Originally Posted by NBEventer
When I teach sitting trot the thing I find works is a very old school technique actually. I tell the student to think about dropping all their weight in their seat bones like their bum weighs a thousand pounds and think of their ankles absorbing the impact. Then to open up their pelvis and almost pretend they are peddling a bike backwards. It seems to work well. When my students learn sitting trot I actually encourage them to lean back until they feel like they are leaning to far. The reason is I find as soon as someone starts sitting trot they want to pitch their entire body forward and go into fetal position. So if they think of leaning back with their shoulders square, their pelvis open and seat bones weighing a thousand pounds it seems to work.
Now I do not throw this all at them in one sentence. We do each individual step first. So they start by thinking of sinking their weight in their seat bones. We do a bit of trot, if they don't get it then I say think of peddling a bike backwards while sitting deep. Sometimes this works. Then I tell them to think of leaning back. And just keep building it from their. They almost always seem to get it by the time I have them picture peddling backwards.
I take reins away when learning sitting trot as it is when they seem to want to balance on the reins the most.
Before Health & safety kicked in they used to have bareback trotting races at gymkhanas and leaning back was the way to go if you wanted to win.
Obviously you have to know a correct seat position but if that involves perching on top of a horse afraid to move a muscle, bones so tight they'd snap if someone moved them then you'll only ever be a passenger.
I like your description of 'the heavy bum', I try to think of myself sort of melting into the horse, you develop a deep seat then you feel every movement and even though you're relaxed you're actually totally prepared for every move they make so if they do spook sideways or leap forwards you're still sitting in the saddle and with them and not hitting the ground where they once were