The Healing Arts that the Nia Technique draws from are: Yoga, Feldenkreis, and the Alexander Technique. Helen Terry (black belt and Nia trainer) gives brief explanations of some of the qualities that Nia extracts from each of these healing arts. For information about the other 6 movement arts that contribute to Nia, check this video

For more info about Nia's foundational arts, check out the definitive resource, The Nia Technique.