I wear a back brace all the time in the surf to aid in the maintenance of a nasty lumbar injury. I think back braces work for two main reasons:
1 - they help create blood flow in the area which keeps the area warm both before/during and after the sesh and:
2 - they remind you that you have a problem and make you aware that you need to be a bit more careful and especially on a sup - not over twist, which causes havoc to backs.

They are a great idea.

Hey Phil, my neurosurgeon in Sydney advised me to go to a guy in sydney to get a custom made lumbar/sacral support made. At the time I couldn't afford it (about $500) so I got a brace from a company called Medical Accessories Australia. Their contact number is 07 5508 2720. If you ring them they can send you a catalogue. They have a great range of brace/supports and they are reasonably priced (around $100), I wear mine surfing and supping and it gives amazing support. If you have any trouble getting hold of them PM me and I will send you my catalogue.
Bill

I have found the neoprene ones stretch too much and when they get wet they need adjusting and that aint too easy when you are out in a steamer trust me. they suggest you put the neoprene ones on wet to avoid the stretch. The one I use is awesome and you can check the range out at the shop at 1/60 Township Drive. Can check mine out if you ever toughen up and get back into the surf The type I use adjusts up prior to getting wet and doesn't give when it gets wet. It has two metal supports but have taken them out because there is enough support without them. They also make you look 20 years younger (well, some of us - they aint magic )

It's good to hear others are finding a back belt useful, I've got two herniated discs and have worn a weight lifters support belt for the last six months under my wettie when SUP surfing, it just gives the support I need and means I can surf for a couple hours without back pain afterwards.
These belts have a 4 or 5" neoprene type support at the back which is cut lower in the front and a nylon webbing belt all the way round with velcro on it which you cinch up through a metal buckle, as tight as you need it.
This belt has worked great for me and they are cheap to buy.

I will just add some more now I've read every thing proberly (dick head) .Ihave not had problems with stretching .
tow ball

Pilates does wonders for lower back injuries and strains. Make sure you visit one that is linked to physio as the treat-all pilates class at some gyms is a general stretch and may not be suitable for specific complaints. My 2c worth.