"it is at the extremities (Jing-Well points) that the Qi changes direction" (TCM theory)
is not as important as the quality of energy described at each of the points. The Jing-Well points, for example, are situated on the tips of the fingers or toes, where there is little flesh. The Qi here is shallow and narrow, yet
dynamic, pouring forth like a spring or a well. The volatility of the Qi at these points is emphasised by the fact that in the theory of the circulation of the 12 channels,
it is at the extremities (Jing-Well points) that the Qi
changes direction and where Yin and Yang channels
transform into each other.
JOURNAL OF CHINESE MEDICINE NUMBER 42 MAY 1993