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  • Writer's pictureTristan

Incredible ultra-endurance achievements


Humans were originally adapted to perform extremely long and sustained physical activities as they had to hunt to feed themselves and survive. Throughout time, humans became more and more sedentary as everything became easily available (clean water, supermarkets, transport). However, some people test their limits by participating in ultra-endurance races. If you thought that a marathon was long, it is nothing compared to the length of these events. The effort is sustained for at least 4h in these races (compared to 2h for a marathon) and can comprise important elevation changes as well as be in extreme environments (warm/cold, mountains, desert, high altitude…). As a result, it requires participants to have a high physical condition, important specific training, as well as a well-prepared race strategy.

Different factors leading to fatigue:

During these long events, nothing can be taken lightly as any mistake is multiplied due to the length of the race. Fatigue is multifactorial in these events and everything needs to be accounted for to maximise the final performance. The main reasons for the decreased performance were found to be central fatigue (linked to the brain), peripheral fatigue (linked to the muscles), thermic stress, dehydration, and decreased glycogen stores. In some instances, additional constraints are added such as important loads to carry (equipment, food, clothing), and needs to be accounted for the total fatigue generated. Fortunately, these factors negatively impacting endurance performance can be altered to negate their effects. We will mainly cover the role of nutrition in altering the negative effects.

How to maximise performance:

Many athletes, unfortunately, have to withdraw from races or underperform due to their nutrition. It is often due to a lack of nutrition education and knowledge. It can also be due to other constraints such as the non-availability of food, digestive discomfort, appetite loss, and others. By understanding the principal causes, it is possible to implement strategies to perform at your best.

1) The important value of carbohydrates

First of all, education is key. If you don’t understand how your nutrition can alter your sports performance, it will be difficult to follow a good diet to maximise your performance. One of the steps is therefore to understand how the energy is produced during endurance performance. Due to moderate intensity in endurance sports, a lot of the energy produced comes from fat stores, which is convenient as being the most abundant stores in our body. However, carbohydrates are also used and as our body stores are smaller compared to fat stores, it can become a limiting factor. Hence it is required to maintain a regular carbohydrate intake during the effort. Intakes around 75-90g/h were found to be the most efficient for endurance performance. It should also be highlighted that at this intake rate, it is required to take multiple sources of carbohydrates to be able to absorb them. Studies found that a mix with 2/3 of glucose and 1/3 of fructose was the most efficient (60g of glucose and 30g of fructose for example).

2) Ketogenic diet

Some studies found that ultra-endurance athletes could benefit from being keto-adapted which means that their metabolism uses mainly fat stores instead of carbohydrates during low/moderate intensity efforts which allows them to keep their carbohydrate stores filled for longer. This change in metabolism was observed after following a ketogenic diet (mainly including dietary fats, and proteins as well as containing less than 50g of carbohydrates per day) over 2-3 weeks, as well as performing training with low carbohydrate stores.

3) Protein intakes

Throughout the training cycle and evolution of endurance athletes, protein intakes are important all year round to support muscle development and maximise recovery. The recommended intake is 1.5-1.8g/kg/jour (105-126g/day for a 70kg athlete). However, when accounting for the sustained efforts performed, intakes above 2g/kg/day could be needed.

4) The intestinal microbiota complexes

We now know that our microbiota is impacted by physical activity due to increased oxidative stress, intestinal permeability, electrolyte imbalance, decreased glycogen stores, and other reasons. Moreover, the microbiota can affect our sports performance through the metabolic advantage given, the modulation of the immune system, the regulation of gastrointestinal health as well as the reversion of the inflammatory response post-exercise. Due to the important prevalence of gastrointestinal symptoms when performing ultra-endurance sports (60-96%), it is critical to adapt the race or training strategy accordingly. Symptoms can be due to the environment, the different foods ingested, as well as medical predispositions or conditions. To avoid unpleasant surprises during the race, it is required to try the race strategy during training to ensure the body can tolerate it as it could be counterproductive if it impacts the performance negatively. Additionally, studies found positive results for the use of probiotics on gastrointestinal symptoms as well as post-exercise recovery. Therefore, they can be used by athletes who suffer from these problems.

5) The role of hydration

Hydration is often taken for granted but it is critical as dehydration of more than 5% loss of body weight can lead to a 30% decrease in performance. However, drinking too much liquid can also lead to gastric discomfort so the right balance needs to be found depending on the intensity of the exercise as well as the environment. For example, in warm weather, more liquid is needed to replace the losses and it should be cold.

6) FODMAP diet

Recently, some studies focused on diets low in FODMAP. Some carbohydrate groups are less easily digestible than others, they are called FODMAP. Low FODMAP diets mainly remove legumes, processed meats, as well as some fruits and vegetables. It would appear that decreasing FODMAPs (7g/day instead of 40g/day) would reduce gastrointestinal discomfort during training and races.


Athletes taking part in ultra-endurance sports should understand the different factors leading to fatigue to maximise their performance. Everything should be carefully examined as it could lead to withdrawal. The main aspects to focus on are carbohydrate intakes, hydration, probiotics intake, the option to follow a ketogenic diet for 2-3 weeks preceding the race, specific physical training supported by tailored nutrition, and optimising the race nutrition strategy by trying it during training.


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