[[Note that “youthful” does not necessarily mean between 18 and 22!]]
Everything is relative
Methusula was still ‘youthful’ at about 850 years old
Joshua 14: 10“Now then, just as the Lord promised, he has kept me alive for forty-five years since the time he said this to Moses, while Israel moved about in the wilderness. So here I am today, eighty-five years old! 11I am still as strong today as the day Moses sent me out; I’m just as vigorous to go out to battle now as I was then. 12Now give me this hill country that the Lord promised me that day. You yourself heard then that the Anakites were there and their cities were large and fortified, but, the Lord helping me, I will drive them out just as he said.” 13Then Joshua blessed Caleb son of Jephunneh and gave him Hebron as his inheritance.
Paraphrased:
Yeah, I'm 85 years old!
Now give me the hill country so I can kick some Anakite a--!