《上古天真》篇曰∶上古之人，其知道者，法于阴阳，和于术数，（知道，谓知修养之道也。夫阴阳者，
天地之常道。术数者，保生之大论。故修养者，必谨先之。）食饮有节，起居有常，不妄作劳，（食饮者，
充虚之滋味；起居者，动止之纲纪。饮食自倍，肠胃乃伤。《生气通天论》曰∶起居如惊，神气乃浮。是恶
妄动也。广成子曰∶必静必清，无劳汝形，无摇汝精，乃可以长生。所以圣人先之也。）故能形与神
俱，而尽终其天年，度百岁乃去。（形与神俱，同臻寿分，谨于修养，以奉天真，故尽得终其天年。去，
谓去离形骸也。《灵枢经》曰∶人生百岁，五脏皆虚，神气皆去，形骸独居而终矣。）今时之人不然也，（离于
道也。）以酒为浆，（溺于饮也。）以妄为常，（寡于信也。）醉以入房，（过于色也。）以欲竭其精，以耗
散其真，（乐色曰欲，轻用曰耗，不节则精竭，轻用不止则真散。是以圣人爱精重施，髓满骨坚。）不知持满，
不时御神，（言轻用而纵欲也，爱精保神，如持盈满之器，不慎而动，则倾竭天真，吾形有神，不时时御之。）务
快其心，逆于生乐，（快于心欲之用，则逆养生之乐矣。）起居无节，故半百而衰也。（离于道则寿不
能终尽于天年矣。）上古圣人之教下也，虚邪贼风，避之有时；恬淡虚无，真气从之，精
神内守，病安从来。（邪乘虚入，是谓虚邪，最害中和，谓之贼风。《灵枢》曰∶邪气不能独伤人，人虚乃邪
胜之也。恬淡虚无，法道清静，精气内持，故其虚邪不能为害也。）是以志闲而少欲，心安而不惧，形
劳而不倦，（内机息，故少欲，外纷静，故心安，起居皆适，故不倦也。）气从以顺，各从其欲，皆得
所愿。（志不贪，故所欲皆顺；心易足，故所愿必从；不异求，故无难得也。《老子》曰∶知足不辱，知止不殆，
可以长久。）是以嗜欲不能劳其目，淫邪不能惑
其心。（《老子》曰∶不见可欲，使心不乱。又曰∶圣人为腹不为目。）所以能年皆度百岁，而动作不衰
者，以其德全不危也。（《庄子》曰∶执道者德全，德全者形全，形全者圣人之道也。）女子七岁，肾气
盛，齿更发长。（老阳之数极于九，少阳之数次于七，女子为少阴之气，故以少阳数偶之，明阴阳气和，乃能
生成其形体，故七岁肾气盛，齿更发长。）二七而天癸至，任脉通、太冲脉盛，月事以时下，故
有子。（癸谓壬癸，北方水干名也。任脉、冲脉，皆奇经脉也。肾气全盛，冲任流通，经血渐盈，应时而下，天
真之气降，与之从事，故云天癸也。然冲为血海，任主胞胎，二者相资，故能有子。谓之月事者，平和之气，以
三旬而一见也。）三七肾气平均，故真牙生而长极。（真牙，谓牙之最后生者，肾气平而真牙生者，表牙
齿为骨之余也。）四七筋骨坚，发长极，身体盛壮。（女子天癸之数，七七而终，年居四七，材力之半，
故身体盛壮，长极于斯。）五七阳明脉衰，面始焦，发始堕。（阳明之脉气营于面，故其衰也，发堕面焦。）六
七三阳脉衰于上，面皆焦，发始白。（三阳之脉，尽上于头，故三阳衰，则面焦发白。所以衰者，妇
人有余于气，不足于血，以其经月数泄脱之故。）七七任脉虚，太冲脉衰少，天癸竭，地道不通，
故形坏而无子也。（经水绝止，是为地道不通，冲任衰微，故形坏而无子。）丈夫八岁肾气实，发长齿
更。（老阴之数极于十，少阴之数次于八，男子为少阳之气，故以少阴数合之。《易系辞》曰∶天九地十，则其数
也。）二八肾气盛，天癸至，精气溢泻，阴阳和，故能有子。（男女有阴阳之质不同，天癸则精血
之形亦异，阴静海满而去血，阳动应合而泄精，二者通和，故能有子。《易系辞》曰∶男女媾精，万物化生。）三
八肾气平均，筋骨劲强，故真牙生而长极。四八筋骨隆盛，肌肉壮满。（丈夫天癸八八而终，
年居四八，亦材力之半也。）五八肾气衰，发堕齿槁。（肾主骨，齿为骨余，肾气既衰，精无所养，以故发
堕齿槁。）六八阳气衰竭于上，面焦发鬓颁白。（阳气，阳明之气也。足阳明脉起于鼻，侠口环唇，交承
浆，上耳前，至额颅，故衰于上，则面焦发鬓白也。）七八肝气衰，筋不能动，天癸竭，精少，肾脏衰，
形体皆极。（肝气养筋，肝衰筋不能动，肾气养骨，肾衰形体疲极，天癸已竭，故精少也。）八八则齿发
