For a race to be considered ultra-endurance it must last more than 4 hours, although sometimes they are only considered if lasting beyond 6 hours. These races can last for days, or even weeks, with energy requirements as high as 7000 kilocalories per day. A negative energy balance can lead to energy depletion, with a decrease of the levels of body fat and skeletal muscle mass, with sport anaemia, gastrointestinal discomfort and hypohydration also being noted as key factors in the performance.
Inadequate nutrition might impair performance, with energy deficit affecting finish times in many ultra-endurance events. For a 24 hours race the decrease of body mass reported was 1.7%, a combination of fat mass, skeletal muscle mass and fluid loss, especially located in the lower trunk.
Carbohydrates are usually the main source of energy, with an average of 68% in ultra-endurance events, although their contribution can be modified, especially in cold conditions, like in an 800k Antarctic race, where fat can be contributing a 60% to the energy expenditure and carbohydrates only a 25%. The consumption can go to 90g of carbohydrates per hour of exercise for ultra-endurance athletes, compared with the 60g/h of endurance athletes.
The first carbo-loading protocol, aimed to load the body glycogen stores (liver and muscles), was developed in the 1960s. It consisted of a 3-4 days “depletion phase”, with high-intensity exercise and low carbohydrates intake, and a 3-4 days “loading phase”, with low-intensity exercise and high-carbohydrates diet. This classic protocol was later modified to a 6-days period, with progressive increase in the carbohydrates intake accompanied by a decrease in physical activity. This shorter protocol avoided fatigue in the stressful depletion phase. The most recent approach favours the combination of a resting period rest of up to three days with a high carbohydrates diet.
In ultra-endurance sports fat is a reliable source of energy. The “fat-adaptation” diets are aimed to increase the oxidation of fatty acids and attenuate glycogen depletion, in what is known as “ketogenic adaptation”. They provide 60-70% of energy from fat, and only a 15-20% from carbohydrates, and are followed for the last 5-10 days before the race. As intensity in these competitions is always sub-maximal the high levels of at would not be detrimental.
Amino acids are the building blocks of proteins, and it is still unclear if their consumption has any effect on skeletal muscle damage. On the other side, the intake of more than 2g of protein per kilogram of weight per day didn´t have any influence on physical performance.
It is clear that maintaining hydration levels is important to keep aerobic performance. Hypohydration decreases performance, increasing body temperature, heart rate, and the use of carbohydrates as fuel source. Common recommendations for proper hydration, trying to avoid losses over 2% of body mass, are usually suitable for shorter periods of exercise but sometimes inappropriate for ultra-endurance activities, often resulting in hyperhydration.
Previous recommendations disqualifying “thirst” as a stimulus “to drink” originated in conditions where hypohydration would develop rapidly, usually in high sweating rates and high intensity exercise. Nowadays the concept of “drinking to thirst” is adequate for ultra-endurance activities, even in hot conditions. Several studies have reported that this level of drinking doesn´t affect negatively performance in comparison with higher volumes of liquid uptake.
Excessive fluid intake (overload), or hyperhydration, may be associated with an increase in body mass, total body water, and a decrease in plasma sodium concentrations, a condition called hyponatraemia, which can develop serious complications. The hyponatraemia is common among endurance athletes, with more prevalence in female and slower athletes, and although is present in ultra-running and ultra-swimmimg, is usually absent in ultra-cycling, probably because cyclists can drink from their bottles as they wish. Excessive sodium intake is unnecessary, and potentially harmful.
Proper nutrition will delay fatigue and hydration will support body functions, maintaining exercise performance during ultra-endurance events, and by extension in your life.
Nutrition in Ultra-Endurance: State of the Art.
Nikolaidis PT, Veniamakis E, Rosemann T, Knechtle B.
Nutrients. 2018 Dec 16; 10(12). doi: 10.3390/nu10121995.
Considerations for ultra-endurance activities: part 1- nutrition.
Costa RJS, Hoffman MD, Stellingwerff T.
Res Sports Med. 2018 Jul 28:1-16, doi: 10.1080/15438627.2018.1502188
Considerations for ultra-endurance activities: part 2 – hydration.
Hoffman MD, Stellingwerff T, Costa RJS.
Res Sports Med. 2018 Jul 28:1-13, doi: 10.1080/15438627.2018.1502189