Is the nutcracker effect a myth?

[gracelyn4]

This might be asking for trouble, but I am genuinely interested in learning.

The “nutcracker effect” is a term widely used to say that a single jointed bit will poke the top of a horse’s mouth when you pull on the reins. Or at least that’s how I see it used quite frequently.

However, I’ve heard some people say that this is a myth and that a properly fitted single jointed bit will not hit the top of a horse’s mouth. (I believe there was a study floating around where they x-rayed a horse’s mouth to prove this) But most online resources and even trainers and professionals use the term.

So I’m curious. Does anyone who has actually studied the issue, not just heard it said by others, know if the nutcracker effect is real or not? And if it is: is it an issue that will always arise in a single-jointed bit or is it more of a very rare exception?

[MHM]

I think it depends on the horse.

After the vet told me one horse had a low palate and I switched to a bit with two joints in it, I noticed a big difference in his behavior. It was immediate and permanent with the new bit.

[Christa_P]

I agree, it depends on the horse. Mine have generally been comfortable in a single joint Dee or Eggbutt. I ride with a loose or no noseband so it would be obvious if they didn’t like it, but they have quiet mouths and take contact without a problem. My current horse (OTTB) actually gets fussier and less steady in a double joint bit, of course she also requires the right size - 4 1/2" thank you.

[Posting_Trot]

I think that the nutcracker effect is distinct from the possibility of the bit hitting the roof of the mouth.

The nutcracker effect is the idea that when the rider pulls back on both reins with a single-jointed bit, the bit arms collapse onto the bars and compress and “crunch” the lower jaw.So the bit is the nutcracker and the lower jaw is the nut.

Poking the horse in the roof of the mouth is a separate problem.

[before_color]

@MHM

I think it depends on the horse.

I agree. Their personality and the anatomy of their mouth dictate what bit works best, I’ve found.

[agadorsbits]

Yes, at least in the way that most people interpret it. A nutcracker directs all forces inward, so the idea that a bit must press up into the palate is incorrect. This could only happen if there were a force pulling the bit up from below, which would require pulling the reins directly downward. The “Nutcracker Effect” can’t occur without intentionally causing the bit to push upward. Instead, the bit compresses the sides of the tongue, depending on how much it can close around the mouth.

See x-rays in the article here:

Bitting_The_Inside_Story.pdf

“When tension was applied to the reins, the mouthpiece pressed more deeply into the tongue, thereby causing the joint to move away from the palate. Single-jointed bits are usually described as having a nutcracker-like action, the implication being that when tension is applied to the reins, the angle between the arms of the mouthpiece closes and the joint is pushed toward the palate. In our study, any nutcracker effect that tended to push the joint toward the palate was more than offset by indentation of the tongue.”

That said, we are not disputing that bits don’t hit the palate in general (many do including double broken), but that’s typically a mouthpiece thickness issue rather than single vs. double joint.

Many horses do, however, strongly prefer double broken snaffles, but that could very well be explained as a preference of less bar pressure or the bit design itself (too many pressure points, too thin, thick for the horse etc.).

[Ghazzu]

Clayton did some investigating of bit action.

A fluoroscopic study of the position and action of different bits in the horse’s mouth
.
.
A fluoroscopic study of the position and action of the jointed snaffle bit in the horse’s mouth