Dr. Stellingwerff has researched the subject from a scientific approach and has significant field experience working with endurance athletes in a range of sports, and is an accomplished runner in his own right.
Here are the key points Dr. Stellingwerff makes in regards to nutrition for the marathon.
You will run out of glycogen by around mile 18 or between 90 to 120 minutes. Your body can store, at most, around 2000 calories of energy in the form of glycogen. No amount of carbo-loading will help you overcome this. And, if you run a marathon in your anaerobic zone, you are burning mostly carbohydrates and cannot utilize fat effectively. This is why the marathon is uniquely challenging – ultras generally remain aerobic so you can access fat stores more readily and shorter races aren’t long enough to run out of glycogen.
|Possibly too much all at one time:-)|
Target the rule of 15 – 15 g of carbohydrates, 150 mL of fluids every 15 minutes. Since each gram of carbohydrate delivers four calories, this is 240 calories per hour. Sports drinks typically provided at marathon aid stations contain around 14 grams of carbs per 230ml – this is not a concentrated enough form of carbohydrates and needs supplemented with energy gels. Gels typically provide 20 grams of carbohydrates per package.
- 1 150ml cup of sports drink - 10 grams of carbohydrates
- 1/4 pouch of gel to increase carbohydrate concentration - 5 grams of carbohydrates
The maximum fluids the stomach can absorb per hour is 700-800 mL. This is three cups of water or sports drink per hour. This also combines with the above point to limit the amount of calories per hour you can take in via carbohydrate and electrolyte drinks at ~200.
Combining the concepts above, one can begin to plot a fueling strategy for their race, considering the location of aid stations (often spaced every 1.5 miles – thus the 15 minute timing may be a bit tricky and due to these issues Dr. Stellingwerff advocates bringing your own fuel belt with sports drink and gels to supplement the aid stations on course.
- Having a gel bottle with four gels mixed with a small amount of water can be an easy way to increase carbohydrate concentrations at each aid station.
- If it is going to take 30 minutes to reach each aid station having sports drink as well as the gel flask on your fuel belt will allow you to maintain hydration every 15 minutes.
- If it is going to take 15 to 20 minutes to reach aid station you will not need to carry sports drink but having a gel flask with you can still be valuable to increase the carbohydrate concentration.
Next up ultra marathon fuelling strategy.