You would think I would have learned this before now given how long I have been riding (rode for the first time at 3 years old. Had my own horse at 7, sweet black and white paint named Suncloud), but it took riding with Leslie to help me truly, fully, understand how to control a horse almost exclusively with my seat and my core muscles.
I can go from an extended canter to a canter so collected we’re almost cantering in place just by using those core muscles and thinking more up than forward. I went from a trot into some of the best piaffe and passage I’ve ever had — again just using my core muscles while keeping my leg relaxed by gently pulsing.
The rein is just softening and making the horse more supple with gentle movements of the wrists and fingers.
I also had Vento backing without any pressure on the reins. Just moving the bit gently in his mouth and using those core muscles to say, move, but my hands are saying, but not forward. He was so light and had his hindquarters tucked neatly beneath him which is what you want in a proper rein back.