Things that did not work for me:
-soften your elbows.
-think of your arm as a rubber band.
-shoulders back.
-touch your shoulder blades together.
Things that DID work for me:
-upper arms by your sides.
-then “pushing” my hands forward did work because as the horse gestures it’s head (walk and canter) my hands go forward a little, then return to “upper arms by my sides” as the home base.
-a riding crop held on top of my hands, under my thumbs so that my thumbs stay on top; trying to do so without a crop just made my whole arm stiff. The crop allowed my hands to develop muscle memory while I focused on the rest of my arm.
-strong shoulder rather than shoulders back; total game changer.
I discovered pushing my hands forward by myself. I always thought of softness as being my hands come back as the neck gestures up. When really it’s much more pushing forward as they gesture down, then passively come back to neutral as they gesture up.
I agree with the counter top exercise listed above for the trot. The trot has always been an easy one for my elbows as I just visualize keeping my hands in one place, so my elbows must pivot as I post.