Yes, that's true - but the practicalities of modern life mean that most people have to use a lead to get to an exercise area, and the old adage is "never train a wired dog, only train a tired dog".
I want to let my dogs run and get rid of some energy so that they are in the best possible frame of mind before I train them;
Errrm sorry but why would you want to get rid of a dogs energy before you train 
I would have thought that you should be able to train a dog with this high energy, as well as after it has let off some energy
Surely if you only ever train after they have let off some energy you ain't gonna be able to control / train them if and when needed when they are full of energy
I train ALL my dogs both when they are full of energy and after they have let some out - as this was the advice I got of a fantastic well known trainer (before I had cockers, and also since I have had cockers)
Wow - thats impressive
I would stand absolutely no chance of training Dax at the moment when he is highly excited
I admire you if you have managed to get your dogs to listen when they are full of energy - but then Dax is only a baby and he is doing fine so far
My philosophy is not to set him up to make mistakes and when he is distracted he makes mistakes
he is learning fast and I'll stick at it - lots of hard work to come but it will be well worth it
I was interested in the comment on harnesses and conformation
having changed over from a collar to a harness I'm a bit worried that this could damage his conformation
it seems that whatever I use could result in damage when Dax pulls - working on avoiding this but it is quite difficult at times so I am going to get the bungee lead and hope this will help
