Carbo-loading: What? Why? How?
What?
Energy in the muscle and liver is stored in the form of glycogen, a type of long-chained glucose. Thus carbohydrate loading is a process of increased carbohydrate intake to load the muscles and liver to maximise energy storage.
Why?
Performance of course! Firstly, even in an 80km ultramarathon, up to 40% of energy uptake is from the various glycogen pathways (1). In a race, where access to additional energy intake may be out of one's control, it is important to maximise energy storage from the get go. Carbo-loading has been shown to increase time to exhaustion in endurance exercises lasting over 90 minutes and improve performance over a set distance (2). It has also been shown to improve performace during short high intensity bout of exercise (3). In simpler terms, carbo-loading allows you to run faster for longer.
How?
Here we will look at three methods of carbo-loading that you may utilise in your sporting endeavours.
Catapult Method (4)
A 6 day protocol. The first stage (day 1 to 3) involves undertaking high intensity exercises followed by a high protein/fat and low carbohydrate diet. In the second stage (day 4 to 6), switch to a high carbohydrate diet (up to 8g per kg of bodyweight). The idea behind this method is to starve the body of glycogen (pulling the catapult) and then allowing the body to supercompensate for the lack of glycogen during the second stage (release!), thus increasing carbohydrate store.
3 Day Method (5)
The most widely practiced method of carbo-loading. Simply undertake a 3 days high carbohydrate diet (8 to 10g per kg of bodyweight) and taper activity level for a week before your race. Glycogen level in muscle has been shown to increase by up to 40% with this protocol.
1 Day Method (6)
A group of smart guys in Western Australia asked the question nobody has been asking. How much does glycogen level actually change between 1 day and 3 days of a high carbohydrate diet. The answer is, it doesn't! Thus we now have the 1 day carbo-loading protocol. A single day of high carbohydrate diet(10g per kg of bodyweight) is sufficient to bring your muscle glycogen level to the max.
Conclusion
Carbo-loading does not work for everyone. In particular women in general has been shown to have a duller response to the standard carbohydrate protocol and must increase total energy intake at the same time (7). Always take the chance to test out a protocol prior to actually using it. On the eve of an important race, it is best to stick to what has been tested and proven by yourself.
2. Hawley, J. A., Schabort, E. J., Noakes, T. D., & Dennis, S. C. (1997). Carbohydrate loading and exercise performance. Sports Medicine, 24(2): 73-81.
3. Pizza, F. X., Flynn, M. G., Duscha, B. D., Holden, J., & Kubitz, E. R. (1995). A carbohydrate loading regimen improves high intensity, short duration exercise performane. International Journal of Sport Nutrition, 5: 110-116.
4. Ahlborg, B., Bergstrom, J., Ekelund, G., & Hultman, E. (1967). Muscle glycogen and muscle electrolytes during prolonged physical exercise. Acta Physiologica Scandinavica, 70(2): 129-142.
5. Coyle, E. F. (1991). Timing and method of increased carbohydrate intake to cope with heavy training, competition and recovery. Journal of Sports Sciences, 9: 29-52.
6. Bussau, V. A., Fairchild, T. J., Rao, A., Steele, P., & Fournier, P. A. (2002). Carbohydrate loading in human muscle: an improved 1 day protocol. European Journal of Applied Physiology, 87(3): 290-295.
7. Tarnopolsky, M. A., Zawada, C., Richmond, L. B., Carter, S., Shearer, J., Graham, T., & Philips, S. M. Gender differences in carbohydrate loading are related to energy intake. Journal of Applied Physiology, 91(1): 225-230.
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