When I began training last year for my first marathon, my running partner Dave Freedholm, an experienced amateur distance runner, impressed on me the need to vigilantly avoid dehydration. His drink of choice was Accelerade. Like Gatorade, the original sports drink, it's packed with sugars and sodium to provide energy and replace the electrolytes depleted in sweat. But it also contains protein, which he said would help my muscles repair themselves more quickly after the punishing training runs he took me on.
Sure enough, I never felt much pain until after the marathon itself, and even then I recovered within a couple of days...