What’s the science in carb loading for a 20 min max effort?

Have a hill climb race tomorrow that starts with a 30 min warm up followed by a 20 min max effort. Never considered whether I should load up the day beforehand.

Interested to hear if it’s worth doing?


I have no science other than my experience. For me loading is a week long process. I try to stay pretty carb loaded up all the time unless I’m trying to drop a few pounds. That being said, the only benefit I would get from loading for a 20 min effort would be better recovery.

I think I read once that a lot of it (Carb Loading) is phycological but thats like 90% of stuff in cycling and if it work for you, it works :slight_smile:

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Tough call. If it was a crit, I’d say the extra lb or three are well worth it for the available energy, but for a hill climb, you need to consider the trade off.

If you have time, try a carb load and a similar climb.

FWIW, I’ve never regretted carbing up for a race.

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defo on the caffeine. doing 150mg

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You will not run out of glucose in 20 min. Don’t worry about it.


300W for 20min would burn about 80-100g of carbs so it won’t be hard to get enough in you to fuel it. But when I am full up I feel amazing and my legs look killer. So that’s not worthless :grin:

If you are on the flat weight wont matter and I’d up my carb intake for a few days before and make sure I was topped off on the morning and day of the event.

If this is a steep as all hell hill climb you might consider that every gram of glycogen stored in your muscles is accompanied by 3g of water. So that storage comes with a weight penalty (you can be up as much as 4lbs with a proper carb load). The extra 1kg of weight could be worth a few watts (1w at 1w/kg and 6w at 6w/kg).

Science says that carbohydrate loading is generally only beneficial in events 90 min or longer.


…on average, in frog muscle.

(Point being that the ratio isn’t fixed.)

True ( PMID: 1615908) said it can be as many as 4 parts water. 3 is typical for papers to reference so I figured it was safe. 4g would make it even worse as far as the loss of excess loading in a very steep hillclimb though