Torsion applied to a slender soft rod can cause the rod to lose its stability and knot — a phenomenon widely referred to as the torsional instability of elastic rods. Previous studies mainly focus on predicting the critical load, at which the torsional instability occurs, and investigating the post-instability deformation of the rod. Thus far, little attention, if any, has been paid to exploiting the torsional instability of hyperelastic soft rods to realize functions such as actuation. In this work, we study the twisting process of hyperelastic soft rods through dimensional analysis and explicit finite element method, and find that the axial pulling force of the soft rod suddenly rises drastically immediately after the torsional instability occurs. Further simulations demonstrate that the sharply increased pulling force can be utilized to achieve a large-stroke pulling actuation. The influence of the rod geometry and material properties of the rod on the actuation forces/strains is also discussed. The results of this work are expected to guide the design of novel actuators based on the torsional instability of hyperelastic soft rods.