Basically, they hold the flap of skin on the nose out (like a breathe right strip for humans) to decrease airway resistance and may possibly help improve performance. They may also apparently help with bleeders, as this is thought to be related to airway resistance. No evidence as yet to prove their worth, however David Marlin has suggested their possible uses in his book (Equine Ex Phys) and the lecture I went to recently. A bit of a "tried but not tested" as yet. I got a free one at the lecture, and I'm planning on trying it out if my horse starts bleeding after hard work again (although it's not exactly flawless research lol!)
D'you know, I thought you were going to say that.....
Well, I reckon it's not going to have any effect on bleeders.
As for whether it has any effect. When a horse starts to exercise or even anticipates excise a physiological reaction dilates the nares. Horses have had 50 million years to get this right so I wonder whether we are likely to be able to improve on it with some sort of strip? Interesting.
Probably not, but if it makes the owner/rider feel better, surely it's having some effect (if not even on the horse)?! lol! I know I do a few things that probably don't benefit my horse, but make me feel better!