"Going on tour is like getting married. You have to look your best and prepare by exercising three to five times a week.
"If we're touring and doing show after show, we have to really look after ourselves. We might occasionally have a few drinks in the dressing room, but we can't really do that.
"I'm sure most of the time we'll be back in our hotel rooms, relaxing in the bath, because we can't go out and play!"
As well as limiting the girls' alcohol consumption, Mel is also going to make sure the group get an early night before each show and eat the right foods.
She added: "We'll be going to bed by 10.30am. When you have a show, the night before has to be an early one.
"You should eat about four hours before so you're not hungry when you go on stage and have the energy needed to perform. I also recommend avoiding dairy because it can affect your voice."