Exercise duration & carbohydrates: why your energy supply during training is crucial
Carbohydrates are one of the most important sources of energy in endurance sports. The right carbohydrate intake plays a key role in your performance, especially during intense exercise lasting longer than an hour.
Why carbohydrates are so important in endurance sports
Your body has limited carbohydrate stores - in the form of glycogen in the muscles and liver. These stores are sufficient for around 60 to 90 minutes of moderate to high exertion, depending on your training status and diet. After that, the energy supply becomes increasingly critical, which can manifest itself in a drop in performance, poor concentration and a strong feeling of exhaustion.
To prevent this from happening, a targeted supply of carbohydrates during training is advisable for longer and more intensive exercise (e.g. longer runs, cycling or triathlon units) - especially if the training lasts an hour or longer.
Fast energy: which carbohydrates the body utilizes
Not all carbohydrates have the same effect on the body. Some are absorbed and utilized more quickly, others more slowly. Quickly available carbohydrates are particularly suitable for providing energy during exercise, as the body can use them to quickly replenish energy without putting unnecessary strain on the digestive system.
These include in particular
Glucose (dextrose)
Fructose (fruit sugar)
Maltodextrin (a rapidly absorbable carbohydrate mixture of glucose building blocks)
Sucrose (household sugar, consists of glucose and fructose)
How much carbohydrate can the body absorb?
The absorption capacity in the small intestine is limited, which means that not everything you consume reaches the muscles. Absorption via the glucose transport pathway is around 60 grams per hour. If fructose is also ingested, this capacity can be increased to up to 90 grams per hour - because fructose uses its own transport pathway in the intestine.
The targeted combination of different carbohydrates is therefore a sensible strategy to maximize energy intake during exercise - without risking digestive problems.
Optimal combinations for your training
Experienced athletes and studies recommend mixtures in a ratio of 2:1 (glucose to fructose) to ensure an efficient carbohydrate intake. In practice, this looks like this:
Maltodextrin : fructose (2:1)
Glucose : fructose (2:1)
Glucose : sucrose : fructose (ratio coordinated)
Advanced users can also adjust the ratio towards 1:1 if the gastrointestinal tract is well trained. It remains important: The total intake of glucose and maltodextrin should not exceed 60 g/h to avoid overloading. The additional fructose can increase the total intake to up to 90 g/h.
Fig.: The new carbohydrate intake guidelines. (Jeukendrup, 2014).
Conclusion: making clever use of carbohydrates
The targeted supply of quickly utilizable carbohydrates is a decisive factor for performance during long and intensive units. It's not just a question of "if", but above all "how much" and "which combination". With the right timing and the right mix, you can relieve your glycogen stores, delay fatigue - and improve your performance in the long term.
Source:
Jeukendrup, A. (2014). A Step lowards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. SportsMed.44 (Suppl 1) 25-33.