I ride English (I am English), so I know what you mean. How about the following, which you should be able to do in the comfort of your own home:

For your thighs: Use any rubber or plastic ball as long as it is at least a foot in diameter. Sit on a hard chair that allows your knees to sit at right angles to the floor. Shuffle to the edge of the chair so that your thighs are completely off of it, and place the beach ball between your knees. Squeeze the ball between your knees, hold for fifteen seconds, and then release. Do this a few times a day until 15 becomes easy, then increase to 20, then 30, and so on. Apparently this is a great way to increase your ability to hang on to your horse with your thighs. It increases the inner thigh muscles.

How about sit-ups for your core muscles. No apparatus needed. Don't over-do it initially though, it hurts lol

For calf muscles, how about this: stand on the stair closest to the ground, holding onto the rail at first and balance on only the balls of your feet. Slowly stretch down and lower your heels until you feel the stretch in your calves. Sound familiar? This is recreating the stirrup! Hold for ten seconds. This should not only improve your position, but your balance as well! When you're ready, try letting go of the rail until you can balance for two seconds, then try five, then increase little by little as you improve.

Best of luck!

When fitting for up for timber racing I see riders spending ALOT of time in 2 point at all gaits. If you are eventing, I would do a lot of hand gallops too. I think in your situation exercise on the horse is what I would do.

Here is what I am thinking ...you know how a biker can be in great shape, for biking, but can't swim or run? There are muscle specific to your sport. I am not sure of your discipline.

I went from somebody who occasionally rode "western" once a week to somebody who takes 1-2 English lessons a week and rides my aunt's horse English/western/bareback whenever I can scrape up any other free time. So I've really been able to follow to progression my body has made. For me one of the best things is to pick up a trot (English) and work from going between medium posting trot to two-point to sitting trot. Maybe throwing in some attempts at lengthening trot and collected trot. This is was my trainer has us do for our "warm up". When your muscles feel like they're giving out at posting trot go to a two-point and so on. the idea is to keep doing this until you can go around the arena many times and not be struggling. The other thing I find that helps a lot is bareback. Now your horse may or may not be up to this. My horse (aunt's) doesn't like bareback and puts up a little fuss at first but I've learned how to snap her out of that and mostly she's fine unless I have a balance check or something. I figure the discomfort comes from my seat bones hitting her wrong. So I recently bought a comfort plus bareback pad to try to make her more comfortable/ less Annoyed. I'm of the opinion some horses do awesome bareback and some shouldn't be ridden that way. But it depends on your horse. But nothing will help your balance and position more than this IMO. I can't imagine home exercises being anywhere as helpful as actual saddle time (or lack thereof). Lol but I also know how hard it is to get to the barn most days. -alyssa