Why does this happen?

[Anonymous]

Hi,
So I have always been naturally skinny. And every month or so, I get the motivation and workout for a week or so, which fades lately.
But as soon as I do workout, like a day or two later, I really see some definition in my abdomen, like abs.
Now I know I cannot possibly get muscle after a day of workout, but I swear to God that it happens every time I start working out, a day later.
Is this normal and does this happen to anyone else?

[Impalitteri]

Yes, this definitely sounds like swelling/inflammation from the workout. Lactic acid builds out causing the swelling. Working out also stimulates blood flow, increased blood flow causes the appearance of swelling.

[nestokyo]

it's definitely muscle growing or muscle swelling, it's definitely not a weight gain I promise lol, if ur overly skinny and you randomly work out even if it's a small workout sometimes u gain muscle or it swells or tenses up temporarily