long shanks, which I used to have for my racking horse, are for headset only not control. if your heavy handed a bit like that can cause alot of pain. its what gets that horse to hold the head high and in towards the chest, this causes a slight hollowing of the back which makes it easier for the horse to get into it's running walk.
when a horse lifts it's head like that they hollow the back, just think of the neck, and back as one piece because they are, what the head and neck does affects the back. in order for naturally gaited horses to do the rack, or running walk, shuffle or finos gaits they have to have a slightly hollow back to get their back legs slightly behind them to execute their gaits. it also causes the horse to put more weight on the back and takes some of it off the front legs so the horse can lift it's front legs in the distinctive way that is showy.
also if the rider leans back a little it hollows the back even more making the gait even faster and easier for the horse to do, as for racking or the fast running walk.
so it is headset only not control remember that. if that same tennessee walker or racking horse or saddlebred was ridden in a snaffle or small shank you would notice less of a upright tight headset. the head would be carried lower but still somewhat inward with the head towards the chest.
if the rider was heavy handed in those long shanks the poor horse would have his head in the sky and in your lap at the same time. we call that sky gazing.
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