A news item for you. Theoretical research on walking, running, and the transition from one to the other. Nothing directly useful here for awhile, but if/when this gets better developed, it means that a legged robot can stably walk and run without needing a lot of sensors and fine control over the real time position of each moving part. Instead the mechanical design of the leg, plus fairly simple control over the angle that the leg meets the ground gives good control. Major reduction in sensors, feedback, and needed processing power.
The article also includes a link to a link, that would allow buying the full 6 page Physical Review Article.