Cowboy Dressage Education
How tongue movement affects stride length.
It is well understood that a licking action of the tongue is indicative of increased relaxation in the horse.
In contrast, horses will often retract the tongue when stressed, or to avoid pain in the mouth from dental issues, a sharp bit, over flexion, a tight noseband, or other equipment such as tie downs, side reins and running reins. The horse might also retract the tongue when experiencing pain in other areas, such as from an ill fitting saddle.

The omohyoid muscle attaches to the tongue via the hyoid apparatus at one end and attaches to the horses shoulder at the other end. When this muscle is contracted in order to retract the tongue, it also affects the horses shoulder, blocking free forward movement and reducing stride length.