okok i had a general answer but i conscripted the help of 310mc so this answer is Super long hehe

most we know is think from observation... midori can be assumed to be greater than average physical strength! some of it comes from his physical stature, but he also grew up working as a greengrocer. he's seen carrying really heavy boxes of vegetables (often multiple at a time, definitely more than an ordinary person can handle), and he's also capable of carrying kanata as a first year (despite being pretty heavy), and can carry things like TV monitors no problem, and can carry his unitmates on his shoulders too. there's also a scene where he carries a ladder while shinobus still on it and shinobus like HOW IS THIS SO EASY FOR YOU

but as for stamina, that's where he lacks. he gets exhausted pretty easily, especially compared to those more sporty like chiaki and tetora. he struggles with stuff like muscle training because of this

as for sports; he is in the basketball club, but he is not all too good at it... most of it is because despite being the perfect stature for basketball when he joined the club he was an Absolute beginner. even during his 2nd year he was still only good at the basics. he's fairly good at being defense though because his size helps him a lot (with chiaki coining his ability as the takamine barricade). Flowers of the Wasteland makes for a good measure of how good he is at basketball! and any other basketball club story too

but being in the club and ryuseitai did help him with his physical strength even more! as of his 3rd year in yumenosaki we don't know exactly how he's doing strength wise, but he's been gradually improving throughout the years!