Hey,

I just saw this post... sorry for being so late... here's a cool tutorial that goes deep into rigging. The section you particularly want is on the third page, in the section titled "Constraining the Torso to the Feet."

I put the link to the beginning of the tutorial (first of three pages), because everything was really good...

https://www.peachpit.com/articles/article.asp?p=102022

-- From the book, _Maya Character Skeleton Setup_ by By Chris Maraffi.