  We compute the temporal evolution of the pressure anisotropy and bulk
pressure of a massive gas using second-order viscous hydrodynamics and
anisotropic hydrodynamics. We then compare our results with an exact solution
of the Boltzmann equation for a massive gas in the relaxation time
approximation. We demonstrate that, within second-order viscous hydrodynamics,
the inclusion of the full set of kinetic coefficients, particularly the
shear-bulk couplings, is necessary to properly describe the time evolution of
the bulk pressure. We also compare the results of second-order hydrodynamics
with those obtained using the anisotropic hydrodynamics approach. We find that
anisotropic hydrodynamics and second-order viscous hydrodynamics including the
shear-bulk couplings are both able to reproduce the exact evolution with
comparable accuracy.
