Originally Posted by HorsesAreMyPassion
Also remember that your elbows should feel loose and elastic, not locked and stiff. In rising trot your elbow should open and close as you rise up and down. If your elbows are locked your hands will go up and down as you rise and sit. Your hands should stay in place and your elbows should open and close like a hinge.
This! This! This!
I SO struggle with this. My instructor pointed out with me that I do not have a soft enough elbow and when I put some focus on it, the horse felt different and moved better. How little it takes to come off as "locked" in the elbow. In fact, the elbow is where a lot of the give and take happens. A rider might kind of "freesze" her elbow for a sec in a half halt or other transition. It really helps to think of your elbow as being connected to your physical core and that through the elbow to hand to bit, you recycle the horse's energy back through your core to it's hind end.
Charles Dekunfy talks a lot about the elbow defining the seat to the horse. Not something I fully understand , though.