Chiral symmetry constraints on resonant amplitudes

We discuss the impact of chiral symmetry constraints on the quark-mass dependence of meson resonance pole positions, which are encoded in non-perturbative parametrizations of meson scattering amplitudes. Model-independent conditions on such parametrizations are derived, which are shown to guarantee the correct functional form of the leading quark-mass corrections to the resonance pole positions. Some model amplitudes for $\pi \pi$ scattering, widely used for the determination of $\rho$ and $\sigma$ resonance properties from results of lattice simulations, are tested explicitly with respect to these conditions.