A 32-year-old multiparous woman (G3P2) at 40 weeks gestation presents in active labor. On vaginal examination, the cervix is fully dilated (10 cm), 100% effaced, and the fetal head is at +1 station. The patient has a strong urge to push and is bearing down with contractions. Fetal heart rate is 138 bpm with good variability. What is the expected duration of the second stage of labor in this multiparous woman, and what is the primary maternal effort during this stage?