A way that can help keep your lower legs in place is riding and jumping without stirrups. I do this about once a week to keep my legs strong. It makes you learn how to grip with your whole leg and not just your knee and thigh. It also gives you a lot of balance and trust in your horse. Right now I compete in jumpers where its basically all speed and turning and I have a lot of balance on my horse from riding without stirrups.
It is not just a horse,
It is the one thing that keeps me from being just a girl