What is being shown in this video, all be it very well, is a simple demonstration of structure. Now the fellow demonstrating it, Chen Xiaowang is clearly very physically able, and is very practiced at this method of body use. I wouldn't say that the average person could do what he's doing without a significant amount of training, probably around a year or two. However the principle that he is using in this demonstration can be achieved by any average person in only a few minutes, and you can show a similar feat against someone significantly larger than you as soon as you understand what I am about to write.
When the strong man pushes into Chen Xiaowang, Chen locks his arm under strongman's arm pit, joining their structures. Every time the strongman pushes he is actually pushing against himself via a very simple redirection done by Chen Xiaowang. Here is a diagram to help you understand this principle.
Because of the simple redirection, every time the strongman pushes (force "A"), that force goes through Chen Xiaowang's structure, and back into the strongman (force "AB"), pushing the strongman up and back, and Xiaowang's structure down every time he pushes.
This is not to say that it is easy to redirect this much force, but it is possible, requiring you to use much much less force than the pusher is using. This is a simple example of mechanical advantage. You should try it with your friends, you'll be surprised!
Here is a clip I made a year or two back, explaining the same thing:
Here is the whole video if your interested in my views on structure and alignment: