Bruised butt from riding without stirrups! How can I fix that?

I think I might be doing something wrong, but when I trot without stirrups I often get a sore butt after. Today my instructor had me trotting a long time without stirrups, both posting and sitting, and with one stirrup or none. It was fine for the first few minutes of trotting, but soon it was painful each time I hit the saddle. I'm a relatively new rider (I've been riding for about 6 months, once a week) so I might just be doing something very wrong. It's not my muscles being sore, although they do get sore sometimes.
Any ideas on how to prevent this bruising? (It occurs where my butt bones are, not the tailbone but the two front ones) Also, do you have any tips on how to post properly without stirrups? Posting seems to make the pain worse when I don't have stirrups, and I often land on the pommel. And one last thing! How should I post the trot with one stirrup without tilting?
Thank you so much!

How do you fix it? By doing lots more riding with stirrups!

With practice you'll soon get your balance and stop bouncing around. Make sure you stay relaxed throughout your body and absorb the movement through your hips and lower back. Make sure you don't lean forward or hunch, or grip with your knees.

I'm guessing you're a girl - I found that when I was sitting the trot on very bouncy horses with a jackhammer trot I'd be a bit more comfortable if I wore a sanitary pad in my underwear. Less bruising, and I found it easier to relax knowing I wasn't going to be so darn sore!

If your butt is bruised, imagine how the horse's back feels! When sitting the trot you should not be bouncing or 'hitting the saddle' at all. You should stay in the saddle the entire time, moving with the horse's step. I know, it's easier said than done. Here are some tips:

Relax your hips, sit back and swing your hips with the motion. If done correctly you should be able to feel when each of the horse's front legs comes forwards. Also keep your back nice and supple. Instead of bouncing, absorb the motion by lengthening and shortening the small of your back (in other words, slouching slightly and then straightening your back with every bounce). Be careful not to overdo this. You should only be doing it as much as necessary to stay in sync with the horse. If done correctly, from a viewers standpoint this would look completely natural and smooth.

Good luck, hope that was helpful.

What are you riging - a close contact? A dressage? The twist may be too narrow for you, or the seat could be too broad or not configured right for your build. I had a lot of trouble find a cc with a moderate enough twist. HDR, Thornhill 24k, modern Crosby Pris des Nations with padded flap all work.

Dressage, I don't know. If I ever rode serious dressage, I would need a custom saddle.

Try riding without stirrups in an all-purpose saddle. Most of them have a wider twist. The Wintec AP (500 and 2000) and the more-streamlined Wintec 500 dressage that had a shallow seat are on the same tree. Their close contacts are too narrow twist for me, anc Collegiate cc and Bates cc use the same trees. Or just borrow somebody else's saddle that's a different model.

Bruised/sore seat bones are part of learning to ride properly. The best solution is just to endure the pain and keep going. It will fade soon (it will heal quicker the more you do it) and you'll be a better rider for it. Plus, if you ride through it, you won't get sore again. If you pad up or stop riding until you're healed, then you'll have to go through it all over again when you start back up.

Um, so what does it mean if we don't have a sore butt? Are we doing it wrong or is that just a saving grace of having a well padded posterior?

(I'm not joking)

LOL, I would guess it could be a combination of things; perhaps too much weight on the feet or squeezing too hard with the knees/thighs, thus eliminating the weight from the seat. Or some extra padding might help, I don't know.

I know that when I was having to take long breaks between instances of riding (months), I would always get sore when I came home and rode properly. If I rode wrong with all my weight on my feet (bad habit that I still struggle with sometimes) I wouldn't get sore.

Grr, must be the extra padding, in which case, maybe I'll never be sore! (gotta think optimistically, right? Lol)
I know it's not the leg thing because the BO was watching me and said that I impressed her by not doing that...I was confused at the time because she TOLD ME NOT TO squeeze with my legs so I didn't... heh

Anyway, thanks for the answer, learning and improving is definitely a process.

I've never had bruised seat bones....

It sounds to me like you are gripping where you shouldn't... maybe with your knees or sitting too far back with your legs too far infront so your weight isn't distributed in your seat.

ANY gripping/tenseness will cause you to pop up like a spring. You need to learn to siiinnnkkk down into the movements.

Actually I have to disagree. If you're thumping hard enough in the saddle that your seat bones get bruised and sore, it's a sign that you are being WAY too hard on the horse's back. No horse should ever have to endure that, as it will wreck their backs and teach them to hollow out. Having a bruised butt is by far not an essential factor in learning to ride.

While not too much weight should be put in the legs (meaning no bracing, pinching with the knees, or gripping) there should be a natural flow of weight down into the legs that helps with staying balanced and not bouncing. Also the motion of the horse should be absorbed in the back, hips, and abdomen as well as the heels and legs. So, if riding correctly, you do not have to endure bruised seat bones.