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Science of Carbohydrate Loading for Cycling




What is carbohydrate loading and why should you do it?

Carbohydrate loading is the process of maximizing your muscle and liver glycogen stores by consuming a large quantity of carbohydrate before endurance exercise. Consuming such a large amount of carbohydrate may increase body mass by 0.5kg-1kg when stored, which could be concerning for cyclists. However, the benefits of greater glycogen stores appear to outweigh the negatives of greater body mass, as carbohydrate loading is shown to improve endurance cycling performance(1,2). Your body has a limited capacity to store glycogen and it will be broken down and utilised as fuel during high intensity exercise. To optimize performance, it is important to maximize your glycogen stores, particularly before competition.


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When and how should you carbohydrate load?

Carbohydrate loading should take place the day before an endurance event that lasts longer than 90 minutes(3). One day of carbohydrate loading is shown to be as effective as three days of loading(4). For optimal glycogen storage the day before the event you should aim to consume 8-10 grams per kilogram of body mass of high glycemic index (GI) carbohydrates(5). Ingestion of high GI carbohydrates such as rice, bread, pasta and cereals appears to result in greater glycogen storage than low GI carbohydrates(6) due to being rapidly digested and absorbed. For example, an individual weighing 70 kg should aim to consume 560-700 grams of carbohydrate the day before an event. Ideally this quantity of carbohydrate should be consumed across evenly dispersed periods throughout the day, i.e. every 2-3 hours. Fat content should be kept relatively low in order to aid digestion of carbohydrate. For an example of a carbohydrate loading day, see the table below.  (Low fibre choices are also advised to avoid feeling bloated.)

Time of Day Food (grams of carbohydrate)
Breakfast 100g low fibre breakfast cereal with milk (90g)

1 medium banana (20g)

300ml orange juice (26g)
Morning snack 1 serving of GO Electrolyte (36g)

1 average pot of low fat fruit yoghurt (16g)

50g raisins (35g)

Oats and honey snack bar (27g)
Lunch Ham salad sandwich with butter (4 slices of white bread) (66g)
Afternoon snack 1 serving of GO Electrolyte (36g)

1 GO Energy bar (44g)

1 medium banana (20g)
Dinner Spaghetti Bolognese (250g white pasta, 150g tomato & basil sauce, 85g turkey mince) (97g)

3 slices of garlic bread (32g)
Evening snack 1 white bagel with jam (55g)

40g porridge oats with 1 tablespoon of honey (20g)

Total calories: 3570 kcal
Carbohydrate: 620g
Protein: 120g
Fat: 70g


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References

  1. Rauch, L. H. G., Rodger, I., Wilson, G. R., Belonje, J. D., Dennis, S. C., Noakes, T. D., & Hawley, J. A. (1995). The effects of carbohydrate loading on muscle glycogen content and cycling performance. International Journal of Sport Nutrition, 5(1), 25-36
  2. Bergström, J., Hermansen, L., Hultman, E., & Salting, B. (1967). Diet, muscle glycogen and physical performance. Acta Physiologica, 71(2-3), 140-150
  3. Hawley, J. A., Schabort, E. J., Noakes, T. D., & Dennis, S. C. (1997). Carbohydrate-loading and exercise performance: an update. Sports Medicine, 24(2), 73-81
  4. 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
  5. Burke, L. M., Hawley, J. A., Wong, S. H. S., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of Sport Sciences, 29(sup1), S17-S27
  6. Wee, S. L., Williams, C., Tsintzas, K., & Boobis, L. (2005). Ingestion of a high-glycemic index meal increases muscle glycogen storage at rest but augments its utilization during subsequent exercise. Journal of Applied Physiology, 99(2), 707-714
Ted Munson (Performance Nutritionist)
Written By

Ted Munson (Performance Nutritionist)

Ted is a Performance Nutritionist here at Science in Sport.