Conventional sucker rods are used to drive progressing-cavity-pump (PCP) systems. However, conventional rods were designed to work under alternating tensile stress, not under torsion (shear stress). The use of conventional rods to drive PCP systems has limitations and problems. A PCP requires a high-torque rod to drive the system. A hollow-rod (HR) system was developed that reduces connection failure and tubing wear, increases pumping rates as a result of high torque capacity, and enables injection of chemical corrosion inhibitors or viscosity-reduction fluids down the inside of the HR.