去。（阳气竭，精气衰，故齿发不坚，离形骸矣。）肾者主水，受五脏六腑之精而藏之，故五脏盛，乃能
泻。（五脏六腑，精气淫溢，而渗灌于肾，肾乃受而藏之，非肾一脏而独有精，故曰五脏盛乃能泻。）
今五脏皆衰，筋骨解堕，天癸尽矣。发鬓白，身体重，行步不正，而无子耳。（物壮则老，谓之天道也。）
有其年已老而有子者，此其天寿过度，气脉常通，而肾气有余也，（禀天真之气有余也。）此虽有子，男不
过尽八八，女不过尽七七，而天地之精气皆竭矣。（虽老而生子，子寿亦不能过天癸之数。）
《上古天真论》篇中说：上古时代的人，那些懂得养生之道的人，效法阴阳变化的规律，调和各种养生方法，（所谓“知道”，是指知晓修养身心的道理。阴阳是天地运行的永恒法则；术数是保养生命的根本理论。所以修养身心的人，必须首先谨慎地遵循这些原则。）饮食有节制，起居有常规，不胡乱过度劳累，（饮食是用来填补空虚、提供滋味的；起居是行动和静止的纲纪。如果饮食过量一倍，肠胃就会受伤。《生气通天论》说：起居受到惊扰，神气就会浮越。这是厌恶妄动的原因。广成子说：一定要清静，不要使形体劳累，不要动摇你的精气，这样就可以长生不老。所以圣人先做到这一点。）因此能够形体与精神协调统一，从而享尽自然的寿命，活到一百岁才离世。（形与神俱，指共同达到寿数的极限，谨慎地进行修养，以顺应天真之气，所以能完全享尽天年。“去”，是指离开形体骸骨。《灵枢经》说：人活到百岁，五脏都虚弱了，神气都离开了，只剩下骸骨独自存在而终结。）
现在的人却不是这样，（背离了大道。）把酒当作浆水一样随意饮用，（沉溺于饮酒。）把妄为当作常态，（缺乏诚信/信守正道。）醉酒后行房事，（纵欲过度。）因为欲望而耗竭精气，因为放纵而散失真气，（追求声色之乐叫作“欲”，轻率使用叫作“耗”，如果不加节制就会精竭，轻率使用不止就会真散。因此圣人爱惜精气，慎重施泄，使骨髓充满，骨骼坚固。）不知道保持精气的充盈，不能适时地调摄精神，（意思是轻率使用且放纵欲望，爱护精气、保护神气，就像拿着装满水的容器，不小心晃动，就会倾覆枯竭天真之气，我们的身体有神，需要时时驾驭它。）只图一时的心意畅快，违背了养生的乐趣，（在心意欲望的使用上感到痛快，就违背了养生的快乐了。）起居没有节制，所以不到五十岁就衰老了。（背离了大道，寿命就不能享尽天年。）
上古圣人对百姓的教诲是：对于虚邪贼风等致病因素，要按时避开；心境恬淡虚无，真气就能顺从，精神内守，疾病从哪里产生呢？（邪气趁虚而入，叫做虚邪，最伤害中和之气，称为贼风。《灵枢》说：邪气不能单独伤人，人气虚弱时邪气才能战胜人体。恬淡虚无，效法道的清静，精气在内持守，所以虚邪不能为害。）因此意志闲适而欲望少，内心安定而不恐惧，形体劳作但不疲倦，（内心机巧止息，所以欲望少；外界纷扰平静，所以心安；起居适宜，所以不疲倦。）气机随之顺畅，各随其愿，都能实现愿望。（志向不贪婪，所以想要的都能顺遂；心境容易满足，所以所愿必得；不追求奇异之物，所以没有什么难得到的。《老子》说：知足就不会受辱，知止就不会危险，可以长久。）因此嗜欲不能劳损他的眼睛，淫邪不能迷惑他的心。（《老子》说：不看引起欲望的事物，使心不乱。又说：圣人只求温饱而不逐目之欲。）之所以能都活到百岁，动作依然不衰老，是因为他们的道德完备，不受危害。（《庄子》说：执守大道的人道德完备，道德完备的人形体完备，形体完备的人是圣人的道。）
