well protein shakes aren't really nescessary(sp) unless your doing weight training. they do have carbs in them to help you keep going, but the idea is that when doing heavy weight training you will actually slightly tear your muscles (thats why it hurts so much a couple of days after) and you drink the protein shake to get the big hit of protein in which is used to repair these tears with extra muscle, thus bulking the muscles up. thats why you will find body builders and strong men and people who use weights a lot will eat a high protein diet as well as have their protein shakes. if your just looking to increase your stamina or something then just stick with a high protein meal with carbs like Bob suggested and drink lots of fluids, preferably isotonic (lucosade/powerade etc.) and just keep going. but if you want to do weights as well then you may want to look into shakes. buy a copy of muscle and fitness and have a read through that, there is always something to do with nutrition in there and also look on the net for info about nutrition based on the kind of training you will be doing.