Inhale with nose and hold breath. Place palms and rub them until they get warm and then use palms to rub both sides of lower back whilst slowly exhaling with nose. The "gate of jing" refers to the two soft spots on lower back. Rub them 36 times before sitting quietly for a whilst at the end of the whole process.
This exercise may reinforce kidney qi, nourish the five zang organs and dispel cold and dampness.