In the history of Chen Style Taijiquan, the 8th generation had a master named Chen Xin陳鑫 (1849 – 1929) who was famous for his writing and his Taijiquan as well. If we study Chen Taijiquan we should all read his book as is describes a lot of knowledge, detail and principles of Chen Taijiquan.
In one part of his book he says, “Body feels light and keep energy externally. Qi sinks to the Dantian虚領頂勁，氣沉丹田.” This is the attitude when we practise Chen Style Taijiquan. It means the body should feel light, but not collapsed and weak. It also has energy which is external and strong, which means firm outside. So all together is means firm on the outside, but at the same time light on the inside. When the Qi flows through the entire body we will have that feeling. By doing the form we sink the Qi to the Dantian and this means the weight must be on our legs. When the Dantian is full and so the body will be lighter. The lighter we are the more we can feel if the body’s posture is good and correct. If it is, then the external body will be firm.
All of this means that we sink the Qi to the Dantian to keep the body light, the posture correct so the whole body is connected and then we have sense and have awareness through our skin.