Oh, I meant to add to explain my comment on lunging being counter productive: the chriopractor guy told me to lunge 1 hour 3-4 times a week....IMO, that's just too much. The horse would get so bored, I think, that he'd get pissy about doing it. Granted you could make them do it, but heck it bores me, why should they enjoy doing it, or even tolerate doing it. IMO, it's just better not to get that sort of thing started. I think it would be better for them to get their exercise from riding.
Boredom is NOT good for horses....creates horrible, bad, and lots of problems:\
Becky
I think the other counter productive effect from that much lunging is that it's too much turning. Even if you change direction and speed frequently, all that circling is hard on the joints. What you do, lots of trail, is the best regular exercise a horse can get.