Beyond “60⁠–⁠90 g/h”: where your number comes from

The range isn't wrong: it is the recommendation for rides over 2.5 h. The problem is applying it to everything. On a ride under 75 min you don't need to eat (at most, rinse your mouth with a sports drink); between 75 min and 2.5 h the guideline is 30 to 60 g/h; and within each range, an easy ride doesn't call for the same as a hard one.

Two riders on the same route can burn very different amounts of carbohydrate: it depends on the watts they push and on how much of that energy comes from glycogen. But how much to eat on the bike is set mainly by the ride's duration and by what the gut can absorb, not by body weight: the guidelines do not scale g/h per kilo (Jeukendrup, 2014).

That's why RATIO keeps two separate accounts. What you burn: from watts to kilojoules, and from kilojoules to the grams of carbohydrate you use. And what you should eat: from the duration and intensity to the grams your gut can absorb. Both are explained below.

It starts by converting the metric your power meter already measures — watts — into a real unit of mechanical work: the kilojoule. This is a physical conversion, not an estimate:

That work is not the metabolic cost: the body turns only part of the energy into movement. That part, gross efficiency (GE), is around 18⁠–⁠23% depending on the rider and the intensity (Moseley et al., 2004). RATIO uses 20% and gives the cost as a range from 18 to 22%.

That's why RATIO starts from watts, not from “how hard did that feel?”: perceived exertion (RPE) is only used when a ride has no power, heart rate or data to estimate it.

Ref: Moseley, L., Achten, J., Martin, J.C. & Jeukendrup, A.E. (2004). No differences in cycling efficiency between world-class and recreational cyclists. International Journal of Sports Medicine, 25(5), 374⁠–⁠379; Moseley, L. & Jeukendrup, A.E. (2001). The reliability of cycling efficiency. Medicine & Science in Sports & Exercise, 33(4), 621⁠–⁠627.

Not all the energy comes from carbohydrate: at low intensity a large part comes from fat, and the carbohydrate share rises with intensity. In trained, fasted cyclists it was 46% at 40% of maximal power and 76% at 75% (van Loon et al., 2001). Eating on the bike raises that share somewhat, and people differ a lot.

RATIO works out that cost in 30-second stretches: with real power once the ride exists, and with a pedalling model for a plan. That cost feeds the balance and the recovery, and always comes with a range (±10 points in the carbohydrate share). What it recommends eating on the bike comes from the duration and your gut, not from the cost: nobody absorbs on the bike everything they burn.

Ref: van Loon, L.J.C. et al. (2001). The effects of increasing exercise intensity on muscle fuel utilisation in humans. The Journal of Physiology, 536(1), 295⁠–⁠304.

Knowing how many grams of carbohydrate to take solves nothing if the gut can't absorb them at that rate. The intestinal epithelium transports glucose and maltodextrin exclusively through the sodium-dependent transporter SGLT-1, which saturates at around 60 g/h. Pushing past that figure with maltodextrin alone doesn't speed up absorption — it just accumulates undigested solute in the intestinal lumen, causing the gastrointestinal distress any cyclist recognizes past the two-hour mark.

The fix, documented by Jeukendrup (2010, 2014) and Jentjens & Jeukendrup (2005), is recruiting a second, sodium-independent transport pathway — GLUT-5, specific to fructose — that operates in parallel with SGLT-1 without competing for the same channel. Combining both sugars, total absorption can reach about 90 g/h; above that, up to 120 g/h, there are studies in athletes with a very trained gut, and RATIO treats it as experimental.

RATIO doesn't change the recipe with every ride: there are two fixed mixes, made at home from the same two bags. Up to 60 g/h the 2:1 fits —at that rate the ratio matters little and it has less fructose—; above it, the 1:0.8, which is absorbed better as the rate goes up (Podlogar, Wallis et al., 2022). The planner marks the one that fits the plan, without picking it for you.

So where does the hourly figure in that mix come from? Not from the cost. It comes from the range for the ride's duration, placed within it by the intensity (from NP/FTP 0.55, the minimum, to 0.85, the maximum), and capped by your carb ceiling, from 30 to 90 g/h: it starts from your answer in Gut tolerance and then the rides you log in “Your ride” adjust it.

Ref: Jeukendrup, A.E. (2010). Carbohydrate and exercise performance: the role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition and Metabolic Care, 13(4), 452⁠–⁠457; Jeukendrup, A.E. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(S1), 25⁠–⁠33; Jentjens, R.L.P.G. & Jeukendrup, A.E. (2005). High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise. British Journal of Nutrition, 93(4), 485⁠–⁠492.

Two riders with the same FTP can burn different shares of fat and carbohydrate at the same intensity. People differ a lot, and a profile label rarely explains it (Jeukendrup & Wallis, 2005). That is why the cost is shown as a range.

The second limitation of average power is subtler: it can't tell a steady flat ride apart from a VO2 max interval session broken up by long recoveries. Both can share the same average power — but the second spends a meaningful fraction of its time well above that average, exactly where the share of energy coming from carbohydrate spikes. Averaging hides precisely the data point that determines real glycogen expenditure.

When there is real power, from a finished ride or a structured workout, RATIO works stretch by stretch. In a plan, with no power yet, it uses a pedalling model for the chosen zone: its normalized power (NP), with part of the descents spent coasting.

Ref: Palmer, G.S., Borghouts, L.B., Noakes, T.D. & Hawley, J.A. (1999). Metabolic and performance responses to constant-load vs. variable-intensity exercise in trained cyclists. Journal of Applied Physiology, 87(3), 1186⁠–⁠1196.

“60⁠–⁠90 g/h” is a good starting point for a long ride. What it lacks is context: how long your ride is, how hard it is and how much your gut absorbs. And it shouldn't be confused with what you burn, which is a different figure and almost always a larger one.

That's the work RATIO's engine does every time it calculates a plan: it turns watts into the carbohydrate cost, with its range; it picks how much to eat from the duration, the intensity and your gut; and it turns that figure into a bottle mix that respects the absorption limits — without you ever having to memorize a single formula.

You can review every formula, threshold, and full bibliographic citation in Scientific foundation.