I am having trouble keeping my legs from swinging forward during a posting trot, this also happens when I start a circle. I know I do it but have a difficult time keeping my legs underneath me? Any suggestions?
Practice more and more. Part of it is finding the right technique, and part of it is just building the muscles. Keep your heels down but don't try to push up with your feet. Remember your knees are the "hinge", that's where the movement is, and your thighs are the muscle. Think of it while you're riding.
I have this problem with my new students and I have found lunging the person on the horse without reins has worked beautifully. They can balance themselves by holding onto the mane but never the saddle. This help with finding balance and their center and also building confidence. Practicing posting and 2-point and transitioning from the posting trot to the 2-point. Without having to guide the horse and worry about the reins gives them more concentration on their legs. I see great improvement in their legs the 1st time we try this and they can feel the difference. My students love it and feel empowered.
When I ride, I grip with my thighs but also post off of my legs not my feet so much. Heals down is important but without the grip of the legs, the lower leg just falls forward. It takes practice to build up the leg muscles to keep the leg in place. Post without stirrups. Great excercise. Good luck
Try keeping your heels down and try to keep them with the horses side and grip the saddle with your thighs. I used to help with trails at times at a ranch and I was told to lead them at a canter Which by the way I have never done and I pushed my heels down as far as possible and tried to stay deep into my saddle and my feet never budged!! I was amazed! They would just stay against the horses sides,