The hyoid apparatus, is a delicate structure, suspended from the temporal bone at the base of the skull, and has a direct muscular connection between the mouth and hind legs; it is an important aspect in the ability of the horse to breathe.
The sternohyoideus muscle and the sternothyroideus muscle attaches the tongue and mouth to the chest of the horse.
This connection continues through the pectoral muscles, abdominal muscles and up into the pelvis. The Omohyoideous muscle links the fascial chain running from the head to the toe of the hindlimb.
The occiputohyoid muscle connects the poll to the hyoid apparatus. It creates a direct connection from the shoulder through to the poll, from the nuchal ligament and the dorsal muscle back to the hindquarter.
A restrictive bit causes limited tongue movement; therefore causing pain and tension in all the related muscle groups. This small, seemingly insignificant bone inside the jaw has an enormous effect on the syncronicity of the body as a whole.