女子七岁时，肾气旺盛，牙齿更换，头发生长。（老阳之数极于九，少阳之数次于七，女子属少阴之气，所以用少阳数与之相配，说明阴阳气和，才能生成形体，所以七岁肾气盛，换牙长发。）十四岁时，天癸到来，任脉通畅，太冲脉旺盛，月经按时来潮，所以能生育。（“癸”指壬癸，北方天干之名。任脉、冲脉，都是奇经八脉。肾气全盛，冲任流通，经血逐渐充盈，应时而下，天真之气下降，与之配合，所以叫天癸。然而冲脉为血海，任脉主胞胎，二者相互资助，所以能生育。称为月事，是因为平和之气，大约三十天出现一次。）二十一岁时，肾气平和，智齿长出，身体发育达到极点。（真牙，指最后长出的牙齿，肾气平和则真牙生出，表明牙齿是骨之余。）二十八岁时，筋骨坚硬，头发长到极点，身体最为壮盛。（女子天癸的周期以七七四十九岁结束，处于四七二十八岁时，体力精力的一半，所以身体壮盛，发育达到极点。）三十五岁时，阳明脉开始衰退，面部开始憔悴，头发开始脱落。（阳明经脉的气血营养面部，所以衰退时，头发脱落，面部憔悴。）四十二岁时，三阳脉在头部开始衰退，面部全面憔悴，头发开始变白。（三阳经脉，全部上行至头，所以三阳衰退，则面部憔悴，头发变白。之所以衰退，是因为妇女气有余而血不足，因为每月月经流失的缘故。）四十九岁时，任脉虚衰，太冲脉衰少，天癸枯竭，月经停止，所以形体衰老而不能生育。（经水绝止，这叫地道不通，冲任衰微，所以形体衰老而不能生育。）
男子八岁时，肾气充实，头发生长，牙齿更换。（老阴之数极于十，少阴之数次于八，男子属少阳之气，所以用少阴数与之相合。《易系辞》说：天九地十，就是这个数。）十六岁时，肾气旺盛，天癸到来，精气满溢而泻出，阴阳调和，所以能生育。（男女有阴阳体质的不同，天癸作为精血的形态也各异，阴静海满而去血，阳动应合而泄精，二者通和，所以能生育。《易系辞》说：男女媾精，万物化生。）二十四岁时，肾气平和，筋骨强劲有力，智齿长出，身体发育达到极点。三十二岁时，筋骨隆盛，肌肉丰满壮实。（男子天癸的周期以八八六十四岁结束，处于四八三十二岁时，也是体力精力的一半。）四十岁时，肾气开始衰退，头发脱落，牙齿枯槁。（肾主骨，齿为骨之余，肾气既衰，精无所养，所以头发脱落，牙齿枯槁。）四十八岁时，阳气在头部衰竭，面部憔悴，两鬓斑白。（阳气，指阳明之气。足阳明脉起于鼻旁，夹口环唇，交承浆穴，上行至耳前，到达额颅，所以在上部衰退，则面部憔悴，两鬓白发。）五十六岁时，肝气衰退，筋脉活动不利，天癸枯竭，精液减少，肾脏衰退，形体极度疲乏。（肝气滋养筋脉，肝衰则筋不能动，肾气滋养骨骼，肾衰则形体疲极，天癸已竭，所以精少。）六十四岁时，牙齿头发脱落。（阳气竭，精气衰，所以牙齿头发不坚固，离开形体了。）
肾主水，接受五脏六腑的精气并贮藏它，所以五脏旺盛，肾才能排泄精气。（五脏六腑的精气淫溢，渗入灌注于肾，肾才接受并贮藏它，并非只有肾一脏独有精气，所以说五脏盛乃能泻。）现在五脏都衰退了，筋骨松弛下垂，天癸耗尽。头发两鬓变白，身体沉重，行走不稳，而不能生育了。（事物过于强盛就会衰老，这叫做天道。）
有的人虽然年纪大了却还有子女，这是因为他们天赋寿命超过常人，气脉常通，而肾气有余。（禀赋的天真之气有余。）这样的人虽然有子女，但男子不超过六十四岁，女子不超过四十九岁，天地间的精气都枯竭了。（虽然年老生子，子女的寿命也不能超过天癸的周期数。）
The "Shanggu Tianzhen Lun" (Treatise on the Heavenly Origin of Antiquity) states: People in ancient times, those who understood the Dao, modeled themselves after Yin and Yang, harmonized with Shu Shu (methods and numbers for preserving life), had regulated diet and drinking, regular daily routines, and did not engage in reckless exertion. Therefore, they could maintain the unity of Form (Xing) and Spirit (Shen), thus completing their natural lifespan, living to a hundred years before passing away.
