Holding the Moon is a traditional posture for most Chinese internal martial arts. If you practice Holding the Moon before you are aware of your shoulder and hip alignment, however, you can reinforce bad posture. Therefore, a good way to learn the posture is lying on the floor.
Lie down on the floor with your feet hip width apart, your arms extended to your sides, and your toes pointing to the ceiling. Pull your feet up by bending your knees until your feet are flat on the floor. Raise your arms up from the sides, bending them at the elbows, until your shoulders start to rise off the floor. Gravity should pull the elbows and hands down so it looks like you are holding a large ball on your chest. Hold this position for up to five minutes.
In this posture, gravity is trying to pull your arms in any number of directions. If you think of gravity as being water, you can imagine that currents are flowing through the water, trying to push your arms down to the floor by dragging them over your head, or by pushing them out to the sides. You are resisting the flow of water, holding your arms up with your hands over your shoulders.
You want to supply just enough resistance in the arms to keep them in the correct position. This idea of providing just enough tension to hold the position is called sung. Sung is often translated as relax, but you do not want to relax so much that you become a bowl of jelly. Holding the Moon on the Floor posture is a good way to experience this idea of sung. Since the rest of your body is being supported by the floor, you can put your attention on the arms. Try different levels of tension and relaxation in your arm muscles as you breathe deeply. When you find a combination that feels most comfortable, you have achieved sung.
The standing version of Holding the Moon Posture is one of those exercises that looks really simple, but can be a serious chal-lenge, especially if your hips and shoulders are weak. Once you are comfortable with the Wuji Posture, you can add Holding the Moon to your standing practice by raising the arms straight out to shoulder height and letting the elbows sink down and away so the palms turn inwards.
When you are in the standing posture, gravity is pulling down on the arms, like they are sinking into the water. This sinking feeling is called chen. Once you become familiar with sung and chen in your arms, start putting your attention on other parts of your body, and applying these principles. For example, your shoulders should be pulled back, with the shoulder blades under your ears, relaxed, and sinking to the ground.