For two years I have had intermittent middle back spasms after bending and then straightening. They have been sudden and severe, but last only a moment. A month ago I was simply walking across a room when I experienced a sudden and very severe middle back spasm that lasted four days, but slowly got better over that period. Since then, I have experienced more moderate and less long term spasms that seem to be brought on by raising my hands overhead when washing or drying my hair. These last up to a couple of hours and heal with rest. The first, four day attack was on my left side. The subsequent ones are on the right. Should I worry about my spine or is this likely to be a muscle problem. I have a desk job and only exercise by walking a half-hour per day.