ENCYCLOPEDIA OF TAOISM (SYNOPSIS FOR MYSELF): Zhŏngxī 踵息 breathing through the heels

““Breathing through the heels” is first mentioned in the Zhuangzi 6, which states that “the Real Man (zhēnrén 真人) breathes through the heels whereas the ordinary man breathes through the throat”. A study by Ishida Hidemi (1988) shows that zhongxi designated in antiquity one of four kinds of breathing: through the skin, through the nose and mouth, through the throat (to absorb the celestial breath), and through the heels (to absorb the earthly breath).”—Catherine Despeux

“From the Song period (960-1270), under the influence of neidan, zhongxi also refers to the circulation of the inner energies that descend to the heels and then rise from the yŏngquán 湧泉 point, located in the middle of the sole of the foot, to the top of the head.”—Catherine Despeux

As always I have put tones in Pinyin; I feel myself better that way.