Zo werkt de voedingsplanner

Zo komt een plan tot stand

De rit wordt opgedeeld in trajecten: van de start naar de eerste bevoorrading, van daar naar de volgende, en zo verder tot de finish. Elke plek waar je stopt dekt het traject erna, zodat je bij de volgende stop aankomt als je bijna door je voorraad heen bent.

• Koolhydraten voor een traject zijn je doel in gram per uur maal de lengte van het traject. Als je de optionele afbouw aanzet, daalt het doel in de tweede helft van de rit geleidelijk.
• Zweet volgt uit je zweetprofiel en de temperatuur op het traject, afgelezen uit de tabel hieronder en geïnterpoleerd tussen de kolommen. Onder de koelste kolom en boven de warmste blijft het op de waarde aan dat uiteinde.
• Vocht om te drinken is een deel van dat zweet, begrensd op je maximale drinksnelheid. Wat je niet aanvult, telt op tot het vochttekort, getoond als percentage van je lichaamsgewicht.
• Natrium is het vocht dat je drinkt maal een concentratie die afhangt van hoe zout je zweet is.
• Cafeïne is een dosis per kilogram lichaamsgewicht die afhangt van je gevoeligheid, begrensd en afgerond op 5 mg. Bij ritten van 3 uur of langer wordt die verdeeld over een vroege dosis en een slotdosis; de slotdosis pak je bij de laatste stop voordat je hem nodig hebt en neem je mee.
• Wat je meeneemt: vocht wordt afgerond op halve bidons. Koolhydraten uit sportdrank tellen voor wat je drinkt, en de rest wordt hele gels of repen, met de afronding erbij.

De getallen en hun bronnen

Een getal met FondoLab-standaard is ons eigen oordeel, geen uitkomst van een studie; dat zeggen we liever dan dat we gezag lenen.

Zweetverlies per temperatuur

Bronnen

De bronnen zijn Engelstalig, en onze aantekeningen erbij ook.

1. 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. · Door ons gelezen: 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.

2. 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. · Door ons gelezen: 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.

3. 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. · Door ons gelezen: 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.

4. 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. · Door ons gelezen: 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.

5. 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. · Door ons gelezen: 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.

6. 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. · Door ons gelezen: 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.

7. 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. · Door ons gelezen: 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.