Nutrition and running is a major issue; it causes much discussion and confusion even amongst the scientific community; one factor is likely that nutrition is individual. Someone running the GNR in 60 minutes is not going to require the same as someone running 4hours! So, where do you start and what do you need to consider?
First off how long is it going to take you; realistically! If 60 minutes then you very likely need nothing at all, your so well trained your going to give Mo Farah a run for his money, you will eat well and normally in the days leading up to the race and will likely taper your training so your body will re-stock its glycogen (energy) stores and you could run 2 marathons back to back!
Normally most are happy with close to 2 hours for the GNR. So if this is the case your going to burn at least 2000calories; good on you!! Your body can easily provide the fuel for this, depending on how well conditioned you are!! Even the leanest amongst us have enough energy stored to run 2 back to back marathons. But, if you hydrate and fuel you might just run faster, feel better and have a better day and subsequently recover faster for the after race party!!
You need to look at the race organisation and see what they might provide on the day during and after the race. Sometimes they provide simply water and or Coke or some other sports drink as well as energy gels. Find out so you can plan, you don’t want to have to carry anything if its available on the course itself, carrying extra weighs you down and makes running uncomfortable.
The key is your body can only absorb so much fluid and calories whilst exercising. This depends on your body, your size, your weight and muscle mass, sweat rates and fitness levels. Our bodies are well prepared for exercising for at least an hour without any need for nutrients. Sometimes if we have access to fluids and calories we take on too much and make ourselves sick, we often feel and perform much better with only small and frequent amounts of supplementation so again, going by ‘feel’ and instinct can be your best guide, listen to the body!
A good target for the 2hr runner is to start well rested having eaten and fed normally before the race, as you would for a long training run. Then aim to take a gel (120cal) every 5km with water or sports drink to wash it down. That should do it fine but you need not drink large amounts, if your stomach is sloshing around you have had too much!!
Whatever you plan on doing, you should have practiced it in training first.
Phil Smith, Sports Therapist