You may have heard stories of people preceding a carbohydrate load with a "carb-depletion phase", in order to ‘prime their muscles’ to take up extra fuel.
But are they doing the right thing?
Is depleting your glycogen stores the right move?
There is strong evidence to suggest that you can reap the benefits of a carb load (higher carb intake than normal) without having to decrease your carb intake beforehand.
The concept of carb-depletion emerged in the 1960s, as original studies instituted a protocol of three days of low carb intake and training, followed by three days of high carbs and a taper.
The results showed a higher than normal amount of glycogen stored in the muscles, which corresponded to a longer time to complete exhaustion during exercise.
But, it’s important to note that these studies used ‘physically active’ individuals rather than specifically trained athletes. Since then, the consensus has shifted to the idea that rest, reduced training volume and the consumption of a high-carb diet are the key things needed to stimulate supercompensation in well-trained athletes.
Is ‘glycogen-depletion’ real?
Yes, it's possible to meaningfully deplete your muscle glycogen stores - and this can be achieved in as little as 90-120 minutes of intense exercise - and augmented through following a low carbohydrate diet.
But, by delaying the depletion of the stores during exercise, you can delay the onset of fatigue.
So yes, the act of glycogen depletion is real, but we don’t necessarily need it to encourage extra glycogen storage.
Is ‘glycogen supercompensation’ real?
Yes, it's clear that there's an increase in muscle glycogen content following a high dietary carb intake. The ability to 'top your levels off' has also been shown to be greater in fitter individuals.
The subsequent positive effect on performance is seen most notably in endurance exercise lasting more than 90 minutes.
Even if you only have around a day to carb load, the science shows you can still achieve an impactful level of glycogen supercompensation.
That’s assuming you’re able to rest up and get in a significant amount of carb relative to your bodyweight. The study above had athletes put their feet up for 24 hours whilst eating 10g of carb per kilogram of bodyweight per day.
So, if you weigh 60kg (132lbs), that means 600g of carb in 24 hours. For context, one bagel is typically around ~50g of carb. Unless you want to work your way through a dozen bagels, you’ll need to use some more energy dense and perhaps liquid sources of carbs, with many athletes that we work with using Carb Only Drink Mix for this very purpose.
Key takeaways
- Carb-loading before a race can delay the onset of fatigue, particularly in events lasting more than 90 minutes
- You don’t need to deplete your carb stores before loading them up
- Make sure you eat enough carbs, aiming for 8-12g/kg (3.6g-5.4g/lb), and that you rest up
- If you only have one day to carb load, go for the higher end of 10-12g/kg (4.5-5.4g/lb)
- Consider using liquid and energy-dense sources of carbs to avoid feeling overfull
- Storing carbohydrates pulls water into your cells (carbo-HYDRATE), so don’t be surprised if you see a 2-3% increase in your scale weight. This is a good sign
