system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do muscles look like they're permanently in a flexed position after working them out?

I've noticed this especially with my biceps, where after giving the a good work out, they look like they're perpetually flexed, and when I actually try to flex then, here isn't much difference.
gpt
When muscles are being used or anticipate being used, they fill up and engorge with blood. Same principle as a penis filling up with blood for an erection, after you work out your muscles fill up with blood to stay full.