Your body is subject to a lot of stress everyday. i know. i used to work a job that required me to stand for very long periods of time. So I developed a system that allowed me to do some Tai chi while I was standing; simple stuff, nothing complex.
There is one exercise that's called "hold the ball." This is where you bend your knees slightly, (this allows the blood to circulate better), and then you relax your arms naturally into their sockets. In China, Tai chi and Chi Gong practitioners hold this position for hours at a time. Our Tai chi instructor, (who was also a physiologist at NASA), showed us how our body tenses up and simply by relaxing your arm and a little nassage, your arm increases its length by several inches.
Another exercise simply involves using the center of energy that your body has. This is located in the solar plexus, a sort of spiral ball of energy at the center of your body. Bu relaxing the body and twisting from side-to-side at the hips, you can increase your energy and stand for a long time without any pain.
You can relieve stress on your back even if you work in an office and are sitting down all day. First of all, see if you can get a chair that has lumbar support. Then breal up the monotony by getting up and stretching every once-in-awhile. remember, sittiing for a long period of time can cause blood to pool in your legs and form blood clots. While you are sitting, you can use neck exercises to get the chi flowing throughout your body.