I got a sad call from a new client recently. She said her dog was showing signs of dog-dog aggression and, from the advice of someone in the dog park, she hired a trainer that uses choke chains. She said initially the training wasn't too physical, but she ended up firing him because of his increasingly abusive techniques when dogs were around her dog.

She noticed that since those sessions, her dog has gotten worse, and more anxious when dogs come into view. I was not surprised and told her that is one of my main reasons for never recommending physical, or fear-based training.

From a learning perspective this is what can happen and probably happened in this case:

Just remember, dogs react to things that they are afraid of. If you use physical methods, you might get your dog to not bark, but the anxiety will still be there.