There is a thread over on r/Showerthoughts where many have said the ancient Chinese army didn't care if the men they recruited were physically incapable of serving in the army, only needing one man per family as "fodder". Is this true? What if a family was not able to provide a suitable man?
I have insufficient knowledge of Chinese history and the armies of Antiquity to answer the question from those specific angles, but where it concerns the recruitment and mobilization of the common man in Europe in the Middle Ages, the physical condition was definitely of little concern.
I've written about the approximate of the levy system in parts of the Low Countries, the heervaart, before (which in a lot of aspects is comparable to the levy in other European domains, exceptions notwithstanding), but suffice it to say in this context that the military power of commoners from rural areas (farmers and/or peasants depending on the social-economic status) was lackluster, especially in comparison to the mobilized citizenry who not only often had a degree of military training as well as organization through the guilds, but also were financially in a better position to obtain armament, if at all necessary, as cities were in the habit of arming their own citizenry in times of external threats. Whether these citizens were also physically in a better state as some of their rural counterparts is difficult to conclude with certainty, but is doubtful. On some of the commoners mobilized by the heervaart in the County of Holland:
die cuyper van Voorschoten, een out, arm man ende manc aen beide ziden; een jonc knechtkin, hiet Jan ende is licht 14 jaer out ende daertoe arm of Gerrit Cleve, een arm man van Zoeterwoude ende is ghescoert/ghestoert
the cooper from Voorschoten, an old and poor man and with a limp on both sides; a young stableboy named Jan, barely fourteen years of age and therefore poor, or Gerrit Cleve, a poor man from Zoeterwoude, badly injured/mentally insane.
^(The last word depends on the quote. The former is used in Jansen & Hoppenbrouwers the latter in De Graaf.)
The extent to which the population mobilized in the rural parts of these lands were considered undependable at best is evident once we see that the counts and their deputies were often quite content with the commoners refusing mobilization, as that resulted in taxation (if they opted out before mobilization, with permission to do so) or fining (if they refused during mobilization) by the bailiffs, with the proceedings then used to hire proper soldeniers, mercenaries if you will.^(2)