"Discussion with Master Ma Hai long about Tai Ji Quan theory". A few days ago he sent me a handwritten letter about Xu Jin and Ting Jin theory. 

In a world of martial arts where people keep hiding knowledge is such a great sign from a man like him still showing his desire to share quality information with people.

With great pleasure, I share with you this quick translation of his letter:

关于太极拳的一些名词的解读
Explanation of some terms in Tai Ji Quan 

在太极拳的传统理论中,有一些专用名词,由于后人在解释中,往往限於个人的理解,或者是认识上的局限,存在不同的度上的片面性,往往会产生一些误差。例如:
In the traditional Tai Ji Quan Theory, there are some terms explained by people of later generations limited by their own understanding or lack of knowledge. There are usually some mistakes or one-sidedness. 

For example:
1.蓄劲:Accumulate and preserve the force
简单地说,“蓄劲”就是对于太极拳修炼的积累。它指的是全面性的,而不是局部。俗语说:外炼筋骨皮,内炼一口气。而总称就是“蓄劲”。这是任何一项运动都需要的。
In simple terms, “Xu Jin” is the accumulation of Tai Ji Quan’s practice. It refers to a comprehensive accumulation, not just one part. We have the old saying: “ Outside practice the muscles/tendons, bones and skin (It can be also translated as tissues), inside cultivate the Qi. (It can be also translated as practice a mouthful of breath” Altogether is “Xu Jin”, and this is necessary for any kind of physical activity. 

2.听劲:Ting Jin 
我的解释是修炼者对外来攻击的反映。其中,就是《拳经》上所说的,“得机得势”。“听劲”的反映,我认为应是由三方面组成。1.准确度Accuracy; 2.精密度Precise;3.灵敏度Sensitivity 组成。他们的关系应为:
这三者之合,就是“听劲”。 
My way of explaining Ting Jin is: “reacting to other practitioners’ attack”. Like it says in the book <Quan Jing>, “Gain the opportunity, gain [superior] positioning”. I think “Ting Jin” should be composed of 3 aspects. 1. Accuracy; 2. Precision; 3. Sensitivity. The relation of the 3 should be:
Combine them together, you have “Ting Jin”.

August 2019 - Letter from Master Ma Hai Long to Mauro Antonino D'Angelo