"Carb loading". A favorite expression of runners from all walks of life. We all know we need carbs, how to properly take them in is a little trickier. In order for our bodies to work optimally, we need to take in the same amount of energy that we just burned off. Carbohydrates basically become the stored energy that we use after depleting our aerobic system. When you do not take in enough carbs during training, pre-race or during you run the risk of losing the lean muscle tissue that you need to get through a marathon. There are many different types of carbs out there but the goal is to get the most bang for your buck.
Ideally, you should try to get in your big carbs 3-4 hours before an event. Research shows you should take in 5-12 g/kg (depending on the length of the event) but anything over 13 g/kg has no effect on endurance performance and may cause GI issues. When doing an event that lasts longer than 90 minutes, you may want to ingest 2-3% more carbohydrates pre-race than if you were doing a race that lasts under a hour.
Carbohydrates are very important during a race as well. Research has found a link between carbohydrate ingestion and central nervous system performance during high intensity activity. Your brain needs carbs for energy the same way your body does. When you don’t have enough you will begin to feel dizzy, fatigued and disoriented. When you start to feel this way you are already behind. Get in some carbs ASAP. During competition, liquid carbs are usually a better option because they are easier to take in and they can also provide some hydration.
When deciding on a carb to eat before or during the race there are a few things to take into consideration. First of all, NEVER try a new carb on race day. You need to experiment before hand. You should pick a carb that is low in fat, low in fiber and has a decent amount of protein. The source of your carb should include many different types (glucose, fructose, lactose) because each type uses a different digestive transmitter so it will digest faster.
The importance of protein is often ignored. When performing long distance and high intensity events, it is important to take in protein for muscle performance. Women typically oxidize more fats while men oxidize more protein during an event, meaning men need to take in more protein. If you are not getting in enough carbs, amino acids, the building blocks of protein, begin to oxidize and breakdown tissue. This would require more protein. Protein is most important after racing. While racing, you will naturally breakdown muscle tissue, this is why you need to begin taking in protein after racing.
Coleman, E. Nutrition for the Marathon and Beyond: Optimize your performance by proper fueling. Marathon & Beyond. Sept/Oct 2012. 88-101. Jeukendrup, A. Nutrition for Endurance Sports: Marathon, Triathlon and Road Cycling. Journal of Sports Science. 2011.29.(S1).S91-S99. Stellingwerff, T. Contemporary Nutrition Approaches to Optimize Elite Marathon Performance. International Journal of Sports Physiology and Performance. 2013.8.573-578.
Wardenaar, F et.al. Nutrient Intake and GI Complaints of Ultramarathon Runners. International Journal of Sports Nutrition and Exercise. 2015.
Elizabeth Brewer, SPT & Kathleen Leninger, PT, DPT, NY Custom PT & Performance