  Context. Precise determination of stellar masses is necessary to test the
validity of pre-main-sequence (PMS) stellar evolutionary models, whose
predictions are in disagreement with measurements for masses below 1.2 Msun. To
improve such a test, and based on our previous studies, we selected the AB
Doradus moving group (AB Dor-MG) as the best-suited association on which to
apply radio-based high-precision astrometric techniques to study binary
systems. Aims. We seek to determine precise estimates of the masses of a set of
stars belonging to the AB Dor-MG using radio and infrared observations.
Methods. We observed in phase-reference mode with the Very Large Array (VLA) at
5 GHz and with the European VLBI Network (EVN) at 8.4 GHz the stars HD 160934,
EK Dra, PW And, and LO Peg. We also observed some of these stars with the
near-infrared CCD AstraLux camera at the Calar Alto observatory to complement
the radio observations. Results. We determine model-independent dynamical
masses of both components of the star HD 160934, A and c, which are 0.70+/-0.07
Msun and 0.45+/-0.04 Msun , respectively. We revised the orbital parameters of
EK Dra and we determine a sum of the masses of the system of 1.38+/-0.08 Msun.
We also explored the binarity of the stars LO Peg and PW And. Conclusions. We
found observational evidence that PMS evolutionary models underpredict the mass
of PMS stars by 10%-40%, as previously reported by other authors. We also
inferred that the origin of the radio emission must be similar in all observed
stars, that is, extreme magnetic activity of the stellar corona that triggers
gyrosynchrotron emission from non-thermal, accelerated electrons.
