Roadbook
How the fueling planner works
Every number the planner uses, how it is calculated, and the research behind it.
How a plan is built
The ride is split into legs: from the start to the first feed point, from there to the next, and so on to the finish. Each place you stop covers the leg after it, so you arrive at the next stop as you run out.
- Carbs for a leg are your target in grams per hour times the leg's length. With the optional taper switched on, the target falls linearly in the second half of the ride.
- Sweat comes from your sweat profile and the leg's temperature, read from the table below and interpolated between columns. Below the coolest column and above the hottest, it stays at the end value.
- Fluid to drink is a share of that sweat, held to your maximum drinking rate. What you do not replace adds up to the fluid deficit, shown as a percentage of your body weight.
- Sodium is the fluid you drink times a concentration set by how salty your sweat is.
- Caffeine is a dose per kilogram of body weight set by your sensitivity, capped, and rounded to 5 mg. On rides of 3 hours or more it is split into an early dose and a finishing dose; the finishing dose is collected at the last stop before you need it and carried.
- Things to carry: fluid becomes bottles to the nearest half. Carbs from drink mix count for what you drink, and the rest becomes whole gels or bars, with the rounding shown.
The numbers and their sources
A number marked FondoLab default is our judgement, not a study's finding; we say so rather than borrow authority.
| Number | Value | Basis |
|---|---|---|
| Single-sugar limit | 60 g/h | Glucose is absorbed through SGLT1, which saturates around 60 g/h. Above it the plan asks for glucose and fructose together. [1] |
| 2:1 glucose:fructose up to | 90 g/h | About 90 g/h with a 2:1 glucose:fructose mix is the guideline for long events; the gut can be trained to handle it. [1] |
| Above 90 g/h | 1:0.8 glucose:fructose, trained gut | One small lab study in 11 trained male cyclists absorbed and used 120 g/h at 0.8:1 fructose:glucose without more GI trouble. It did not show a performance gain. Treat intakes above 90 g/h as something to build up to in training. [2][1] |
| Carb taper (optional, off by default) | from 50% of the ride down to 80% of the target at the finish | FondoLab default. Many riders find it harder to eat late in a long ride; we found no study that sets this number, which is why it is off unless you switch it on.
FondoLab default |
| Sweat rate by temperature | 0.4–2.2 L/h (table below) | FondoLab default, set inside the 0.5–2 L/h range typical for athletes and rising with temperature, as sweating does. Your own rate can differ a lot: weigh yourself before and after a ride to find it. [3] |
| Share of sweat to drink back | 75% | FondoLab default. The aim is to keep losses under about 2% of body weight without drinking more than you lose, which is the main cause of exercise-associated hyponatremia. [4][5] |
| Default max drinking rate | 1.0 L/h, adjustable | FondoLab default: a comfortable drinking rate for most riders. We have not yet read a source that sets it; it is yours to change.
FondoLab default |
| Fluid deficit limits | under 2% on target, 2–3% watch it, 3% and more too high | Losing more than 2% of body weight to dehydration compromises performance. The 3% line for "too high" is a FondoLab default. [4] |
| Sodium per litre drunk | 500 / 800 / 1100 mg/L (not very salty / average / salty) | FondoLab defaults, inside the 230–1600 mg/L range of whole-body sweat sodium in athletes. Replacing it through what you drink keeps the amount tied to fluid, so it never encourages overdrinking. [3] |
| Caffeine dose | 6.0 / 4.5 / 3.0 mg/kg (low / medium / high sensitivity) | 3–6 mg/kg reliably improves endurance performance; very high doses bring side effects without more benefit. [6] |
| Caffeine caps | 200 mg per dose, 400 mg per ride | EFSA considers single doses up to 200 mg, and up to 400 mg a day, safe for healthy adults, including during intense exercise. Each dose is capped first, so a heavier or less caffeine-sensitive rider can get less in total than their dose by body weight; the plan says when that happens. [7] |
| Caffeine timing | early dose ~45 min before the start; finishing dose 75 min before the finish on rides of 3h or more | Blood levels peak 30–120 min after swallowing and the half-life is 4–6 h. Caffeine taken later in long events may help more than caffeine taken before the start. The exact 45 and 75 minutes are FondoLab defaults. [6] |
Sweat rate by temperature
| 8°C | 15°C | 21°C | 27°C | 33°C | |
|---|---|---|---|---|---|
| Light sweater | 0.4 L/h | 0.5 L/h | 0.7 L/h | 0.9 L/h | 1.2 L/h |
| Average | 0.6 L/h | 0.8 L/h | 1.0 L/h | 1.3 L/h | 1.6 L/h |
| Heavy sweater | 0.8 L/h | 1.1 L/h | 1.4 L/h | 1.8 L/h | 2.2 L/h |
References
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Jeukendrup A (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine 44(Suppl 1):25–33. doi:10.1007/s40279-014-0148-z
Narrative review with practical guidelines · Reviews studies of trained endurance athletes, mostly cyclists, mostly in the lab. The author was at the Gatorade Sports Science Institute. · Read by us: Full text (open access)
Glucose is absorbed through a sodium-dependent transporter, SGLT1, which saturates at an intake of around 60 g/h. On a single sugar, exogenous carbohydrate oxidation tops out at about 1 g/min.
Fructose uses a different transporter. Taking glucose and fructose together, typically in a 2:1 ratio, raised oxidation to about 1.26 g/min in the studies reviewed.
