Recently, the inertial parameter regrouping method was presented to reduce the computational burden of the robot inverse dynamics algorithm. This paper describes how to apply the method to two widely used forward dynamics algorithms (i.e. Featherstone's articulated-body inertias algorithm and Walker & Orin's composite body algorithm) to increase their efficiency. It is proved that the inertial parameter regrouping method can be applied to the articulated-body inertia algorithm by simply replacing the original spatial inertia matrices with the new ones consisting of the regrouped inertial parameters. In addition, by the use of Gautier & Khalil's regrouping method the composite body algorithms is reformulated in a more computationally efficient form.