08/27/2026
The Mouth Seal
Horses are obligate nose breathers. They can't pant like a dog or breathe in or out through the mouth at all. This is an important physiological fact to keep in mind. With regard to research about bits, just about all of the "bad things bits cause" occur only because of this physiology. The resulting take home message is, if you offend the tongue, they will try to withdraw the tongue, and a lot of unfortunate things then occur.
If we are aware of the mouth seal at all, chances are good that we are thinking of the lips. The lips are a part of the mouth seal, but arguably the lesser in importance. That research mentioned above and the ill effects bits can have deal with the other half of the mouth seal. In the back of the throat the soft palate and epiglottis keep the airway open and the esophagus (food tube) closed off.
When we do something to cause a defensive tongue withdrawal, the rear of the tongue bunches up and puts upward pressure on the seal formed by the soft palate and epiglottis. This is known as dorsal displacement of the soft palate and is why racehorses will sometimes be run with a tongue tie 🤮. When this happens, the airway changes from an interstate to a country road.
Fortunately, this problem is somewhat easy to avoid. If you understand the mouth seal in its entirety, and you simply don't offend the tongue, nothing bad happens. 🥱
A relaxed tongue also means the holy grail of positive physiology is still occurring while we ride. 👅 With a fully functioning mouth seal, and a tongue that isn't radiating tension through the hyoid apparatus to the rest of the body, a horse should still be swallowing while working. Swallowing is a major reflex and closely tied to the nervous system. If you shut down swallowing a sort of tension clock countdown has begun. ⏱️ Each time they swallow, tension is released and the clock resets.
On average, a horse swallows every few minutes. Did you know a horse typically produces 10-15 gallons of saliva a day? Not swallowing for 10 minutes is an eternity. Sit there for a bit and see how long you can stop yourself from swallowing before it gets pretty uncomfortable. ⏱️
Offend the tongue and you're kinda water boarding your horse. I'm not sure why he's hard to catch and bridle though...
When I began this bits and bitting undertaking one of the more helpful resources I found was a human speech pathologist who specialized in helping stroke victims learn to swallow again. We seriously underappreciate how imporant being able to swallow is.
The tongue is the only part of the body involved in 3 of the 5 senses (touch, taste, and smell). All mammals must suckle. Even puppies and kittens, born blind and deaf, use their mouths to explore and find mama's teat.
Keep worrying about ficticious and marginal stuff like the nutcracker effect and their bars though. You only get to the bars through the tongue... The most data collecting and communicative part of the horse, its tongue, is probably not worth studying... Just buy a new bit. That'll probably solve the issues. Ignore the fact that horses can only tie cherry stems into knots with their tongues since they totally lack opposable thumbs. Nothing to see here...
It just might be a good idea to start paying attention to your horse's swallowing. If you see it while you're actively riding, congratulations. Your horse has given you a gold star. 👩🎓 If you don't, ease up on those reins. You've got some work to do.
One last thing. There are at least a couple of my peers out there teaching that the mouth seal doesn't exist or isn't important. I'd just ask if any of you have ever used a straw with a little hole in the side? Does it work well? Horses drink from the ground level and have to suck water up about 3 feet before it goes down to the stomach. If you can figure out how to suck water up a 2" hose a distance of 3 feet with no kind of seal, I think NASA would like to talk with you. Just a thought, but you won't find research saying that horses have 4 legs either. Some anatomical/physiological things are taken as a given and nobody in the know would even consider they need to be proven.
