Summary form only given. Spherical tokamaks are low-aspect-ratio devices with plasmas that are roughly spherical in shape. To create low-aspect-ratio plasmas, the center column of the tokamak must have as small a diameter as possible. The center column must include conductors to carry the toroidal field current and may also include space for an ohmic heating (OH) solenoid, unless non-inductive methods are used to start and maintain the plasma current. All spherical tokamaks designed to date include an OH solenoid. The authors discuss some possible designs for the central column.