"Compared to traditional massage, the pressure applied with manual lymph drainage is much lower in intensity. The goal of these techniques is to manipulate the lymphatic structures located in the subcutaneous tissues. In order to achieve the desired effect, the pressure in the working phase should be sufficient enough to stretch the subcutaneous tissues against the fascia (a structure separating the skin from the muscle layer) located underneath, but not to manipulate the underlying muscle tissue.
The amount of pressure needed in MLD is sometimes described as the pressure applied stroking a newborn’s head.
In the resting phase of the stroke the pressure is released, which supports the absorption of lymph fluid into lymph vessels. To achieve the maximum effect with each technique, the working phase with every stroke should last about one second and should be repeated five to seven times.
The overall goal of MLD in the treatment of lymphedema is to re-route the flow of stagnated lymphatic fluid around blocked areas into more centrally located healthy lymphatic vessels, which eventually drain into the venous system."
Source: Joachim Zuther's Lymphedema Blog