For about a month now, I've been exploring the concept of eating to the clock. I've sampled every flavor of GU and Roctane, including the energy drink mixes. I've also been trying to get a better handle on hydration and electrolyte replacement, skills I sometimes get right and sometimes get terribly wrong. For short runs of under five hours or so, I can screw everything up and still do okay. Screw up on a fifty-miler could end my race early, though, so I need to learn this stuff.
Mike and Drew recommend 250 calories per hour, not counting energy drinks. I know my stomach can't handle that much gel but I've tried one gel (100 calories) every 40 minutes and done well with it. I can get the rest of the calories from boiled potatoes and such at the aid stations.
I've sampled every flavor of GU and Roctane and settled on "Just Plain" GU which has caffeine and "Strawberry Banana" GU which does not. I didn't get along with the Roctane at all, which is handy because it costs twice as much and has a bunch of extra ingredients which I'm not sure about. When I'm hungry, I need maltodextrin and fructose; not maltodextrin, fructose, and orthanine alpha-ketoglutarate, whatever that is. I won't be able to test my nutrition plan for a whole twelve hours which is the goal I've set for the Heartland race, but I'm guessing that 360mg of caffeine (20mg x 18 gels) will be too much. I'm planning to carry four hours worth of the Strawberry Banana at the start and refill with Just Plain at the aid stations that allow drop bags.
I liked the GU Electrolyte Brew drink mix for one of my two water bottles. On my Tyson Parkway runs, I even practiced dumping the powder into an empty bottle before arriving at the "aid station" to save time. I practiced stowing the empty packets. In the end, though, I decided it was too much hassle. I can get the calories from gels and food and the electrolytes from pills and gels (which contain 50mg of sodium). Besides, I've discovered I really like the taste of plain water.
I'd been using Endurolytes which contain a fairly small amount of sodium but also have calcium, magnesium, potassium, vitamin B-6, and manganese. Some people have great luck with Endurolytes but my results were hit-and-miss. Sometimes I'd eat them like candy and still get cramps. I attributed the cramping not to electrolyte imbalance but to the fact that I was pushing out really long runs for for a relatively new runner. After a while, though, that explanation just didn't work any more. Today I switched to S!Caps which have a crapload of sodium (341mg), some potassium, and nothing else. I took one per hour and demolished my PR for three laps of Fayetteville Lake without even an inkling of cramping. I felt much better.
The other advantage of using the S!Caps alone rather than suplementing with an energy drink is that I can adjust my water intake and sodium intake completely separately. I've had the best luck drinking to thirst rather than trying to drink a certain amount per hour. A few weeks ago when I was experimenting with the electrolyte drink mixes, I drank too much and jacked my system up for three days. I left work early one day and missed a Wednesday speed workout because of it. I will never do that again.