  The elastic response in polymeric gels is studied by means of a percolation
dynamic model. By numerical simulations the fluctuations in the gyration radius
and in the center of mass motion of the percolating cluster are determined.
Their scaling behaviour at the gelation threshold gives a critical exponent for
the elastic modulus $f \sim 2.5 \pm 0.1$ in agreement with the prediction $f =
d \nu$.
