  We present a theoretical study of the influence of resonant enhancement on
quantum path dynamics in the generation of harmonics above and below the
ionization threshold in helium. By varying the wavelength and intensity of the
driving field from 425 nm to 500 nm and from 30 TW/cm${^2}$ to 140 TW/cm${^2}$,
respectively, we identify enhancements of harmonics 7, 9, and 11 that
correspond to multiphoton resonances between the ground state and the Stark
shifted $1s2p$, $1s3p$, and $1s4p$ excited states. A time-frequency analysis of
the emission shows that both the short and long quantum path contributions to
the harmonic yield are enhanced through these bound state resonances. We
analyze the sub-cycle time structure of the 9th harmonic yield in the vicinity
of the resonances and find that on resonance the long trajectory contribution
is phase shifted by approximately $\pi/4$. Finally, we compare the single atom
and the macroscopic response of a helium gas and find that while the sub-cycle
time profiles are slightly distorted by propagation effects, the phase shift of
the long trajectory contribution is still recognizable.

Atomic Physics;Optics;Quantum Physics