" and thus needs rest to function properly. What I'd like to see from the author is more about why hourly rests might more positively benefit the brain than some other interval, and why. Otherwise, most of this is pure speculation!