It is important to understand how your horse feels, therefore push down a finger on your tongue and try to run. You immediately realize that if your tongue can't elevate, you can't swallow, and therefore you can't run very far! This is how your horse feels with the constant pressure of a bit! Select a Myler Bit that relieves tongue pressure and allows more tongue relief and you may find you've removed your horse's reason to resist.
Dr. Joyce Harman (researcher about "Anatomy and Physiology of the Mouth as it Relates to Bits and horse comfort". First printed in the book "A Whole Bit Better by Ron, Dale and Bob Myler"), writes: if you have tension in the tongue, you have tension all the way down to the sternum and shoulder along the bottom of the neck, where you actually want relaxation. Properly bitting a horse for tongue relief can allow him to relax in the bit from nose to tail, regardless of the discipline or breed. Any horse can benefit tremendously from learning how to relax into the bit and collect into a natural, balanced frame.
As the Myler brothers investigated bit resistance, they were puzzled as to why resistance seemed to be worse with the bits that were most generally regarded as "kind": the singel-jointed or the three-piece bits. What they came to realize was that of the seven places (tongue, bars, poll, nose, lips, chin groove and hard palate) a bit can apply pressure, applying pressure to the tongue creates more evasion than all the otherd combined. Their conclusion; excessive tongue pressure is the source of most bit resistance, and the bits that caused the most tongue pressure are the "broken bits", the single-jointed and three-piece bits.