I've been fighting miserable back pain for the past couple of months so I can offer up a few things I've learned in that time. My situation isn't due to one single issue, but rather several small issues that combined to make it bad. First off, I have a bad genetic package for standing for long hours. I have an extra vertebrae (which isn't too uncommon), meaning my spine is tweaked a bit more than usual. Also, I have next to no arches in my feet. So unfortunately, my situation is exacerbated due to some bigger issues. However, I feel that this just brought about the symptoms faster, as just standing with bad shoes will lead up to problems as Phaelon mentioned.
The second issue that caused me problems is what you mention, shoes. For the past several years, I've worn either low soled Pumas or Adidas Sambas. While looking cool, there isn't any support or cushion. To try to fix my back, I looked into getting special server shoes. Talking to the chiropractor, the key for standing is proper foot support and cushion. The server shoes have good cushion, but a pair of running shoes can also provide the necessary cushion. So don't feel you have to get server shoes. To get proper foot support, you need to have some good insoles. Fortunately, my insurance covered a custom fitted pair of orthotics by Foot Levelers
. If you have insurance, find out if you can get a pair. If not, they'll run you about $300. I can't vouch for the over-the-counter insoles, as I haven't had much success with them. But perhaps if your situation isn't as bad, they'll do a good job.
Finally, make sure your environment is set up properly. While there is always something to do behind the bar during a shift, perhaps you can have a stool behind the bar to sit when you're talking with co-workers or writing something down. Just getting off your feet for a couple minutes will be helpful for you in the long run. Secondly, there needs to be rubber padded mats behind your bar, something that looks like these
. Not only do they provide more cushion for your back, feet and knees, but they'll keep you safe from slipping and save a few dropped glasses and demitasses. And last, stretch before and after work. It always sounds lame to talk about stretching before work, as I always conjure up the Sit & Be Fit people:
However, stretching and all these other things are necessary to make sure we can be baristas for years to come. I hope that we can all be proactive in ensuring our bodies stay healthy to make sure we don't have to leave the industry earlier than we'd like to.