It's official--a study at my alma mater, Stanford University, showed that walking is a way to increase your creativity.
Great writers have known this all along, of course:
"Me thinks that the moment my legs begin to move my thoughts begin to flow." - Henry David Thoreau
Charles Dickens walked about 20 miles a day, partly to relieve the stress of writing, and the people and places he observered often inspired the content of his novels.
Aristotle taught his students while strolling with them (which led to them being called 'peripatetics').
The Stanford study showed that creativity increased while walking and for a short time afterward. It didn't matter whether the walking took place inside or outside. In one experiment, the walkers had twice as many creative ideas as people sitting down.
However, walking was not better for the kind of thinking in which you search for one correct answer (in fact, it was mildly worse for that).
But for generating ideas, start walking!
more on the study: http://news.stanford.edu/news/2014/april/walking-vs-sitting-042414.html