Do you ever feel like sometimes an answer is presented just when you were asking the question? It happened to me recently. It had come to my attention that I didn't appear to be explaining one of the techniques I use in teaching loose leash walking very well.
As I was pondering how I could improve my explanation and better help more students Denise Fenzi of Fenzi Dog Sports Academy noticed someone leading their young horse. She noticed that when the horse got excited and started pulling, the handler guided the horse into walking in a circle. Once the horse settled a bit, they carried on in the original direction. Denise wondered if this technique could have applications in teaching dogs to walk calmly on lead and started trying it with her dogs and other dogs. The reports back were encouraging - it seemed to help a lot of dogs walk better.
Why? One possibility is that some common loose leash walking methods such as "Be a Tree" and "Penalty Yards" involve stopping, or backing up when the dog pulls. It is possible that some dogs find this stop in motion frustrating, leading to more straining forwards. Walking in a circle still allows the dog to move, so those dogs that feel so full of beans that they need to move their bodies can still move.