Chán Sī Jìng 纏絲勁 has Shùn Chán Sī Jìng 順纏絲勁– outward circle and Nì Chán Sī Jìng 逆纏絲勁– inward circle. If we have good Nèi Gōng 內功 (Internal Power) then our Chán Sī Jìng will be even more powerful. Nèi Gōng comes from our practice of stance and forms. Chén Tàijíquán requires a low stance and so more weight is placed on the legs. If we practise a lot of Zhàn Zhuāng 站樁 this will build up our Nèi Gōng (which is the same as Gōng Lì 功力. In Wing Chun 詠春 practise we are used developing our Gōng Lì and this is the same as Nèi Gōng), then when we use Chán Sī Jìng we will have more power to push our opponents. If we have Shùn Chán Sī Jìng, then we can push even better, as we will make our opponent circle and so the will lose their balance as the circle rolls round. If the circle is clockwise, then the opponent will roll clockwise. It is the same with Nì Chán Sī Jìng, the opponent will lose their balance as we roll our circle. If our circle is anticlockwise, then they will lose their balance and fall anticlockwise.
When we practise Chán Sī Jìng, our movements must come from the Dāntián 丹田, but when we practise Tuī Shǒu 推手 it might come from our hands, our body or legs, whichever part is in contact with the opponent. So we must remember sometimes it comes from the Dāntián and sometimes from where we contact.