《论衡·卷七·道虚篇》
道家或者用练气功来保养生命，成仙不死，认为血脉在身体中，如果不活动，不弯曲舒展，就会闭塞不通。
道家或以导气养性，度世而不死，以为血脉在形体之中，不动摇屈伸，则闭塞不通。
Taoists either use qigong to maintain their lives and become immortals and never die. They believe that the blood vessels in the body, if not moving, not bending and stretching, will become blocked and impassable.