  Mechanical oscillations are important for many cellular processes, e.g. the
beating of cilia and flagella or the sensation of sound by hair cells. These
dynamic states originate from spontaneous oscillations of molecular motors. A
particularly clear example of such oscillations has been observed in muscle
fibers under non-physiological conditions. In that case, motor oscillations
lead to contraction waves along the fiber. By a macroscopic analysis of muscle
fiber dynamics we find that the spontaneous waves involve non-hydrodynamic
modes. A simple microscopic model of sarcomere dynamics highlights mechanical
aspects of the motor dynamics and fits with the experimental observations.
