On a recent discussion forum the topic was, using chain leashes for dogs that bite the leash when they become aroused by environmental changes (seeing another dog). How about teaching a dog not to bite the leash, PERIOD. Biting a chain leash will not keep a dog who is over threshold from biting a leash. Biting chain leashes cause broken teeth, that is a fact.
Train the dog to leave the leash using clicker training methods before exposing him to environmental changes that puts him over threshold. The rules of Tug of War and keeping the dog under threshold apply in the case of the exuberant Lab (as seen on the show: "It's me or the Dog".)
Rule # 1 Drop it and leave it must taught
Rule # 2 Only tug when I ask you to.
Rule # 3 Only tug on toys I want you to tug on.
Rule # 4 Dog needs to be kept under threshold and desensitizing to other dogs before going out for a real walk.
I was a bit disappointed that Victoria used a shortcut to teach the owners how to train their dog. But live goes on and dog dentist need to make a living, too.