No stirrups is the way to go. If you do it correctly, your legs will be in a perfect position and 10x stronger. I force myself to do no stirrups all of November and march to keep myself in shape
Hey Makia, I asked something like this a few weeks ago! :) Some users told me to swim, run or making squats, not only work in our horse riding lessons. :) I hope it helps! <3
Look for previous questions, because they are some like this with great advices.
No stirrups! Not only will it strengthen your legs, but it will give you a better seat.