Myth - Alpha Roll
Old dog training methods recommend that to teach your dog who is the boss, you should force him over on his back so that his belly is exposed. This is based on the myth that the Alpha wolf physically turns subordinates over to show that he is the most powerful and deserves to be pack leader. In fact, if you watch videos of wolves or observe a mother dog who is correcting her puppy, you will see the subordinate canine roll himself on his back exposing his most vulnerable side in deference to his superior. This is a show of respect freely given.
If we try to force a puppy over on his back, we can certainly do it if he is submissive by nature.
But with a confident and assertive puppy, you will have a struggle and that struggle will prove to the puppy that conflicts are won by force and the strongest and biggest wins. This does not create respect but could very well initiate fear in the puppy. Sometimes it might even lead to the defensive behaviour of making the first strike if the puppy perceives an imminent threat.