The film was directed by Tim Miller, a fellow best known for his work on visual effects and for founding Blur Studios. They're the company behind some of the best CG cut scenes in games and movie title sequences in recent history so it should come as no suprise that the effects work in Deadpool is top notch. This video feature breaks down just how much of this iconic sequence used digital doubles and other tricks to get the shots that were needed. Without harming stunt guys.
This scene shares a lot of DNA with the sequence which was leaked a couple of years back and was directly responsible for pushing 20th Century Fox to go ahead and finally make the film. That video was created by Miller with some help from Ryan Reynolds and was an entirely CG affair. We also still don't know who leaked it, but there's a rumour it was one of the production team.