People today are different. They treat wine as if it were water, make recklessness their norm, have intercourse while drunk, exhaust their Jing (Essence) through desires, and dissipate their Zhen Qi (True Energy). They do not know how to maintain fullness, nor do they manage their Shen (Spirit) at appropriate times. They seek only immediate gratification, going against the joy of life preservation, and have irregular daily routines; thus, they begin to decline by half their age (around fifty).
The teachings of the ancient sages to the people were: Avoid empty evils and thieving winds when necessary; remain tranquil and void of artificial desires, so that Zhen Qi follows; keep the Jing and Shen guarded within, and how could disease arise? Thus, one's will is leisurely with few desires, the heart is peaceful without fear, the body labors but does not become fatigued, Qi flows smoothly, all wishes are fulfilled, and everything is obtained as desired. Therefore, sensual desires cannot weary the eyes, and licentiousness cannot confuse the mind. This is why they can all reach a hundred years of age and their movements remain vigorous; it is because their De (Virtue/Ethical Integrity) is complete and they are not endangered.
Regarding women: At seven sui (years old), Kidney Qi becomes abundant, teeth change, and hair grows. At fourteen sui, Tian Gui (Heavenly Water/Menstrual Essence) arrives, the Ren Mai (Conception Vessel) becomes unobstructed, and the Chong Mai (Penetrating Vessel) becomes prosperous; menstruation occurs regularly, enabling conception. At twenty-one sui, Kidney Qi is balanced, wisdom teeth grow, and physical development reaches its peak. At twenty-eight sui, sinews and bones are strong, hair reaches its maximum length, and the body is in robust health. At thirty-five sui, the Yangming Meridian begins to decline, the face starts to wither, and hair begins to fall out. At forty-two sui, the three Yang meridians decline above, the face completely withers, and hair begins to turn white. At forty-nine sui, the Ren Mai becomes deficient, the Chong Mai declines, Tian Gui is exhausted, the "earthly pathway" (menstruation) ceases, the form deteriorates, and childbearing ends.
Regarding men: At eight sui, Kidney Qi becomes solid, hair grows, and teeth change. At sixteen sui, Kidney Qi is abundant, Tian Gui arrives, Jing essence overflows and is discharged, Yin and Yang harmonize, enabling conception. At twenty-four sui, Kidney Qi is balanced, sinews and bones are powerful, wisdom teeth grow, and physical development reaches its peak. At thirty-two sui, sinews and bones are luxuriant, muscles are full and strong. At forty sui, Kidney Qi begins to decline, hair falls out, and teeth wither. At forty-eight sui, Yang Qi衰竭 (depletes) above, the face withers, and temples turn gray. At fifty-six sui, Liver Qi declines, sinews cannot move freely, Tian Gui is exhausted, Jing is scarce, Kidney Qi declines, and the entire form reaches exhaustion. At sixty-four sui, teeth and hair fall out.
The Kidney governs water and receives the essence of the five zang and six fu organs to store it; therefore, only when the five zang are abundant can the Kidney discharge essence. Now, when the five zang all decline, sinews and bones loosen, Tian Gui is exhausted, hair and temples turn white, the body feels heavy, walking is unsteady, and childbearing ceases.
There are those who are old yet still have children; this is due to excessive natural longevity, constant flow of Qi and vessels, and surplus Kidney Qi. However, even if such individuals have children, men do not exceed the limit of 8x8 (64 sui), and women do not exceed the limit of 7x7 (49 sui); the essence and Qi of Heaven and Earth are fully exhausted.