Glycogen is the storage form of glucose. Carbs, either directly from glucose, or when other forms, such as fructose and galactose are converted to glucose, will it be converted to and stored as glycogen in the liver and muscles when those stores ain’t full yet.
The liver stores an average of 100g of glycogen and this can be boosted up to 200g and even higher. Muscle glycogen content is around 300g and can go up to 500g when you have a decent amount of muscle and even over 700g for a very muscular guy.
Topped up glycogen stores enhances exercise performance, and having glucose around is very important for general health as well, such as thyroid hormone conversion, detoxification, keeping cortisol at bay, etc.
Caffeine can increase muscle glycogen even when the glycogen stores are already topped up – supercompensation. That’s right. In this study, they depleted athletes’ glycogen stores and then fed them lots of glucose to promote the supercompensation effect. So before even using the caffeine, their muscles had more glycogen than what it would normally store. Then, when their stores where supercompensated, the researchers gave them caffeine at a dose of 6mg/kg 90min pre-workout with additional glucose. The caffeine group saw a 140% increase in muscle glycogen over the group that didn’t receive caffeine (R).
It is well known that caffeine does have an exercise performance-boosting effect via increasing beta-endorphins, catecholamines and having a glycogen sparing effect. To add to the long list of benefits of coffee and caffeine is that it increases muscle glycogen.
Something to keep in mind:
We now know that caffeine pre-workout will increase muscle glycogen, but what about post-workout?
Caffeine does speed up glycogen resynthesis after a workout only when carbs are provided at a pace below 1.2g/kg/hour. For instance, if 80g of carbs (1g/kg/BW) are provided post-workout to an 80kg athlete per hour, caffeine will speed up glycogen resynthesis (about 66% faster) (R). This is because caffeine stimulates glucose uptake into muscle in an insulin-independent manner, by increasing GLUT4, a glucose transporter (R).
But if more than 96g carbs (>1.2g/kg/BW) are provided post workout per hour caffeine won’t speed up glycogen resynthesis.
General rule: caffeine will speed up glycogen resynthesis post workout if less than 1.2g/kg of carbs per hour are provided, but not if more than 1.2g/kg/hour are provided.
Interestingly, circulating insulin levels are not the rate-limiting factor for muscle glycogen synthesis when post-workout carb intake is over 1.2g/kg/hour. So using things like caffeine, ketone esters or insulinogenic amino acids with carbs post-workout will not further speed up glycogen resynthesis (R). But they will speed up glycogen resynthesis when less than 1.2g/kg/hour of carbs are ingested.
To get back on point, caffeine might not speed up glycogen resythnesis post-workout when enough carbs are provided, but it will increase the total amount of glycogen in the muscle when it is already topped up. Caffeine will promote the supercompensation effect.
How and when is the most important time to take your caffeine?
Take 200-400mg caffeine 90-30 min pre-workout with a bunch of carbohydrates. A fructose/glucose mix would be optimal. More on that in the future.
P.S. Taking your caffeine with carbs will also help to prevent a stress reaction that you might normally get from caffeine.
As a bonus, you can take your caffeine with taurine, as the taurine will increase the amount of glycogen your liver can store as well. Double win!
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