After poking and prodding me, testing my reflexes, and examining just where the numbness was, my doctor says that I appear to have injured my L4 disk. My reflexes are good, and the injury may be relatively minor. There are treatments such as steroids and surgery if nothing improves, but for now the instructions are to lay off of heavy lifting and other things that might exacerbate the injury. Continuing to lose weight won't hurt, either, as it will reduce strain. These things sometimes clear up on their own. We'll re-assess the situation at my next quarterly exam or if the condition worsens.
This does mean that other people are going to have to lug that darned mimeograph out of the back of my van once I reach the loading dock at Denvention Three, for I cannot risk lifting it.