With the head down as the horse eats, the neck and back are stretched out and open along each vertebra through the spinal column. This causes a very comfortable sensation to the horse because the spaces between each vertebra widen. This opening happens all the way from the connection at the head through the neck and back into the vertebrae of the tail.
With the head down we already know from a number of studies done on equine biomechanics and equine posture through the (ISELP) International Society on Equine Locomotor and Pathology that the muscles of the abdomen lift the horse’s barrel due to the mechanics of the nuchal ligament and superspinous ligaments. As stated by Gillian Higgins in her book How Your Horse Moves; Gillian stresses the vitality of the grazing position for the horse because it promotes correct posture which facilitates the correct use of muscles while working. Allowing the horse to have the majority of his day to graze is the ideal domestic life for the horse. However, it’s important to note that grazing alone does not provide the muscular development the horse needs for rider support. This is simply because the horse grazes in a static or very slow traveling walk making it unable to develop the muscles sufficiently over the back to carry the added weight of the rider correctly and maintain a healthy posture.