Thursday, April 19, 2007

Adding fuel to the fire. Carbohydrate loading for the athlete

In endurance exercise of greater than a 90 minute duration (marathon running), muscle-glycogen stores become depleted. This depletion limits the performance. Carb-loading, also called glycogen supercompensation, is a technique used to increase muscle glycogen prior an endurance event. This practice can nearly double muscle-glycogen stores, increasing endurance potential.

Historically, the week-long program includes four days of glycogen depletion (through a low-carb diet and exhaustive exercise), followed by three days of rest and a high-carb diet. This method had many drawbacks, including periods of hypoglycemia, irritability, increased susceptibility to injury and difficulty in compliance. In 1981, one study proposed a revised method that accomplishes the same goal with greater ease of compliance and fewer side effects.

  • 6 days out: 70-75% intensity for 90 minutes, carbs = 4 g/kg of body weight
  • 4-5 days out: 70-75% intensity for 40 minutes, carbs = 4 g/kg of body weight
  • 2-3 days out: 70-75% intensity for 20 minutes, carbs = 10 g/kg of body weight
  • 1 day out: Rest, carbs = 10 g/kg of body weight

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