Osbdlhtwoatt is an acronym meaning; "Only small boys don't like having to work out all the time". It is commonly used in a joking manner among professional gymnasts when their workout partner or friend wants to skip leg day, or arm day or any day really.
Jim: Wanna go to the gym?
Freddy: I'm not really feeling up to it today. I'll stay home
Jim: Osbdlhtwoatt