CrossFit ILC - Why shoulder and elbow pain from kipping pull-ups
Channel: 아무데서나 운동하다: Workout Anywhere
Date: 2014-06-14

It's related to bent wrists while swinging. Plus, it is not about pulling the bar, but about pushing the bar and maintaining that pushing-generating tension all the time whether you are ascending or descending. 

Even if it takes much time and a lot of efforts to increase the explosiveness from you core, stick with it, not pulling through your wrists, forearms or elbows, "core to extremities." It is worth it since ultimately you will find yourself "doing something common uncommonly well," like Coach Glassman has pointed out.