From the archive
Robots Learn to Push Heavy Objects With Their Bodies, Just Like You
The payload of a robot is a well-defined number that usually refers to how much mass its actuators or mobility system can comfortably support. The payload of a human works in a similar way, except that sometimes we can cheat, by offloading the mass of an object to the ground, and moving it purely by overcoming friction and shoving it along.
Discussion
Next, we need to teach them to apply balm (or may be grease) to their joints after finishing work :-p
I am sure robots are already capable of that (they are just not telling us)