The first result of that effort was TrotBot's heel linkage. As you can see in the diagram below, TrotBot's heel strikes before the main foot, taking the weight while pushing backward to continue driving the robot forward. The resulting smoother gait reduces both torque and power requirements (for an analogy of why bumpy gaits require more power, think how much harder it is to do lunges than it is to simply walk).
Another benefit of TrotBot's heel is it steps higher on the backside of the foot-path, allowing TrotBot's rear legs to step about as high as the front legs to avoid getting stuck astride obstacles, as can be seen in this heel-path simulation:
Without its heel, TrotBot's rear legs probably would have gotten stuck on some of these 2x4s:
We've also played around with a few ideas for active toes that push down on the ground as the foot begins to lift: