The role of carbohydrates in endurance sports - truefuels

The role of carbohydrates in endurance sports

Why endurance sport relies on carbohydrate

Carbohydrates are the body’s preferred fuel during moderate to high-intensity exercise. Once digested, starches and sugars appear in the bloodstream as glucose; any surplus is stored as glycogen in the liver and muscle for rapid release when exercise intensity rises (Jeukendrup & Killer, 2010). At high exercise intensities, glycogen stores can be depleted within a couple of hours; if blood glucose levels fall, power output drops quickly. Multiple studies confirm that maintaining carbohydrate availability during exercise improves performance and delays fatigue (Sherman et al., 1981). Historically, the practical ceiling for intake was approximately 60 g/h because it saturates the glucose transporter SGLT-1; excess glucose left in the intestine can cause gastrointestinal discomfort (Jeukendrup & Killer, 2010).

Opening a second carbohydrate lane

The intestine also contains a fructose-specific transporter, GLUT5. Providing glucose and fructose together engages both transporters, raising total absorption to about 90 g · h⁻¹ and, for well-trained athletes, even 120 g · h⁻¹ (Jentjens & Jeukendrup, 2005). Laboratory trials using glucose-to-fructose ratios, such as 2:1 or 1:0.8, record up to 40% higher exogenous oxidation rates and faster cycling time-trials than glucose alone (Currell & Jeukendrup, 2008; Rowlands, Hopkins, & Irwin, 2016). Ingredient quality matters: unnecessary flavours, fillers, or preservatives can slow gastric emptying and increasing GI risk, so shorter ingredient lists usually mean more predictable absorption.

Estimating your own fueling needs

Carbohydrate requirements depend on session length, intensity, environmental conditions, and individual gut tolerance. A short, easy ride may need nothing more than a banana (β‰ˆ 25-30 g of carbohydrate). For longer or harder efforts, the guide below offers a starting point:

Session type Typical intake (g · h⁻¹)
< 1 h, low intensity up to 30
1–2 h, steady endurance ~60 (mixed carbs)
> 2 h, high exercise intensities 90–120 (mixed carbs)

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In the two days before a key event, aim for 10-12 g kg⁻¹ day⁻¹ of carbohydrate to maximise muscle glycogen (Sherman et al., 1981).

The Truefuels approach:

β€’ 1:1 maltodextrin: fructose blend engages both transporters and provides a steady supply without large blood-glucose swings.

β€’ Two salt levels let you match electrolyte intake to sweat rate while stacking servings to hit your carbohydrate target.

β€’ Minimalist formulation: only essential ingredients reduces the risk of GI issues.

For a personalised plan, the calculator at https://truefuels.com/pages/fuel-guide converts event duration, temperature, and sweat profile into grams per hour and sachets per bottle.

Key points to remember

  1. Carbohydrate is essential when exercise lasts longer than about an hour.
  2. Combining glucose and fructose safely raises intake to 90-120 g · h⁻¹ for well-trained athletes.
  3. Practice your fueling strategy in training so your gut adapts along with your muscles.
  4. Simple formulations minimise gastrointestinal risk.

References:Β 

[1] Currell, K., & Jeukendrup, A. E. (2008). Superior endurance performance with ingestion of multiple transportable carbohydrates. Medicine & Science in Sports & Exercise, 40(2), 275–281. https://doi.org/10.1249/MSS.0b013e31815c54ae

[2] Jeukendrup, A. E., & Killer, S. C. (2010). The myths surrounding pre-exercise carbohydrate feeding.Β International Journal of Sport Nutrition and Exercise Metabolism, 20(1), 12–30. https://doi.org/10.1123/ijsnem.20.1.12

[3] Jentjens, R., & Jeukendrup, A. E. (2005). High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling.Β Journal of Applied Physiology, 98(2), 678–686. https://doi.org/10.1152/japplphysiol.00862.2004

[4] Rowlands, D. S., Hopkins, W. G., & Irwin, C. (2016). Glucose–fructose co-ingestion: Exogenous carbohydrate oxidation and performance of prolonged cycling.Β International Journal of Sport Nutrition and Exercise Metabolism, 26(5), 460–468. https://doi.org/10.1123/ijsnem.2016-0064

[5] Sherman, W. M., Brodowicz, G. R., Wright, D. W., Allen, W. K., Simonsen, J. J., & Hartmann, B. R. (1981). Effects of exercise and carbohydrate feeding on muscle glycogen utilisation in humans.Β Journal of Applied Physiology, 51(3), 940–944. https://doi.org/10.1152/jappl.1981.51.3.940

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