We present a new method for the modeling and animation of deformable and flexible thin or thick linear bodies. Our method highly reduces the computation required to animate deformations and motions of objects with a cylindrical topology, while preserving their visual quality and their control. To increase the speed we introduce a bi-layered mass-spring system with two main properties: it is not constructed as the whole geometric mesh thus limiting the number of dynamically computed points, and it is partly constrained to reduce physical computations. The visual quality is improved with an appropriate integration scheme to preserve volume as much as possible and to ensure high stability at low cost. The two mass-spring layers and their linkage provide all the required controls on the objects: the first layer, corresponding to an axial flexible backbone structure, is used as a controller for global motions. The second layer, geometrically and dynamically constrained, controls envelope elastic deformations.