The proposed guidelines scale with duration:
- About 1 h: a mouth rinse or small amounts of carbohydrate can help.
- 2–3 h: up to about 60 g/h, which a single sugar can deliver.
- Longer, ultra-endurance: about 90 g/h, which needs multiple transportable carbohydrates.
- The advice does not depend on body weight or training status.
The gut is trainable: a high-carbohydrate diet for 28 days increased exogenous carbohydrate oxidation, so high intakes should be practised in training.
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Podlogar T, Bokal Š, Cirnski S, Wallis GA (2022). Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h−1 versus 90 g h−1 at different ratios. European Journal of Applied Physiology 122(11):2393–2401. doi:10.1007/s00421-022-05019-w
Randomised crossover trial · 11 highly trained male cyclists (VO2peak about 63 ml/kg/min), 3 h at a moderate intensity in the lab, after an overnight fast. Small sample; no women; not a performance test. · Read by us: Abstract and results (open access)
Riders took 120 g/h of carbohydrate at a 0.8:1 fructose:glucose ratio, or 90 g/h at the usual 1:2 ratio.
- Exogenous carbohydrate oxidation was higher at 120 g/h (about 1.51 g/min in the last hour) than at 90 g/h (about 1.29 g/min).
- Using the body's own carbohydrate stores was not reduced: the extra intake did not spare glycogen.
- Stomach fullness, cramping and nausea did not differ between conditions in these trained riders.
So intakes above 90 g/h with close to equal glucose and fructose can be absorbed and used by trained riders, but this study does not show they ride faster for it.
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Baker LB (2017). Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Medicine 47(Suppl 1):111–128. doi:10.1007/s40279-017-0691-5
Narrative review · Athletes across many sports, in the lab and the field. The author is at the Gatorade Sports Science Institute. · Read by us: Full text, first third (open access)
Sweating rate and sweat sodium vary widely between athletes and within the same athlete from day to day.
- Whole-body sweating rate typically ranges from about 0.5 to about 2.0 L/h. More than 3 L/h happens but is rare, in extreme heat, at high intensity, or in large athletes.
- Sweating rises with ambient temperature and with exercise intensity, through the heat the body has to lose.
- Whole-body sweat sodium is typically about 10–70 mmol/L, roughly 230–1600 mg/L. Local patches read higher (about 10–90 mmol/L).
- The simplest accurate way to measure your own sweating rate is to weigh yourself before and after exercise.
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Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and Science in Sports and Exercise 39(2):377–390. doi:10.1249/mss.0b013e31802ca597
Position stand · Expert synthesis for people exercising in general, not cyclists specifically. · Read by us: Abstract only
The goal of drinking during exercise is to prevent excessive dehydration, defined as losing more than 2% of body weight to a water deficit, and excessive changes in electrolyte balance, both of which compromise performance.
- Start exercise well hydrated.
- Sweat rates vary a lot between people, so drinking plans should be individual; weighing before and after exercise estimates sweat rate.
- Drinks containing electrolytes and carbohydrate can have benefits over water alone in some circumstances.
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Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. (2015). Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clinical Journal of Sport Medicine 25(4):303–320. doi:10.1097/JSM.0000000000000221
Consensus statement (17 experts) · Endurance athletes in general, with much of the evidence from marathons, ultras and triathlons. · Read by us: Press summary only; the full text needs a subscription. Read the statement before relying on more than the two points below.
Exercise-associated hyponatremia (dangerously low blood sodium) is mainly caused by drinking more than the body can lose through sweat and urine, sustained over a long event.
- The safest individual strategy is to drink when thirsty.
- Drinking to replace every gram of sweat, or more, is the risk; this is why a plan should limit losses, not erase them.
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Guest NS, VanDusseldorp TA, Nelson MT, et al. (2021). International society of sports nutrition position stand: caffeine and exercise performance. Journal of the International Society of Sports Nutrition 18:1. doi:10.1186/s12970-020-00383-4
Position stand · Synthesis of studies in trained and untrained people across many sports; aerobic endurance shows the most consistent benefit. · Read by us: Full text, first third (open access)
Caffeine reliably improves endurance performance, with moderate to large benefits, though the size of the effect differs between people.
- Effective dose: 3–6 mg per kg of body weight. The minimum effective dose may be as low as 2 mg/kg.
- Very high doses, around 9 mg/kg, bring many side effects and are not needed for a benefit.
- The most common timing is 60 min before exercise. Blood levels peak 30–120 min after swallowing it; the half-life is 4–6 h.
- Caffeine gum is absorbed through the cheek and acts faster than capsules.
- In long events, caffeine taken later in the race, closer to fatigue, may help more than caffeine taken before the start; low doses taken late compared well with higher doses taken an hour before.
- Responses vary, so riders should try their dosing and timing in training.
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EFSA Panel on Dietetic Products, Nutrition and Allergies (2015). Scientific Opinion on the safety of caffeine. EFSA Journal 13(5):4102. doi:10.2903/j.efsa.2015.4102
Regulatory scientific opinion · Healthy adults in the EU, from all dietary sources. Separate limits apply in pregnancy and for children. · Read by us: Summary (EUFIC); the opinion itself was not reachable. Read it before relying on more than the points below.
For healthy adults:
- Single doses up to 200 mg raise no safety concerns.
- Up to 400 mg over 24 hours is unlikely to cause harm.
- Both levels also hold for healthy adults doing intense physical exercise.