> Anyway, when I ride for a long period of time (4 or 5 hours) she will
> get something that resembles big welts on her back in the saddle pad
> area. They are usually around the back part of the pad. They don't
> seem to be painful but they just seem to crop up.
>
> What causes this and what can I do to prevent it??
You are experiencing pressure points in that location where the plaques
or welts are arising. You didn't say what type of saddle you're using &
much about your riding experience, but either your weight is back a
little or the saddle doesn't spread out the weight over a big enough
surface. These pressure points are <not> dependant on heat. They were
called "heat bumps" years ago before folks recognized them for what they
were.
If you are willing to try a "patch fix", get a good pad - foam or gel -
to redistribute the weight. I've found natural wool pad covers do
better for "thin-skinned" horses as compared to synthetics. The better
but infinitely more expensive option is to get a new saddle that helps
to eliminate the problem. It is very hard to try out a saddle for 5 hrs
and still be able to return it. Some manufacturers do offer such a
guarrantee, so ask before you buy. (You have more leverage with the
seller before the deal has closed.)
Ask somebody to evaluate your seat and riding style. They may be able
to offer suggestions to help you balance & distribute the weight better.
Good luck.
Linda Flemmer
Blue Wolf Ranch
Bruceton Mills, WV