  We study analytically and numerically a generic continuum model of an
isotropic active solid with internal stresses generated by non-equilibrium
`active' mechano-chemical reactions. Our analysis shows that the gel can be
tuned through three classes of dynamical states by increasing motor activity: a
constant unstrained state of homogeneous density, a state where the local
density exhibits sustained oscillations, and a steady-state which is
spontaneously contracted, with a uniform mean density.
