Field notes · 6 September 2026 · Alastair McDowell
How much carbohydrate an hour, and why 2:1
Sixty, ninety or a hundred and twenty grams an hour. Where those numbers come from, how to find yours, and why POWTREK GEL is built at a 2:1 maltodextrin to fructose ratio.
Every fuelling conversation eventually arrives at a number of grams an hour. This note is about where the common numbers come from and how they translate into a flask of POWTREK GEL, so the dose on the bag is a decision rather than a guess.
The two doors
Carbohydrate gets from your gut into your blood through two main transporters. One handles glucose, which is what maltodextrin becomes once it is broken down. The other handles fructose. Each has a ceiling.
The glucose door tops out at roughly 60 grams an hour. Push more glucose at it and the extra sits in the gut. The fructose door adds capacity on top, which is why every serious endurance mix for the last fifteen years has used both sugars rather than one.
That is the whole reason a ratio exists. It is not flavour and it is not marketing. It is two doors with two different capacities.
The common targets
Around 60 grams an hour. The long-standing recommendation for efforts over about two hours, and a comfortable place for most people on most long days. At this rate the glucose door is doing nearly all the work, so the ratio matters less.
Around 90 grams an hour. The target for long races once the gut is trained to it. Now the glucose door is full and about a third of the load has to go through the fructose door. A 2:1 maltodextrin to fructose mix is built for exactly this: 60 through one door, 30 through the other.
100 to 120 grams an hour and beyond. Where committed racers and a lot of cyclists sit. Every additional gram above 90 has to travel as fructose, because the glucose door is closed. The ratio has to move towards parity, which is why the high-rate mixes on the market sit around 1:0.8.
Which POWTREK bag
POWTREK GEL is 2:1, built for the 60 to 90 gram an hour range where most people, most of the time, actually fuel.
Turning the number into a flask
A standard flask of GEL is 200 grams of powder made up with 150 mL of hot water, which fills a 250 mL soft flask and carries about 180 grams of carbohydrate. So:
| Target rate | One flask lasts | Flasks for a 6-hour day |
|---|---|---|
| 60 g an hour | about 3 h | 2 |
| 75 g an hour | about 2 h 25 min | 2 and a half |
| 90 g an hour | about 2 h | 3 |
| 120 g an hour | about 1 h 30 min | 4 |
Drink plain water alongside. The flask is the carbohydrate; your bottles are the hydration. Keeping the two separate is what lets you adjust one without the other on a hot day.
Finding your own number
Start where you are comfortable, probably 60, and add 10 grams an hour every couple of long sessions. The gut adapts like anything else. Stop going up when the extra grams stop helping or start to sit heavily, and hold there. Most people land between 70 and 90. Some land higher. The bag does not care; you set the dose.
Nothing here is medical advice. If you have a diagnosed condition that touches on how you absorb carbohydrate, ask someone qualified before you change what you fuel with.