Aerobic endurance is classed as the ability to exercise for long periods of time with the absence of fatigue. Therefore, it is important that athletes train and prepare appropriately for the demands of their event. This may be through the intensity or the volume of training.
In terms of nutrition prior the event itself; all endurance athletes should put a focus on carbohydrate nutrition, whatever the type or format of endurance event they take part in. Ultimately, the goal from consuming carbohydrates is the same – provide energy to fuel performance.
This article will provide you with a guide as to how to fuel yourself appropriately, directly before and during an endurance competition/event and give you an insight in to the benefits of carbohydrates on performance.
The body utilises carbohydrates more effectively than fat as a fuel source. When we metabolise fat through respiration, we generate 4.7 Kcal of energy per litre of oxygen consumed. However, when we metabolise carbohydrates, we generate 5.05 Kcal of energy per litre of oxygen consumed (Krogh & Lindhard, 1920). This means that as a fuel source for performance, carbohydrates are the best for providing large amounts of energy to fuel muscle contraction and subsequently, fuel performance.
The intensity and pace in modern endurance events such as tour cycling or marathons is so great, that if these athletes exercised at these intensities for any more than 2 hours, they would deplete their glycogen stores completely (Hawley et al, 1997). So any endurance athlete needs to prepare appropriate nutrition intervals where they re-fuel their glycogen stores to allow the continuation of performances at such intensities.
The Myth about Fats
Everyone assumes that when we exercise for a long period of time, we predominantly oxidise fats as a fuel source. This is not the case. For example, when professional athletes run in a marathon, 75% of their energy sources will come from glycogen which is the stored form of glucose (the main carbohydrate we use to generate energy). Only 20% of energy will be generated from fats (Costill et al 1971). More recent research by Spriet et al (2007) suggests it is even possible that professional marathon runners can complete the event using only carbohydrates as a fuel source. Therefore, it is crucial to ensure that endurance athletes are appropriately fed and fuelled for such events due to the demands on glycogen stores the events has.
The research paints a very clear picture. Karlsson & Saltin (1971) found that a high carbohydrate meal prior to a 30km run significantly improved the runners time for the event. So to improve performance, we need more carbohydrates.
Carbohydrate Loading – Prior to Performance
Carbohydrate loading is a great technique to ensure glycogen stores are at their max prior to the event. Based on research, our advice for carbohydrate loading would be to consume 5g/kg.bm 6 to 3 days before the event and 8-12g.kg.bm of carbohydrates 3 to 1 day before the event whilst reducing your training load to light sessions.
Type of Carbohydrate Supplements – During Performance
Within the event, we suggest you take the supplements immediately before, and if your event permits it, every hour to an hour and a half. This will ensure your glycogen stores remain at a good level.
Energy gels are easy to carry on you and are ideal to consume during and after most types of sports. Simply consume on their own during or after your race for a refreshing burst of flavour and energy. Each gel provides 24g carbohydrates from a combination of Maltodextrin and Waxy Maize Starch, which also means it is low in sugar.
Alternatively, you could use carbohydrate powders.
As a general consensus for what you should be doing for an endurance event, we have simplified it into a few key points:
- Carbohydrate load effectively whilst reducing training load up to 6 days before.
- Look for carbohydrate gels and drinks for convienience.
- In the event, it could be beneficial to take supplements every hour to an hour and a half.
Costill, D.L., Branam, G., Eddy, D. and Sparks, K., 1971. Determinants of marathon running success. Internationale Zeitschrift für angewandte Physiologie einschliesslich Arbeitsphysiologie, 29(3), pp.249-254.
Hawley, J.A., Palmer, G.S. and Noakes, T.D., 1997. Effects of 3 days of carbohydrate supplementation on muscle glycogen content and utilisation during a 1-h cycling performance. European journal of applied physiology and occupational physiology, 75(5), pp.407-412.
Karlsson, J. and Saltin, B., 1971. Diet, muscle glycogen, and endurance performance. Journal of applied physiology, 31(2), pp.203-206.
Krogh, A. and Lindhard, J., 1920. The relative value of fat and carbohydrate as sources of muscular energy: with appendices on the correlation between standard metabolism and the respiratory quotient during rest and work. Biochemical Journal, 14(3-4), p.290.
Spriet, L.L., 2007. Regulation of substrate use during the marathon. Sports Medicine, 37(4-5), pp.332-336.
About the Author
Connor Stead and Andrew Triggs are Sport and Exercise Science students who write about training, nutrition and supplementation in exercise. Their background in sport comes mainly from football where they coach and compete at university level. More recently, they have started giving training and nutritional advice through Instagram (@trainingwithscience).