  We present calculations of axial-current matrix elements between various
heavy-meson and heavy-baryon states to the next-to-leading order in heavy
hadron chiral perturbation theory in the p-regime. When compared with data from
lattice computations or experiments, these results can be used to determine the
axial couplings in the chiral Lagrangian. Our calculation is performed in
partially-quenched chiral perturbation theory for both SU(4|2) and SU(6|3). We
incorporate finite-size effects arising from a single Goldstone meson wrapping
around the spatial volume. Results for full QCD with two and three flavours can
be obtained straightforwardly by taking the sea-quark masses to be equal to the
valence-quark masses. To illustrate the impact of our chiral perturbation
theory calculation on lattice computations, we analyse the SU(2) full QCD
results in detail. We also study one-loop contributions relevant to the heavy
hadron strong-decay amplitudes involving final-state Goldstone bosons, and
demonstrate that the quark-mass dependence of these amplitudes can be
significantly different from that of the axial current matrix elements
containing only single hadron external states.
