We tested the responses of single, isolated lymphangions to selective changes in preload and the effects of changing preload on the response to an imposed afterload. The methods used were similar to those described in our companion paper. Step-wise increases in input pressure (P_in; preload) over a pressure range between 0.5 and 3 cmH₂O, at constant output pressure (P_out), led to increases in end-diastolic diameter, decreases in end-systolic diameter, and increases in stroke volume. From a baseline of 1 cmH₂O, P_in elevation by 2–7 cmH₂O consistently produced an immediate fall in stroke volume that subsequently recovered over a time course of 2–3 min. Surprisingly, this adaptation was associated with an increase in the slope of the end-systolic pressure-volume relationship, indicative of an increase in contractility. Lymphangions subjected to P_out levels exceeding their initial ejection limit would often accommodate by increasing diastolic filling to strengthen contraction sufficiently to match P_out. The lymphangion adaptation to various pressure combinations (P_in ramps with low or high levels of P_out, P_out ramps at low or intermediate levels of P_in, and combined P_in + P_out ramps) were analyzed using pressure-volume data to calculate stroke work. Under relatively low imposed loads, stroke work was maximal at low preloads (P_in ∼2 cmH₂O), whereas at more elevated afterloads, the optimal preload for maximal work displayed a broad plateau over a P_in range of 5–11 cmH₂O. These results provide new insights into the normal operation of the lymphatic pump, its comparison with the cardiac pump, and its potential capacity to adapt to increased loads during edemagenic and/or gravitational stress.