Quote: mark_m "Can someone explain what all this 'bulking up' is? A player will have an optimum playing weight, any weight above that will be to their detriment.'"
As you say it is when a player is below his optimum playing weight and he needs to increase his muscle mass to attain the desired weight that has been requested of him. I remember taking to S&C coach of a super league side who the club had given a player 6 months to put an agreed weight on without increasing his fat percentage, and if he didn't his contract would not be renewed, as he was too lightweight to be prop and too heavy for anywhere else.