I did muaythai all last year and have been on and off since I was 18 I'm 27 now. Does that temporarily change your physique or..not permanet?

Looks are deceiving. You may not look out of shape in the everyday sense, but you are out of shape as a fighter. Being fighting fit is a whole different thing from just not looking out of shape.

When you do not training sufficiently AND regularly, your muscles are not maintained at the level where they can react quickly because the fast twitch muscles have not been maintained and your muscle memory is basically nonexistent.

Muscles come in 2 types: fast and slow twitch. The slow twitch is that bulky look you see on bodybuilders and responsible for the power to do the heavy lifting, but the fast twitch is not something that you can tell just from the look of the muscle. And it is the fast twitch muscles that is responsible for speed and allow your strikes to snap like a whip. Not only that, it is the muscle memory for your fast twitch muscles formed from long regular training that allows for the smoothness and efficiency of the movement.

idk what that is soo