Great question Dan. I will try to be a bit careful with my answer, knowing there is a wide range of potential readers hoping to find a solution to their particular issues. It is important to realize that works for you might not work for your neighbour or training partner, based on your physiologic differences, your past experience, and your own history of training and structural development.
The simple answer is, carry your fuel, collect water at the aid stations. This is the lighter and more efficient version of the "carry EVERYTHING you are going to consume" rule.
As was demonstrated over the past two weeks at events from Utah to Salmon Arm, even some of our most experienced and well-trained athletes have not quite figured it ALL out yet, and I am going to take a modicum of responsibility for not being clear enough with some of them before their races. There are a couple of key points that NEED to be remembered on race day:
1) What you have PLANNED to eat, is not necessarily what you will NEED to eat on race day.
2) What you WANT to consume in terms of caloric intake/hour might not be what you are ABLE to consume.
3) The INTENSITY of the exercise will affect your ability to ABSORB nutrients form your stomach and intestines.
4) The solution to most episodes of low energy in long races is most often a shortage of FUEL, or a problem with pacing. The fuel issue can be dealt with on site as soon as the problem is recognized, whereas the pacing issue is a learning experience that can only be corrected in the future.
5) The two main causes of stomach "cramping" are residual fuel left in the stomach which has yet to be absorbed, or pain secondary to diaphragm weakness. Again, the issue of bloating and true stomach "cramping" (as opposed to diaphragm pain) can be dealt with almost always by simple dilution with large volumes (500ml-1,000ml) of pure water. The diaphragm issue needs rest, recovery, and appropriate training for future events.
So, given that advice, both Ginny and I have slightly different approaches to our race day nutrition, and both of us have been successful with our own plan. I take ALL my calories as either e-load, e-mend, or e-fly, with a combination of each. Depending on the heat expected, I also add e-discs and salt tabs to this mix to help replace the sodium and other salts lost in the sweat. I combine these mixtures into a very concentrated mixture in my bottles, knowing that I will need to collect adequate amounts of water to help with digestion and hydration. I supplement these calories with a number of gels, which are also easy to carry and consume en route. The aid stations provide everything else I need, which is primarily water, and the occasional "treat", like a half banana, energy bar or chocolate bar if the craving hits me. In fact at Ironman Wisconsin, the only items I took from the aid stations were 4 bottles of water, which were consumed through the roughly 5 1/4 hours I spent on the bike. In New Zealand, I was really grateful for a banana and three small Snickers bars that were handed out on the final aid station
The run will bring you even less ability to absorb nutrients, so a careful intake of calories will really depend on your own personal tolerance and the intensity you plan to run. I alternate between water and coke/gels through the marathon, and have never had any stomach issues. But I recognize this is not the case for everyone.
All the best, bring back your reports from your experiments, and let us know how it goes.
