  We show that the relativistic dissipative hydrodynamic equation derived from
the relativistic Boltzmann equation by the renormalization-group method
uniquely leads to the one in the energy frame proposed by Landau and Lifshitz,
provided that the macroscopic-frame vector, which defines the local rest frame
of the fluid velocity, is independent of the momenta of constituent particles,
as it should. We argue that the relativistic hydrodynamic equations for viscous
fluids must be defined on the energy frame if it is consistent with the
underlying relativistic kinetic equation.
