Legged robots with arms can potentially replace humans in dangerous and dirty tasks, where vehicles with wheels and tracks cannot go. Some possible application domains are: disaster recovery (such as cleaning-up the Fukushima nuclear power plant), search and rescue, forestry and construction. Traditionally quadrupeds have been limited to load carrying or observation tasks as they have no manipulation ability. To remove this limitation, arms can be added to the body of the robot, enabling manipulation and providing assistance to the robot during body stabilization. The arm system will add a new dexterous manipulation capability to the already wide range of abilities of the HyQ robot, e.g., trotting, running, jumping, stabilization, external disturbance rejection, quick reflex action, and careful foot hold planning during navigation through unstructured terrain. This enables HyQ to perform new tasks, including: removing obstacles, grasping and manipulating objects, opening doors, or assisting the robot's balance.