One way to do this is to create a separate model with different weight painting, and then apply a force (with an empty object) in Blender.
Weight panting can be used to make an object jiggle like this.
https://www.youtube.com/watch?v=ZfAJeUYAv3MThe trick here is do what a stunt person would do; it only has to appear as a striking blow.
You can then decide how many frames you want the force object to operate in; usually 24 frames for a full second of strike.