Animation preview model global orientation

Hello,

I'm total noob when it comes to models, animations or Unity assets in general so don't assume that I know some obvious 101 stuff because I probably don't.

I have created a human jogging animation in MotionBuilder based on some mocap data. It is natural that data is imperfect - not exactly running in straight line etc. I have however looped the animation so that all of the bones and joints transformation (except z axis) and rotation are identical. In short the model ends the animation exactly where it started (except z axis) and in same pose. I would expect model with that animation to run in straight line and so it does in MotionBuilder. It is no longer the case after importing to Unity.

When I preview the animation in Unity there is this thing:



I assume it represents some kind of global model orientation. I looked through documentation but nowhere does it say about this gadget what it is, and where it comes from exactly.
The red arrow is aligned correctly with the grid (character facing forward) in first and last frame. However it wobbles on frames in between. As a result my character does not jog in straight line.

Can someone explain what does this gadget in picture correspond to exactly?

 

I found it to be present in documentation after all:
http://docs.unity3d.com/Documentation/Manual/RootMotion.html