I have ran barrels for years. And I run my horses in a D-bit, no tie down or spurs. And I am consistently 2-D. I have never had a lame horse. But they are fitted to it. And I agree.... when I do slow work starting the pattern on a horse... Ill do it 3 days a week. And trail rdie the rest. Once I start asking speed... the horses knows the pattern well enough that I don't need to work it but a couple times a month. And you can practice your turns and such on trails... pretend a tree is a barrel. That way your horse is still working the muscles needed.... but its not going to blow him over and make him a nut job because its not everyday on the barrels run, run, run. I also work cattle on my barrel horse and compete in many jackpots in Fl... and have won. So the more you do with him.... the more sound his mind will stay. My barrel horse gets ran at shows... that's it... I will do figure 8s and such at home... but I don't need to run the barrels. As he has a good, calm, solid foundation.
But if your horse doesnt and they are not fitted you can lame a horse for life. And if all you do is run run run... your going to end up with a nut.