  One of the systematic errors in some of the current lattice computations of
the HVP contribution to the muon anomalous magnetic moment $g-2$ is that
associated with the extrapolation to the physical pion mass. We investigate
this extrapolation assuming lattice pion masses in the range of 220 to 440 MeV
with the help of two-loop chiral perturbation theory, and find that such an
extrapolation is unlikely to lead to control of this systematic error at the 1%
level. This remains true even if various proposed tricks to improve the chiral
extrapolation are taken into account.
