Behavioral performances of our legged robots are still far behind those of biological systems. Energy efficiency and locomotion velocity of our robots, for example, are orders of magnitude lower than those of animals, and in order to fill the gap, it requires a radically new approach in the design and control processes. From this perspective, we have been exploring a novel approach to design and control of legged robots which makes use of free vibration of elastic curved beams. We found that this approach not only simplifies the design and manufacturing processes of locomotion robots, but also substantially improves their energy efficiency, which is comparable to those of animals. In this paper, we explain the novelty and principles of this approach through the four representative case studies that we have been exploring, and discuss challenges and perspectives toward the future. © 2012 IEEE.