Join Date: Dec 2010
Location: southern Arizona
I don't think leaning back, or rolling all the way onto the back pockets is what folks are suggesting. Just sitting here on a chair, if I feel my pelvis and keep my back straight, my lower back is pretty rigid. If I unlock my lower back, my pelvis rotates about to the lower edge of my rear pockets. That is about the position at which the western instructor I took lessons from this summer stopped saying "Get on your pockets!"
One of my biggest problems in riding is my tendency to lean FORWARD. Not slouch forward, but roll forward on my hips and lock my lower back. I then am rigid as a post, and will bounce and flail all over the place. Rocking here on my chair, I'd guess about 10 deg forward is enough to lock everything.
My natural sitting position, back vertical, still locks my lower back. If I don't move my shoulders back, but relax my lower back, my shoulders shift down maybe 1/2" - hard to tell without a mirror. It isn't a slouch, because my back doesn't go round. And it doesn't shift my rear much, although it feels more like I'm on my pockets.
I think that is what most western riders refer to as 'on the pockets'. It isn't leaning back, and it isn't looking like a sack of potatoes dumped on the saddle. I wish I knew how to describe it better. For me, "Unlock your lower back!" might be more accurate than "Roll onto your pockets!" - but the effect is the same as what got my instructor to stop shouting at me this summer.