When planing your nutrition plan for your upcoming half marathon or marathon aim too drink frequently, drinking 150ml of sports drink every 15 to 20 minutes. The sports drinks provides a portion of your required carbohydrates and the electrolytes you need to avoid cramping.
If you are using the aid stations it is a good idea to grab a cup of water as you enter the aid station and a cup of sports drink as you exit. Since you’ll undoubtedly spill some just grabbing the cup, you’ll now have a good chance of getting the 150ml you want. Be patient in the aid stations and don’t just gulp the fluid and toss the cup. Crimp the top of the cup and run with it as you drink. Then, grab the second cup and do the same.
Over and above this, as you will not receive all the carbohydrates you need from sports drink alone, I would suggest carrying a small gel flask with four gels mixed with water and sip on this though the race or better yet take a swig of gel as you approach each aid station, grab a cup of water as you enter the aid station to wash down and then a cup of sports drink as you exit. This way you receive the fluids, carbohydrates and electrolytes you need to fuel your body for the entire event.
I believe by following this strategy you will maintain your blood sugar levels, have energy for your working muscles and help restock your energy stores for afterwards. Compared to drinking just water for the duration of the marathon I feel it also helps in post marathon recovery, so you can be back on the roads training again with minimal loss of fitness.
Simple Race Plan
Detailed Race Plan
Overall the best strategy is to complete your prerace meal with 300-400 calories of complex carbohydrates and a little protein 3 hours before event to allow time for digestion so that you can push harder and feel great.
But, there is no need to sacrifice critical sleep just to squeeze in a meal if you need a few more hours of rest. If you begin fueling 10-20 minutes after the start of your event, your performance will not suffer.
Being hungry before you exercise won't hurt performance. If you must eat something, about 10 minutes before the start consume 100 calories of a nutrient-dense fuel such as a gel.
The night before an event, eat light and clean with no refined sugar, saturated fats, or alcohol. Eat until you are satisfied and no more.
For maximum glycogen replenishment, consume 30-60 grams of quality complex carbohydrates and 10-20 grams of protein as soon as possible after your event.
Detailed information on how to apply Dr Trent Stellingwerff's Rule of 15 to your specific race nutrition needs with 15 grams of carbohydrates every 15 minutes with 150ml of fluids.
Hope this helps and good luck in your upcoming marathon!