Wow, I guess I know a little more than I thought. I said almost the same thing the two of you said. I wrote this answer right before I posted this thread here.

My dog love to fetch. However, he also likes to hunt for his toys. Perhaps you could hide some of her favorites in a big area. You could have her on a long leash. She would get lots of exercise and it would stimulate her brain, as well. Thus making it not just exercise. I can't think of what it's called but how about the course where they jump through a tire, go through tubes, etc. That might help. Don't know if you're wanting to get that involved in that, though. You might be able to construct some of that in your yard. I'll post just what you wrote on my pet site and see what they come up with, too. I'll send you the link when I get some answers. There's lots of very experienced people there.