A friend of mine has a young Gelding who is in training with the US Olympic Dressgae Trainer - I know she always lunges, and while he is getting ready I believe he has a magnetic rug on!
One of the hirelings is, she is always walked in hand briskly at meets for 5-10mins before beign saddled and tehn again for another 5mins. Her riders are always given legups and we try to keep her being ridden by lightish riders.
I had a cold backed horse - made sure he was warmed up before mounting and didn't sit in the saddle till he'd moved off - stood in stirrups until his back came down and then sat very lightly for the first couple of hundred yards. He was absolutely fine after that. I used the big felt pads under his saddle, then tried a jelly pad, which I really thought was good.
Had a McTimony chiropracter who really helped - it was like riding a different horse and seemed to strengthen him behind.
A friend has a big 17hh young horse who is a bit cold backed and collapses away. He is quite weak behind, so all and any schooling that helps him to build up his back end muscles all helps.
I know of a racehorse who is cold-backed, don't actually know how much, but they tack him up then put him on the walker for 10 min, then got on him lightly and let settle, was fine after that
Obviously the horse needs to be checked out to ensure that there is no physical problem causing the cold-back. Know several cold-backed horses and the usual strategy is to girth them up slowly and either walk them in-hand or lunge them before mounting. Some cold-backed horses are also more comfortable in an elasticated girth.
Mum's idxarab is cold backed but as mentioned above not mounting from ground, walking round for 5 mins beforehand, taking a light seat untill he is happy, and chiropracter have made all the difference to him. We always school him in a "free walk" kind of stretch for first 10-20 mins in all three paces, not ideal for everyone/situation but stops him rushing away from riders seat.
Miss Delia was mildly cold backed - would dip and be uneven behind.
She had no physical problems and saddle fitted well. Was worse in winter.
Used to put on saddle and do up girth just enough to keep saddle in place and leave for 5 minute to warm up. Then slowly did up saddle.
Always used mounting block and stood in saddle and allowed her to walk forward for 10 or so steps before sitting gently down. If she started to dip, stood again in stirrups with weight forward for a further 10 steps. Never had to do this a third time.
I was at a show last week and saw a really good product called thinline just come over from america apparently, quiet big over there. There really thin i think there website was www.maddocks-saddlers.co.uk. A new company i think. The pads were like quarter of the thickness of a prolite pad yet still 95% shock absorbent.