Boston Dynamics' BigDog may have already been replaced by the beefier LS3, but that doesn't mean it's totally obsolete. Today the company unveiled a version of the quadruped equipped with an arm where a head (or tail) would go. As can be seen in the following video, it's powerful enough to lift and toss a heavy cinder block.
Key to this work, funded by the U.S. Army Research Laboratory, is that BigDog uses the dynamic forces of its whole body to help it throw the cinder block. It begins by taking several steps to the side before quickly accelerating as it swings its arm, temporarily launching itself into the air in the process. This approach is similar to the way an athlete winds up before throwing a discus, for example, and greatly enhances the robot's throwing power. Since few robots are as capable as BigDog when it comes to balance, it's an excellent platform to test these sorts of strenuous actions.
It's somewhat puzzling that BigDog's new configuration doesn't include two arms, which is a form factor that has been explored by researchers in the past. Back in the early 1990s, the Japanese government unveiled a nuclear plant inspection robot with a humanoid upper-body that walked on four legs. The idea was to combine the stability of a four-legged robot with the manipulation capabilities of a human. More recently, a team at the Italian Institute of Technology has shown plans that would add a pair of arms to their quadruped HyQ, presumably for the same reasons.