nutrients Review Nutrition in Ultra-Endurance: State of the Art Pantelis T. Nikolaidis 1,2 , Eleftherios Veniamakis 3, Thomas Rosemann 4 and Beat Knechtle 4,5,* 1 Laboratory of Exercise Testing, Hellenic Air Force Academy, 13671 Dekelia, Greece; [email protected] 2 Exercise Physiology Laboratory, 18450 Nikaia, Greece 3 Department of Nutrition and Dietetics, Technological Educational Institute, 72300 Sitia, Greece; [email protected] 4 Institute of General Practice and for Health Services Research, University of Zurich, 8091 Zurich, Switzerland; [email protected] 5 Medbase St. Gallen Am Vadianplatz, 9001 St. Gallen, Switzerland * Correspondence: [email protected]; Tel.: +41-(0)-71-226-93-00 Received: 18 October 2018; Accepted: 11 December 2018; Published: 16 December 2018 Abstract: Athletes competing in ultra-endurance sports should manage nutritional issues, especially with regards to energy and fluid balance. An ultra-endurance race, considered a duration of at least 6 h, might induce the energy balance (i.e., energy deficit) in levels that could reach up to ~7000 kcal per day. Such a negative energy balance is a major health and performance concern as it leads to a decrease of both fat and skeletal muscle mass in events such as 24-h swimming, 6-day cycling or 17-day running. Sport anemia caused by heavy exercise and gastrointestinal discomfort, under hot or cold environmental conditions also needs to be considered as a major factor for health and performance in ultra-endurance sports. In addition, fluid losses from sweat can reach up to 2 L/h due to increased metabolic work during prolonged exercise and exercise under hot environments that might result in hypohydration. Athletes are at an increased risk for exercise-associated hyponatremia (EAH) and limb swelling when intake of fluids is greater than the volume lost. Optimal pre-race nutritional strategies should aim to increase fat utilization during exercise, and the consumption of fat-rich foods may be considered during the race, as well as carbohydrates, electrolytes, and fluid. Moreover, to reduce the risk of EAH, fluid intake should include sodium in the amounts of 10–25 mmol to reduce the risk of EAH and should be limited to 300–600 mL per hour of the race. Keywords: cycling; fluid overload; exercise-associated hyponatremia; limb swelling; swimming; ultra-marathon 1. Introduction An ultra-endurance race may refer to running, cycling, swimming, cross-country skiing or a multi-sport event such as triathlon. The criterion to define these modes of exercise as ultra-endurance is to last at least six hours [1]. On the other side of the spectrum of duration, an ultra-endurance race may last even days or weeks. In these races, athletes usually compete for time, i.e., they attempt covering a given distance in the least time; however, other formats of races exist too, e.g., they might compete for distance where they aim to cover a maximum distance for a given time (e.g., 12 h run). Considering the long duration of these races, an ultra-endurance athlete faces sport-specific nutritional issues. A major nutritional concern is the high energetic demands accompanying the physiological stress of exercise. Ultra-endurance exercise induces an energy deficit (negative energy balance, i.e., energy expenditure outscores energy intake), which in turn may lead to an energy depletion [2]. The increased exercise metabolism induces heat production triggering sweating rates at a risk of hypohydration (2%–5% of body water loss). In this case, hydration should be optimized in order to avoid medical Nutrients 2018, 10, 1995; doi:10.3390/nu10121995 www.mdpi.com/journal/nutrients Nutrients 2018, 10, x FOR PEER REVIEW 2 of 17 hypohydration (2%–5% of body water loss). In this case, hydration should be optimized in order to Nutrients 2018, 10, 1995 2 of 17 avoid medical issues, such as hyponatremia and heat illness [3]. 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Accordingly,interest in these only sports a few remains reviews relatively have been small ever with conducted regards on to nutrition other sports and [ 5ultra-endurance,6]. 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Therefore,original articles the aim in of this the presenttopic focusing study was on to energy review alldeficit published and dysregulation original articles of influid this metabolismtopic focusing (Figure on energy 1). deficit and dysregulation of fluid metabolism (Figure1). # Figure 1. MainMain nutritional nutritional aspects in ultra-endurance. = decrease. decrease. 2. Energy Deficit 2. Energy Deficit The energy balance refers to the difference between energy expenditure and energy intake [9–11]. The energy balance refers to the difference between energy expenditure and energy intake [9– In turn, the energy expenditure is assessed using triaxial accelerometry [10], indirect calorimetry [12] or 11]. In turn, the energy expenditure is assessed using triaxial accelerometry [10], indirect calorimetry the energy equivalent of oxygen that can be calculated from heart rate recordings during the race [9,11]. [12] or the energy equivalent of oxygen that can be calculated from heart rate recordings during the Energy intake is estimated by nutritional analysis of all drinks and foods contents consumed during a race [9,11]. Energy intake is estimated by nutritional analysis of all drinks and foods contents race [9,10,12]. consumed during a race [9,10,12]. 2.1. Energy Balance in Race 2.1. Energy Balance in Race The long duration of an ultra-endurance race implies increased exercise-induced energy expenditureThe long [13 duration]. To balance of an the ultr increaseda-endurance energy race expenditure, implies increased an optimal exercise-induced nutrition should energy ensure expenditureadequate energy [13]. To intake balance [14]. the So increased far, research energy has expenditure, concluded that an optimal endurance nutrition and ultra-endurance should ensure adequateathletes do energy not consume intake [14]. sufficient So far, food research and drinks has concluded resulting inthat a negative endurance energy and and ultra-endurance fluid balance during the race, as shown by their reduced post-race body mass and body fat percentage [15,16]. Nutrients 2018, 10, x FOR PEER REVIEW 3 of 17 Nutrients 2018, 10, 1995 3 of 17 athletes do not consume sufficient food and drinks resulting in a negative energy and fluid balance during the race, as shown by their reduced post-race body mass and body fat percentage [15,16]. For Forexample, example, a 54-km a 54-km mountain mountain ultra-marathon ultra-marathon induced induced a negative a negative energy energy balance balance of ~3700 of ~3700 kcal [17]. kcal In [17 ]. Inaddition, addition, a anegative negative energy energy balance balance might might be be re relatedlated to to other other undesired undesired nutritional nutritional practice practice and