Of course all this is based on the following premise...
Horses bear weight on their backs better with a rounded (arched back)
rather than a hollowed back. I wonder if there have been any
scientifically based studies to prove this?
Head position purely from a static point of view cannot be terribly
important. It moves up and down (and consequently fore and aft) to
balance CG shifts due to the legs, movement in terms of overall CG shift
of the horse is small (no more than an inch or so) and cannot effect the
weight distribution to the legs a great deal (even dynamically). However
what can affect the weight distribution to the legs a great deal
(effective cg shift of more than a foot) is the stride of the horse. If
you move all four legs forward the back legs will carry more weight.
Also bear in mind that the vertebrae in the neck of a horse is about a
third of the way from the front or bottom-line of the neck and attaches
to the chest, there's mucho muscle on top of the skeleton here, so the
pivot point is a lot lower than a layman might think. So even though the
poll may be level with the withers the head is still "up" from the point
of view of the inclination of the neck vertebrae.
I've often wondered whether the rounding (arching of the back) is more
important than engaging the hind quarters (i.e. hind quarters engagement
and weight bearing is merely consequential), since the anatomy is
designed more like a wheel barrow than a shopping cart. Our efforts make
the back legs carry more weight but it is the front legs that are
designed to do this and the rears appear to be there for propulsion.
In any case it seems much more difficult to get real engagement, bend
and rounding than move the head around to a particular position.
I babble therefore I am!
Nicco
-- Open the pod bay door please Hal.