Scot E. Dowd Ph.D.  Encyclopedia of the APBT (Click here to read about the author)

Backcrossing as we might remember from the discussion on Breeding is when Outcrossed dogs are bred back into one of the original bloodlines (see Outcrossing). While we may not see the degree of heterosis that we might see in the original outcross we should maintain a level of this vigour in specific individuals. Here is where selection and luck are vital. Less that honest appraisal of the F2 outcrosses backcross can lead to reestablishment of traits we were trying to breed out or traits we are trying to avoid. Thus, it is this F2 or highbred individual that is the actual goal of the parental outcross and backcrossing functions.
 
NOTE: Usually Outcrossing is done in pairs with closely related linbred individuals which allow mixing of the backcrossed progeny which would hopefully set the traits we were attempting to bring into our bloodline with the outcrossing. A double backcross (taking an outcross back into the original line F1 and the progeny F2 from this also back into the original line again (double backing). will typically reduce the original influence of the outcross such that we are virtually back to linebred status. What we would instead try to do is perform two logical outcrosses and two backcrosses and then interbreed both outcrosses. As stated the goal of Outcrossing and backcrossing is to set traits without severely increasing the Inbreeding Coefficient?.