Endurance Athletes: Ready, Set, Carb-load!

by Brooke on September 25, 2012

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Carbohydrates are used at a high rate at the beginning of exercise, since our fat stores can’t be broken down as quickly to make energy (ATP).   Consumption of carbohydrates prior to exercise increases an athlete’s energy stores in the body and helps delay the onset of fatigue.  Sugar (glucose) is stored mainly in the liver and muscles as glycogen.  Glycogen stores get depleted during exercise.  Carbohydrate loading is often done by endurance athletes to prepare for a competition/race to help increase their glycogen stores.  Carbohydrate loading is most effective for athletes exercising longer than 90 minutes; examples of such athletes include marathon runners, swimmers, cyclists, and triathletes.

Carbohydrate loading helps enhance performance because:

  1. Higher than average muscle glycogen stores will postpone fatigue, thus increasing the time to exhaustion.
  2. If an athlete doesn’t feel fatigue as quick they will be able to maintain their pace for a longer period of time.
  3. It allows your body to use less fat as energy.  Fat takes longer to breakdown, so if your body has easy access to glycogen stores you will be able to perform at a higher intensity.
  4. It spares protein stores, so your body doesn’t need to breakdown your muscles.
  5. It can help delay or prevent that “hit the wall” feeling when your body is actually running out glycogen and needs to begin breaking down fat and muscle stores.

There have been a few different carb-loading procedures used in the past.  One used a three day glycogen-depleting exercise regimen and another used a low carbohydrate diet regimen lasting six days.  Both of these methods were very taxing on athletes and interfered with their training taper.  Sherman et al developed the method we currently use today.  He devised a six day regimen that allows for a lower carbohydrate intake the first three days and a higher carbohydrate intake during training taper.

His revised carbohydrate loading guidelines include training at 70% of VO2max, but to keep things simple I just made the chart without it.   This table was adapted from Sports Nutrition: A Practice Manual for Professionals.



Carbohydrates   g/kg


90 min



40 min



40 min



20 min



20 min








Here is an example on how to use this chart.  Shelly weighs 130 pounds and is in day four of the carb loading phase.  She would need to train for 20 min and consume 591 grams of carbohydrates for that day.

The math:  130 pounds \ 2.2 = 59.09 kilograms (kg)  >  10 grams of carbohydrates  x  59.1  =   591 grams of carbohydrates recommended for that day.

If you need more help following a carb loading diet please contact your Registered Dietitian!



Benardot, Dan. Advanced Sports Nutrition. Champaign: Human Kinetics, 2000.

Dunford, Marie. Sports Nutrition: A Practice Manual for Professionals, 4th Edition. American Dietetic Association, 2006.

Position of the American Dietetic Association,. Dietitians of Canada, and the American College of. Sports Medicine: Nutrition and Athletic Performance. J Am Diet Assoc. 2000 Dec;100(12):1543-56.

Sherman, W. M., Doyle, J. A., Lamb, D. R., & Strauss, R. H. (1993). Dietary carbohydrate, muscle glycogen, and exercise performance during 7 d of training. The American Journal of Clinical Nutrition, 57, 27-31.


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Emily September 25, 2012 at 2:43 pm

I always love these posts. It makes me want to start running again! Also, that pasta looks yummy!


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