What is interesting about this research is that, unlike in many psychological papers, the effect sizes are relatively large. That means that this research may actually have some practical consequences.
Although the authors do not report effect sizes directly it seems that, in many cases, walking shifted the distribution at least one standard deviation in a direction of higher creativity (that is a lot).
At the same time I wish the results were reported better, in many cases they do not even report the mean and standard deviation of different experimental groups.