  Within the framework of two-flavor covariant baryon chiral perturbation
theory we have expressed the Chernyak-Zhitnitsky, Ioffe and Dosch currents in
terms of chiral fields to provide leading one-loop extrapolation formulae for
the leading and next-to-leading twist normalization constants $f_N$,
$\lambda_1$ and $\lambda_2$. Finite volume effects due to pion loops have been
taken into account. The occurring low energy constants are fitted to data
obtained from recent lattice QCD simulations in order to extract the values at
the physical point.
