After a few minutes of warming up do they then act normal???
To me it is all of the above and has alot to do with saddle fit.
Do we worry enough about how are saddles fit? I have tried to run a few posts on saddle fit but I get nowhere.
Yes you lood at the sweat marks and a dry spot means NO pressure, maybe even no contact of the saddle tree.
If your horse exibits anyone of the above then maybe you should have a close look at the saddle fit and I don't mean just throwing the saddle on and eyeballing the contact. With an english or western saddle the padding makes eye balling impossible.
I once stated that I am ANNAL about most things and my horse is no exception. His saddle must fit. Each guy I buy gets a custom fit.
The trees are removed from the saddle, the tree is custom filled,filed or modified in some way to fit his back and only after I have full contact do I reassemble the saddle.
I find ALL saddles that the tree bridges the back. A western saddle is like putting a chair on the back. It contacts at the front, the withers but only marginally, the slope at the withers is wrong for my arabs .
I find the ends of the tree dig into the back at the loins.
I have to fill some areas about 1/2 inch to prevent bridging.
I also change the rigging so the cinch doesn't pull right down on the withers. If you look at most western saddles the girth is in front of the leg to prevent interference with the free swing of the stirrup . This is for the convenience of the rider but what about the horse.
English saddles are better in the placement of the cinch.
I have custom made billets that adapt an english 24 inch girth to the wester saddle putting the girth directly in the center of the saddle and well back from the shoulder.
Fit the saddle properly and you might be suprised that some problems go away