  We present a unified theory for the longitudinal dynamic response of a stiff
polymer in solution to various external perturbations (mechanical excitations,
hydrodynamic flows, electrical fields, temperature quenches ...) that can be
represented as sudden changes of ambient/boundary conditions. The theory relies
on a comprehensive analysis of the non--equilibrium propagation and relaxation
of backbone stresses in a wormlike chain. We recover and substantially extend
previous results based on heuristic arguments. Intriguing new experimental
implications are pointed out.
