A few weeks ago I posted a thread about Asa, a 7 month old female black Field Lab that is in our play group. Asa is an alpha, whenever there are other dogs around she wants to play fight with the other dogs to the point where the other dogs bite her to make it stop. If there is another dog close to her age she will jump on them and continue to bite them even though the other dog has submitted.
The solution has been to take Asa to a dog park where she plays with adult dogs. We were there for two hours this morning without incident. When she encountered a dog that was a stranger to her that was bigger she immediately sat down. According to Stanley Coren in "How to Speak Dog," this behavior means, "Although I am not subserviant to you I am not a threat to you." I'm not sure if this has anything to do with it, but Asa was spade about a month ago.