I'm sorry, but this isn't a reply as much as it is an "I second that!"
I really really want to know what ideas people have to offer up about this -- i just signed in to LLLI to ask this very question. My 12mo daughter started trying to stand at 3mos and hasn't really let up, which is a problem for me while we nurse because I have neck and back problems (run over by the front and rear tires of a truck when I was 18mo that resulted in OA of the spine and a fused neck 10 years ago) and am very uncomfortable nursing unless we're lying down.
As my daughter gets older, taller and stronger, her trying to nurse while standing is becoming more and more of an issue because, while latched on, she'll transition from lying down to standing, to sticking her butt in the air, to twisting side to side and back down to lying. She also rapidly changes breasts, sometimes pulling off quite hard. Because she is so active, her latch quality suffers quite a bit and no amount of repositioning really helps because she never gets tired of the acrobatic routine. I've tried sitting up and cuddling her, but she aggressively resists being held still and ends up moving just as much.
I just don't know what to do …*after 11 months (the first month was an I-know-why-women-give-up-on-nursing experience that, fortunately, we lived through!) of beautiful tears-of-joy-and-wonder nursing, my nipples hurt all day long and I'm worried that we'll be unable to continue on to nurse until my daughter truly wants to wean (I'm hoping we'll make it to 18 mo at the very least …*2+ years, ideally).
I don't think I mentioned that my bundle of energy has 10 teeth, 5 on top and 4 on the bottom. She got her first two (bottom) teeth when she was 4.5 months old and I've never had any problems with uncomfortable nipples until the last week (even with the acrobatics, which have been going on for at least 6 months).