Fajin explained @taichi

In this short clip, I’m giving a brief explanation about how to do Tai Chi Fajin. Many people do it with explosives, I focus on the connection. The whole body unites at the finish to maximize the power created by movement and mass. The legs push, body turns and arms extend. Qi expands and spirits expresses.

Update: After seeing some responses, let me clarify.
I didn't mean other martial arts don't follow through when striking. For power, everything, including sports follow through for power. Throw a ball or throw a punch, they are similar. I've alway said there are more similarities than differences in Tai Chi and other martial arts. 
What I was referring to in the video is when a person punches bags a lot, there is resistance that's like hitting back at your body. Professional fighters have more support from trainers and others to keep their body balanced. For most people, in time, it's hard on the body. For that reason, it's better to work on other techniques.