Well it had to happen sometime. Im in this video.

Fajin or the explosive use of power is practiced (after a few years of training the moves slowly) and is necessary from time to time to help remind the body the actual speed of the martial application as well as to test that you are standing right, not overreaching etc. It is very easy if you do the moves for a one time slowly to get into bad habits very gradually and have poor posture, resetting with the faster moves helps to expose those weaknesses. We always warm up a lot before doing those moves or you can hurt yourself.

Should also look up the spear form, which is also done quite quickly.