Glycogen replenishment after exercise: science and timing

Glycogen is the fuel the body stores in some of its different parts to allow muscles to function during sustained exercise sessions. It is stored in many parts of the body – but, for the purpose of this discussion, we look only at storage inside the muscles themselves and the liver, which together store a large reserve (approximately 450-550 grams for an average-sized adult) that is readily available during exercise, but which can be fully depleted during long and sustained exercise sessions.

Research on glycogen muscle and liver replenishment indicates that, for both, the use a combination of roughly 3:1 carbs to protein for replenishment maximizes the speed of glycogen replenishment, as compared to pure carbs and to pure proteins (when tested for plasma insulin response).

The 60-120 minutes immediately following exercise are particularly suited to glycogen replenishment, with accelerated storage during that period.

Full replenishment for glycogen can be reached, with favorable nutrition (high carb diet and frequent ingestions), in 20 to 24 hours. In the first 5 hours, glycogen replenishment may reach up to 5% of total storage per hour, slowing down later.

As a note, a high-carb diet for three days prior to a long exercise session may allow for higher glycogen storage during the sports event.

Partial sources

End of wiki ---------- comments start here

This quote from the Sport Journal reference article is missing an important detail.
“The body stores approximately 450-550 grams of glycogen within the muscle and liver for use during exercise.”

That range depends on a person’s size. It’s about 10 grams per kilogram of muscle tissue, plus whatever is stored in the liver, which depends on metabolic rate, diet, and conditioning.

On the ideal ratio of carbs to protein, this number is much debated. But the ratio of carbs to protein depends on how many carbs you are getting. If you are not getting as many carbs, a little higher ratio of protein is helpful. If you are getting a good bit of carbs, then the protein is not as important for glycogen replacement. BUT the protein is still important for muscle repair.

The addition of certain amino acids and/or proteins to a carbohydrate supplement can increase muscle glycogen synthesis rates, most probably because of an enhanced insulin response. However, when carbohydrate intake is high (> or =1.2 g/kg/h) and provided at regular intervals, a further increase in insulin concentrations by additional supplementation of protein and/or amino acids does not further increase the rate of muscle glycogen synthesis. Thus, when carbohydrate intake is insufficient (<1.2 g/kg/h), the addition of certain amino acids and/or proteins may be beneficial for muscle glycogen synthesis.

Sam posted a question about this yesterday. I gave him a formula that came up with 102 grams in an example. Based on the link above, it would give him 97 grams. So, there you go @Sam! That’s pretty close.

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