My guess is the clearing techniques should be absolutely popular now (not so popular like popularity itself though) but giving a kind of refreshment and a new start after swimming in the mass media 24/7 streaming. Some quotations from the second volume of encyclopedia look helpful.
“The idea of “nourishing” (yang) is prominent in Chinese thought: one can nourish life (yăngshēng 養生), the inner nature (yăngxìng 養性), the body (yăngxíng 養形), the whole person (yăngshēn 養身), the will (yăngzhì 養志), and the mind (yăngxīn 養心). The term yăngshēng 養生 designates techniques based on the essence, the inner or outer breath, and the spiritual force (jing, qi, shen); these techniques are grounded on physiological, psychological, and behavioral principles and include gymnastics (dăoyĭn 導引), massage, breathing (fuqi, xingqi), sexual hygiene (fángzhōng shū 房中書), diets (bigu), healing, meditation and visualization, and rules of daily behavior.”
“The term is first mentioned in Zhuangzi 3, a chapter entitled “Mastering in Nourishing Life” (“Yăngshēng zhŭ” 養生主).”–Catherine Despeux.
“The yangsheng practices flourished during the Han period. They are described in several Mawandui manuscripts dating to about 200 BCE, including the Hé yīnyáng 合陰陽 (Joining Yīn and Yáng), the Tiānxià zhìdào tán 天下至道談 (Discourse on the Ultimate Way Under Heaven), the Yăngshēng fāng 養生方 (Recipes for Nourishing Life), the Shíwèn 十問 (Ten Questions), and the Quègŭ shíqì 卻穀食氣 (Refraining from Cereals and Ingesting Breath; see translations in Harper 1998). These manuscripts give importance to sexual hygiene and to the ingestion of breath (see fuqi).”
“One of the most influential works of the time, preserved only in fragments, is the Yangsheng yaoji (Essentials of Nourishing Life) of Zhāng Zhàn 張湛 (early fourth century).”
“In the twentieth century, yăngshēng 養生 evolved into the modern science of wèishēng 衛生 (hygiene) on the one hand, and into qìgōng 氣功 on the other.”—Catherine Despeux.
Frankly, I don’t like the idea of recent separation of yăngshēng into wèishēng and qìgōng at all, I do would prefer to read the chapter “Mastering in Nourishing Life” (Yăngshēng zhŭ 養生主) in Zhuangzi soon after it has been done by the ancient author.