How can you reduce back pain while standing at work?

Refer to answer: Need to stablish the cause. In general a back brace, and exercise is a good start. If pain persists refer to your physician.

Don't stand too long: You can try to change your foot position by resting one and alternating them on a book or footstool simulating a brass rail in a bar. Just walking a few steps periodically or squating can help. Some pelvic tilts can help as well as a simple elastic back support. Weight control, regular exercise and not smoking ( if you do) will also help. Sometimes a local heat application can help -otc patches.

Muscle strength: Best way to reduce back pain is to be as light as you can (optimal weight) be as fit as you can (high level of fitness with good core muscle strength) and don't smoke. The intermittent use of anti-inflammatory medications will help as well.