A reformer exercise apparatus has a generally rectangular frame and a pair of spaced-apart parallel tracks or rails joining a head end and a foot end. The module also comprises a thermal safety device for the circuit. The at least one sub-electrode has a width which is less than a width of the base electrode to impart a generally tapered, stepped or convex configuration to the current-leveling electrode. This, combined with the invention of self-describing file systems, makes it possible to build applications that are more intelligent and perform better than their counterparts that either embed knowledge of a file system or rely on a file system driver to interpret the structure on behalf of the applications.