The 'holding down' is a form of the 'Alpha Roll' and should never be done to puppies or young dogs. It was developed by professional trainers to be used by professional trainers on severely aggressive dogs, after all alternative methods of training have been tried and failed. The 'Alpha Roll' would then be tried, only as a last attempt to save the dog from being PTS.
When it is used on younger dogs and puppies, it can have adverse effects and actually make them worse aggressors, or the opposite can occur and their spirits can be broken, and they end up being fearful, cowering, hiding under the bed messes, which then need to be retrained to begin trusting humans again.
I will say some members have gotten 'lucky' using this method, and I just want to say here that it was intended to be used only once. Repeated use will not improve matters and may cause the adverse reactions mentioned above, or worse.
From:
Alpha roll - Wikipedia, the free encyclopedia
Monks of New Skete, The (2002).
How To Be Your Dog's Best Friend. Little, Brown & Company.
ISBN 0-316-61000-3. "In the original edition of this book, we recommended a technique we termed "the alpha-wolf rollover"...
We no longer recommend this technique and strongly discourage its use to our clients.... The conditions in which it might be used effectively are simply too risky and demanding for the average dog owner; there are other ways of dealing with problem behavior that are much safer and, in the long run, just as effective."