I've been told the same thing with bits and that they interfere with the horse's breathing. However I heard that from a Myler DVD and not from Dr. Cook.
Since horses can't physically breath through their mouths, the only way it can do so is the fact that there is something in a horse's mouth which is probably hard for it to swallow, as many know. But I still can't see how that interferes with breathing. Until somebody, not Dr. Cook, tells me scientifically how a horse can't breath well with a bit I will continue to think that its just a way for a person to sell their product.
Like bsms has previously stated, some horses do better in bits than in a bitless bridle. If I'm correct, isn't your Arabian calmer in a bit than a bitless bridle? All horses are different, like different things, etc.
I've ridden my filly in a bitless bridle, halter, Myler (level 1 snaffle), and all of these other things. She rides the same, nothing changed. So frankly, I don't see the point in changing from bit to bitless. To be, a bit is just for asking a horse to get supple, soft, and collected and not for control. I will continue to ride my filly in a bit as when I show, but if I just did trail riding then I would pop in a bitless bridle. Simply because, like I've stated before, bits to me are for suppleness and collection. I don't think I can get my horse collected well in a bitless bridle, but if I did just trail riding then it wouldn't really matter, as long as she's soft in the bitless I'll be fine with it.
The fact that Nevzorov keeps his horses isolated just tells me that he has NO CLUE about horses and their natural ways. He claims that he is natural and that he trains from the soul.
Because this is what happens with you 'train from the soul'. Horses don't train through the soul, they alpha of the heard trains others through his/her body language. And if she has to bite them, then so be it the horse has to move out of the way. I feel that Nevzorov just thinks that training horses is like flying around with a magical wand and not to be the alpha in the relationship because 'I want to be one with the horse.' Again, very unnatural. There is no such thing as 'being one' in the world of horses. Your either the leader or your one below your horse, which is what I think of this guy. There even is a video of his horse biting him, actually I've seen a couple of his horses biting him.
The fact that he doesn't teach his students anything when he works with horses just suggest that he has some black magic going on in that stable. If he truly wanted to help the horses he would be putting up all of his videos and teaching each and every person on how to handle their horses the way he does. And like a previous poster has said, that's very selfish.
He's a guy off his rocker. No wonder why he doesn't ride his horses anymore. Maybe because one of his horses bucked him off and bonked him in the head a bit more and thought, "Oh dear, I'm getting a message hall horses must not like being ridden!!"