How bits work …
A bit works by causing pressure on various points on the horse’s mouth and/or head as the rider pulls on the reins. With the correct bit and adequate training and competent riding, the rider is able to communicate effectively with his much larger and stronger partner.
It is important to recognise that a horse’s tongue goes down his face, so if his head is on the vertical, the angle of pull from the bit to the rider’s hands will cause backward and downward pressure onto the horse’s tongue, NOT into the corners of the lips
Tongue Pressure .
As in the previous paragraph bits mostly work off a horse’s tongue, creating a backward and downward pressure into the tongue when you use your reins. Solid or unjointed bits can only act on the part of the tongue which sticks up above the top of the bars. Jointed bits can drive downwards into the centre of the tongue way past the level of the bars.
To see how this feels, put the tip of your finger onto the centre of your tongue and press down with just a little pressure. Now , walk around for a few minutes whilst still pressing on your tongue. Try to swallow. NOW imagine replacing your finger with a pound of cold steel and replacing the pressure with the full bodyweight of a rider standing in their stirrups and hauling on the reins !
The horse can resist the rider’s rein signals because he is trying to evade the pressure of the bit on his tongue so he can swallow . The usual approach to a resisting horse is to increase the severity of the bit, or to add gadgets such as flash nosebands or martingales. These do not solve the problem, but merely mask the symptoms, forcing the horse, through pain or immobility, to submit to the bit.
“The Myler approach is completely the opposite. Seeing the bit far more as a means of communication than a means of control, the Mylers advocate using the most comfortable bit possible, so that no restrictive gadgets are required to force the horse into the “correct” position. The horse’s tongue should be given as much release as is right for that particular animal at that particular stage in its training, and the most appropriately shaped bit selected to suit the mouth of each individual horse. The Mylers’ aim is to make the horse comfortable and accepting of its bit, so it can relax and concentrate on what its rider is asking it to do .”