There have been numerous studies that have associated walking a comfortable pace with better thinking. Numerous famous writers and intellectuals have remarked on the close relationship between walking and working through ideas. Among them, Henry David Thoreau (the author of Walden) and Daniel Kahnamen (the author of Thinking Fast and Slow).
If you’re stuck on an idea, and perhaps even if you’re not stuck - go for a walk!
Note: for benefits in thinking - only walk at a comfortable pace. Once you start to enter into Zone 2 you’ll have have worse results.