Pre-Workout Nutrition, Part II: Carbohydrate Loading

huge plate of pasta
Stephanie Fernandes

Stephanie Fernandes

MS, RD/LDN, METS I, ISAK I

Beginning a key training session or competition with sufficient carbohydrate stores is important for preventing fatigue and impairments in cognitive function.  

Many athletes have heard the term ‘carbohydrate loading, but yet gets often misunderstood or misused.

Carbohydrate loading is the practice of achieving super-compensation of muscle glycogen (the storage form of carbohydrate in the muscle and liver and primary energy source for working muscles), which reaches above maximal levels of glycogen in the muscle.

The OG protocols from the late 1960s1 require some fairly extreme measures and don’t seem practical in real-world scenarios.

More recent research was able to demonstrate effective super-compensation with consuming higher amounts of carbohydrate paired with rest in 24-36 hours before the competitive event.3

Carbohydrate loading appears to benefit performance during endurance events lasting 90 minutes or more4 by delaying fatigue and improving performance by 2-3%.5

Athletes who would benefit from this carbohydrate loading would include:

  • Distance runners – marathons, Ironman, ultra-endurance races,
  • Cross-country skiers,
  • Road cyclists, and
  • Other endurance events with durations longer than 90 minutes.

To optimize muscle glycogen stores, athletes participating in these types of events will need to:  

  • Include 24-36 hours of rest or tapered exercise paired with 
  • 7-12 g of carbohydrate/kg of body weight.

Eating upwards to 10g of carbohydrate/kg of body weight per day is a sizable amount of carbohydrates. For a 150 pound (68 kg) athlete, you are looking at 680 g of carbohydrate (approximately 2,700-3,270 kcal). What does 680 g of carbohydrates look like? That would be 15 cups of rice or 25 medium bananas!

Again, this is necessary only when carbohydrate loading is desired or when your glycogen levels are significantly deficient.

Soccer player kicking

In sports with repeated bouts of high intensity exercise, that typically last around 60-90 minutes of playing time, the energy demands aren’t as clear cut.

During a soccer match, muscle glycogen levels can be depleted up to 67% by half-time and >90% at the conclusion of the match.6

We can theorize that maximizing glycogen stores would be beneficial as the combination of prolonged duration and intermittent high-intensity exercise require a higher rate of glycogen use, and depletion of these stores is a limiting factor for performance – fatigue and impaired cognitive function.

Sports that have shown to benefit from such strategies include soccer and ice hockey.7,8,9

Carbohydrate loading is not universal to all sports and athletes. Take Michael Scott. There are few other mistakes in his “pre-race” nutrition. Still, carbohydrate loading for that 5K charity fun run is 1) not going to provide any benefit to his performance and 2) he crushed that Fettuccine Alfredo <60 minutes before the race so timing is way off and I probably why he had some severe GI issues during the race. 

Continuous, prolong exercise <90 minutes and intermittent, high-intensity training, that last <60-90 minutes, do not benefit from super-compensated muscle glycogen stores, and normal stores of carbohydrate are adequate in meeting the fuel demands.2,5

Though carbohydrate loading is not necessary, adjustments in training and nutrition, such as:

  • Inclusion of rest or light training day,
  • Avoidance of training sessions that cause significant muscle damage, and
  • Following high carbohydrate eating patterns in the day prior can optimize muscle glycogen stores.

We could speculate that sports such as basketball and tennis, and positions such as starting pitchers in baseball and softball would benefit from optimizing muscle glycogen stores before key training sessions and competition.

The use of carbohydrate loading in team sports is not universal and is often specific to the individual athlete based on play position or style.

Logistically as well, many team sports play games or matches daily or multiple times per week, and conventional carbohydrate loading protocols would not be practical given the limited time between competitive events.  

We recommend for these athletes to increase carbohydrate intake the day before their game or match and maintain a carbohydrate intake that matches or meets the fuel required if they are playing multiple games or matches consecutively with very few days of rest.

References

  1. Bergstrom, J. & Hultman, E. (1967) A study of the glycogen metabolism during exercise in man. Scandinavian Journal of Clinical and Laboratory Investigation, 19(3), 218-228.
  2. Sherman, W. M., Costill, D. L., Fink, W. J., & Miller, J. M. (1981). Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilisation during performance. International Journal of Sports Medicine, 2, 114–118.
  3. Bussau, V. A., Fairchild, T. J., Rao, A., Steele, P. D., & Fournier, P. A. (2002). Carbohydrate loading in human muscle: An improved 1 day protocol. European Journal of Applied Physiology, 87, 290–295.
  1. Thomas, D.T., Erdman, K.A., Burke, L.M. (2016). American College of Sports Medicine Joint Position Statement: Nutrition and athletic performance. Medicine and Science, 48, 543-568.
  1. Hawley JA, Schabort EJ, Noakes TD, Dennis SC. Carbohydrate loading and exercise performance. An update. Sports Medicine, 1997;24(2):73–81.
  1. Saltin, B. (1973). Metabolic fundamentals in exercise. Medicine & Science in Sport and Exercise, 5, 137-146.
  2. Bangsbo, J., Norregaard, L., & Thorsoe, F. (1992). The effect of carbohydrate diet on intermittent exercise performance. International Journal of Sports Medicine, Feb, 13(2), 152-7.
  1. Balsom, P.D., Wood, K., Olsson, P., & Ekblom, B. (1999). Carbohydrate intake and multiple sprint sports: with special reference to football (soccer). International Journal of Sports Medicine, Jan, 20(1), 48-52.
  1. Burke, L., & Deakin, V. (2015). Clinical Sports Nutrition. (4th ed.). McGraw-Hill Education (Australia) Pty Ltd.
  1. Akermark, C., Jacorbs, I., Rasmusson, M., & Karlsson, J. (1996). Diet and muscle glycogen concentration in relation to physical performance in swedish elite ice hockey players. International Journal of Sport Nutrition and Exercise Metabolism, 6(3), 272-284.

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