I've been reading over the past six months about the finer points of using the leg yield - or not using it, as the case may be - and when several blogs I read had leg yielding info this morning, I decided to look for something that concisely addresses the controversy over the movement, which many classical dressage riders feel should never have been put into the first level tests in the United States.
A quick Google search found an article that does a great job looking at the leg yield and outlining its benefits and its disadvantages - GO HERE TO READ.
You'll need to scroll down to get to the article itself, and once you've read that one, there just happens to be another article below it about the older rider - written by a dressage rider who is also an MD. Interesting material and recommendations for those of us "riders of a certain age." :)
Over the past few years I have gradually stopped using leg yield when riding Keil Bay. He much prefers shoulder-in as a suppling exercise and the immediate benefits are glaringly apparent in whatever exercise we move on to in that ride. I get the best canters from him when we do shoulder-in first, and I also sometimes use shoulder-in as a "go-to" exercise if he is being spooky towards any particular part of the arena or any object - especially if the object is known to him.
With Cody (although it's been ages since I rode him - daughter keeps him working well!) I used to do spiraling circles using the leg yield, which seems to balance him and get him using his hind end in a more engaged way. However, the last time I watched daughter do spiraling circles on him, I made a note that it's beyond time to teach him shoulder-in (I'm actually not sure if he's ever done it or not) and see what the benefits are for him. There are only so many spiraling circles one can do in a given ride, and that exercise is not one I'd drill over and over again.
I'd love to hear folks' thoughts on the leg yield, and what your experiences are using it, or if you don't use it, what you do instead that works well.