Astanga Hrudaya
वयस्त्वाषोडशाद्वालं तत्र धात्विन्द्रियौजसाम्। वृद्धिरासप्ततेर्मध्यं तत्रावृद्धिः परं क्षयः॥१०५॥
Vayah – age: The period up to sixteen years of age is balya (childhood) in which there occurs the increase of dhatu (tissues), indriya (sense, perception) and ojas (essence of tissues responsible for strength); the period up to seventy years in madhya (middle age, youth) in which there is no increase of tissues etc; after seventy years it is ksaya — decrease / depletion of tissues etc., or old age.
english translation
vayastvASoDazAdvAlaM tatra dhAtvindriyaujasAm। vRddhirAsaptatermadhyaM tatrAvRddhiH paraM kSayaH॥105॥
hk transliteration by Sanscript