I have 3 horses my self, and one younger girls boards her 18 year old Arab there. She rides once a week or so and allows me to ride him as well. He lost a ton of top line over the winter, and is overall pretty green. His owner also needs quite a bit of help with her seat. Anybody have any good horse and/or rider exercises? Bonus points if they can be done in or include a round pen!

I would recommend lunging- may need to be done on a line for control reasons. Lots of trot work without someone on his back will help. He shouldn't just be moving around under saddle.

Also, walking/backing up and down hills to engage his hind end, and trotting poles/raised poles/cavalettis can help with that as well.

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These were all things we were advised to do with Zippy, and they've definitely helped- though his topline was in pretty good shape to begin with. I'm not as certain about rider seat, unless you have a specific example of what she's struggling with?

Trail ride! Go on different terrains, up and down hills, across streams, etc etc. Nothing better for developing topline and seat

Flat work in a surcingle and over poles

For the rider: trot/canter with no stirrups on the lunge.

I used the have a... questionable seat 😅

what my trainer always did was put me on bareback and we walked over poles, and worked up to trot, that can help a lot and it helped me a ton. If the horse is not comfortable barwback then try the exercise with a saddle but stirrupless

Neck and leg stretches for the horse, balance exercises (without or without an excercise ball) and/or yoga for the rider. Or make her ride blindfolded so she's more focused on how she's sitting/moving with the horse. And I mean supervised riding in a controlled environment XD

I would definitely recommend stirupless and/or bareback work along with balancing exercises on a lunge like having her sit tall and hold her arms out straight and into a circle motion. Another good thing is to have her lean back and picture the seat as if she's glued to it and being held down.

Riding without stirrups trotting and cantering on and off the lunge would help a lot. The first time I cantered without stirrups was off the lunge on a spicy horse lol.