Abstract: How does a robot’s body affect what it can do? This talk explores this question with respect to a morphology common to biology but rare in robotics: the presence of a bendable back. Using the Canid and Inu quadrupedal robots, I describe and quantify several advantages afforded by this morphological design choice for legged machines that can be evaluated against the spine’s added weight and complexity. Additionally, I discuss control strategies related to quadrupedal running with a spine.