It can be called Ground Driving, Long-Reining, or Long Lining. What it is, is basically driving a horse with two long lines while you are walking on the ground. Sort of like lunging, only with a second line. It's benefits are numerous! Long lining builds top-line muscles, and teaches softness in the bridle and self-carriage.
You can see ground driving depicted in old horse training manuscripts and artwork as it was sometimes used in classical training (or high school dressage, such as that practiced by the Spanish Riding School in Vienna, or the Cadre noir of Saumur in France).
One of the things I have noticed in long lining Atticus, is the ease with which I can ask for shoulder-in and half-pass along the fence line. As I am not always correctly balanced, and definitely stronger on one side than the other when it comes to using the proper aids, I frequently worry that I may be confusing him or inadvertently giving conflicting cues. I don't have to worry about this with the long lines.
Additionally, I find it's a great way to work on an issue that I would not be comfortable riding the horse through. Here is a short video of driving him away from "home" (the tacking / untacking spot) when he decided he was done working and the ditch made a handy excuse for him to refuse.
Whenever he tried to spin away from the ditch, I would turn him again to face it and encourage him to go forward. If he was at least facing the right direction, I would verbally encourage him. After a number of refusals, he realizes it's easier to go over than to continue refusing. It's the same principle under saddle... take the pressure off if the horse is doing the right thing (or even just THINKING the right thing, as in facing the ditch without backing or turning away).
I find that having this ability to reinforce your requests without danger works really well for under saddle behavior.
