It will do nothing for an endurance sport at all..In fact the extra water you retain will make endurance activities harder. It helps only with explosive movements lasting 5-15 seconds. It retards lactic acid build up and will add a rep or two to your strenght. It does not give you energy so to speak rather a boost of power- one could say energy in as much as an extra rep or 10-15 lbs of power very quickly is concerned. Sports such as shot putting, power lifting, some foot ball positions would benefit.  Loading is not necessary, thats only a way for the marketers to make money. It makes the muscles seem fuller and thicker.