Many important biopolymers can be very accurately described by the wormlike chain model. A unified theory that has recently been established allows to systematically analyze the longitudinal dynamics of semiflexible polymers far from equilibrium under external perturbations. We present analytical and numerical results for three different problems: - an longitudinal force applied at the ends of a filament equilibrated under some prestretching force induces backbone tension that spreads into the bulk. How fast? - a very straight conformation could be due to a large stretching force as well as to a small temperature environment. How does then a straight polymer relax? - a transverse force also leads to longitudinal stretching and the propagation of backbone tension. How?