Because my arms hurt, and you're standing up
Yes, it's true - my arms are killing me today, the near-aborted lovechild of my terrible state of fitness and my gung-ho-ness in the gym at the spa resort I went to on my honey(hiney?)moon.
A friend of mine has an excellent little quip prominently displayed in his room: "Pain is weakness leaving the body". If this is true, I expect to be benching your fat-ass mama by the end of the week. Just one rep, though, cos the bitch is heavy.