Is it normal for, when you flex, your upper abdomen to extend

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Is it normal for, when you flex, your upper abdomen to extend past your lower abdomen?

I don't really have a pic that shows what I mean but, when I flex my abs do not look like some flat board like I see all the models have. I know that I'm not supposed to care about how the models look, but I mean, I have a fucked up digestive system*, so I'm curious if this is related.

*I have a mild version of hirschsprungs disease. I have had chronic constipation for as long as I can remember. I never got the surgery as a baby (I will when I'm an old geezer, not looking forward to it) but i'm not talking out of my ass here, it's a doctor-confirmed thing, and genetic in my family. I wouldn't know what hirschsprungs is otherwise.

Pic related is my best pic of me flexing. I'm 5'7, 148-150 lbs, and I'm 18 so you get to see teenage acne sorry