Nine Dragon Trident form from Choy Lay Fut kung fu.
Also, when practicing internal martial arts, one of the key characteristics is moving the body from the core. The foundation of moving from the core is the pelvis area.
Michael Buhr, the author of the Internal Gong Fu blog has written an eBook on working the pelvis to improve one's martial arts practice. There is a huge amount of information available for a very low price. It is available for the Kindle. Please check it out.