  Nucleon generalized polarizabilities are investigated within a relativistic
framework, defining such quantities through a Lorentz covariant multipole
expansion of the amplitude for virtual Compton scattering. The key physical
ingredients in the calculation of the nucleon polarizabilities are the Lorentz
invariant reduced matrix elements of the electromagnetic transition current,
which can be evaluated from off-energy-shell helicity amplitudes. The evolution
of the proton paramagnetic polarizability, $\beta_{para}(q)$, as a function of
the virtual-photon three-momentum transfer $ q,$ is explicitly evaluated within
a relativistic constituent quark model by adopting transition form factors
obtained in the light-front formalism. The discussion is focussed on the role
played by the effects due to the relativistic approach and to the transition
form factors, derived within different models.
