  We consider the two-dimensional $\rm O(3)$ non-linear sigma model with
topological term using a lattice regularization introduced by Shankar and Read
[Nucl.Phys. B336 (1990), 457], that is suitable for studying the strong
coupling regime. When this lattice model is quantized, the coefficient $\theta$
of the topological term is quantized as $\theta=2\pi s$, with $s$ integer or
half-integer. We study in detail the relationship between the low energy
behaviour of this theory and the one-dimensional spin-$s$ Heisenberg model. We
generalize the analysis to sigma models with other symmetries.
