Carbohydrates are the most important macronutrient for the performance of endurance athletes. They provide the main source of energy when exercise duration lasts for greater than a few seconds. Stored muscle glycogen and blood glucose are the most important substrates for contracting muscle (both of which are maintained through the consumption of carbohydrates) . Low glycogen concentrations lead to reduced high-intensity performance and less time to fatigue . To maintain these energy stores, it is recommended that endurance athletes consume between 6-12 grams of carbohydrates per kg of body weight, per day, preferably from quality sources such as whole grains, vegetables, and fruits , .
The timing of carbohydrate ingestion can also play an important role during endurance exercise itself. For example, it is recommended that athletes consume 1-4 grams of carbohydrates per kg of bodyweight, 1-4 hours before competition to ensure glycogen stores are full . This helps to ensure that energy stores last as long as possible before reaching fatigue.
Carbohydrates can also be utilised within exercise itself. This is because their consumption can provide a fuel source for the muscle as glycogen stores are depleted . It is generally recommended that during exercise bouts of 1-2.5 hours, athletes consume between 30-60 grams of carbohydrates per hour, as uptake is limited to around one gram per minute by cellular digestive and transport systems .
Finally, post-exercise, it is recommended that you ingest 1-1.2 grams of carbohydrates per kg of body weight to optimise muscle glycogen resynthesis. This reduces fatigue and allows the body to recover for the next session. Prolonged depletion of carbohydrates can impair immune function, reduce training output, and cause burnout .