As early as in Huangdi Neijing, it was pointed out: "Yang exhaustion leads to lying down, while Yin exhaustion leads to fainting." Among the three magic weapons of ancient health preservation, "three chills and two downs, seven out of ten". "Two falls" means a good nap in the middle of the day.
The so-called "nap" means "sleeping at noon and taking a nap at noon".
From 23: 00 p.m. to early morning 1, when the yin is the most abundant and the yang is the weakest; At noon, it is 1 1 to 13, when the yang is strong and the yin is weak.
Noon and noon are the times when yin and yang alternate, and it is also the time when the body's menstrual qi "closes yin" and "closes yang". Sleeping at noon and noon every day is conducive to nourishing yin and strengthening yang.