How can I create Body Displacement/Physical Animations?

I'm wondering how to displace the body as it's done in the video below, i'm assuming it has something to do with Inverse Kinematics, but i'm unsure on where to start in the attempt to manipulate upper limbs to displace when an object with mass intervenes.

https://www.youtube.com/watch?v=ouILpk7dflE&feature=youtu.be&t=217 (4:23/4:55)

The person says they may release this soon (though they are apparently grounded), but i'm in a bit of a time crunch and want to figure it out and start now myself.