Light Body, Turn Easily, Qi Flows Through the Whole body and Reaches the Feet輕靈圓轉，中氣貫足
This phrase is hard to understand if you have not practised Taijiquan for a long time. A long time means at every day for at least 3 years. If we miss one day, then the next day we must practise twice as much. This is how a good Taiji master practises, they practise every single day 10 forms or more every day. Myself, I practise 2 times Xinjia Pao Chui新架砲捶,2 times Laojia Pao Chui老架砲捶, 1 times Xinjia新架—路 and 1 times Laojia老架一路, so six forms every day. Why only 6? This is because I need to practise my of Kung Fu forms (like Chun Yuen Quan) and Qigong as well. There are also many weapons forms in Taiji Quan to practise like, Spring and Autumn Da Dao春秋大刀, Pear Blossom and White Monkey Spear梨花槍與白猿棍, Double Broadswords雙刀, Double Swords雙劍, 13 Long Pole十三杆 etc, so there is a lot to practise! I like practise hard forms forst then the slow forms later. However bare hands forms are the most important, because these teach us the principles of Taijiquan, and when we can follow those principles, after many years we will find ourselves feeling lighter and our footwork will be fast and strong. We can turn easily and are solid when we land, we will not be tired easily and our legs will feel full of Qi and they are light and strong. This is what Chen Xin was saying. A lot of skill we need to practise a lot and then we can understand what our Taiji ancestors meant.