Let f : U → R 2 be a continuous map, where U is an open subset of R 2 . We consider a fixed point p of f which is neither a sink nor a source and such that { p} is an isolated invariant set. Under these assumption we prove, using Conley index methods and Nielsen theory, that the sequence of fixed point indices of iterations {ind( f n , p)} ∞ n=1 is periodic, bounded from above by 1, and has infinitely many non-positive terms, which is a generalization of Le Calvez and Yoccoz theorem (Annals of Math., 146, 241-293 (1997)) onto the class of non-injective maps. We apply our result to study the dynamics of continuous maps on 2-dimensional sphere.