I have a Question about superman and any other super hero that cant be hurt

So according to biology of the body and how the Muscles work in order to GROW and to become "ripped" they need to GET HURT that why when we go to the gym and we do a very good workout the next day our muscle in that area (chest/back/arms/legs/etc) are sore and that why we dont train them 2 days in the row because we give them a time to heal and recover!

So with the hurting and healing/recovery the muscle grows bigger and that how we create a ripped body that well known to everyone

So my Question here how Superman that he cant be hurt and his body cant get hurt unless he gets hit by something very very very strong ( i mean the dude can tank multi super novas and stuff) so how he have A ripped body? because if he cant be hurt it mean that his muscle should have been normal and never grow because they never get hurt so the fibre of the muscle never heal to go into recovery and actually grow

So If you think about it SUPERMAN should be ripped or any other super hero that cant be hurt they should have beed normal guys

And because they dont need food and their body cant hurt so anything they eat it become insta Energy so it cant be fat ether

So the people who create super heros always tend to forget how the muscles actually work

Unless there is a comic on superman story that actually explain how he got ripped then cool that why i ask here if anyone knows because i know that many people here see anime read comics and stuff