chest movement

once you have the basic posture of xingyiquan its time to start thinking about what kind of internal movement you can make to develop more power. Xingyi focuses on sinking the chest and rounding the upper back, but there is more to the chest than just that requirement. To achieve power in certain movements the chest has to do one of three things:
1) sink and close: This is useful in vertical movements such as pi quan, where the power created by the chest rounding closed develops the jin of the movement.
2)open and close: this is important in many animal movements. In the deffensive part of the movement the chest opens up and then on the attack the chest closes and rounds inward. This is a more advanced method of jin development and allows for more power to be obtained, but requires the situation to be right if it is to be applied practically.
3) horizontal waving of the chest: this is important in some animal movements such as swallow. This especially useful when going from defense to attack in movements that go straight forward such as moves with beng quan contained in them.
Not many people talk actively about the role of the chest in xingyi so I just wanted to throw this out there for anyone who is interested.