In this paper we present a new methodology for dynamic movement planning of digital human models in constrained environments. The goal is to compute a smooth trajectory of centre of mass (CoM) that satisfies dynamic constraints throughout the whole motion. Firstly, we adapt a newly proposed dynamic stability criterion in order to define stability constraints in this work. This criterion is then used to analyze human motions from the viewpoint of stability. Then we apply the approach to compute trajectories of CoM by implementing parametric splines and optimization methods with dynamic constraints. Finally we apply the generated trajectory in a whole-body simulation in order to demonstrate the viability of this approach.