  In this talk I concentrate on the role of chiral symmetry realisation by
spin-1 fields in the low energy QCD effective lagrangian. I assume that chiral
symmetry is nonlinearly realised and that spin-1 fields transform homogeneously
under chiral rotations, which is in sharp contrast to previous works where the
$\rho$ and the $a_1$ mesons were treated as approximate gauge bosons of some
chiral group. I emphasise the role played by four-meson couplings which in our
scheme are essential for the theory to make sense. By requiring the kinetic
energy density of the theory to be bounded from below we find inequalities
relating three- and four-point meson couplings. It is finally shown how the
combination of our analysis and of unitarity requirements naturally leads to a
low-energy phenomenological lagrangian for the nonanomalous sector of $\pi\rho
a_1$ strong interactions.
