Nutrition in ultra-endurance racing-aspects of energy balance, fluid balance and exercise-associated hyponatremia.
An ultra-endurance performance is defined as an endurance performance lasting for six hours or more (1). The most popular ultra-endurance disciplines are swimming, cycling, running and triathlon as the combination of these three disciplines. Table 1 summarizes well-known ultra-endurance races. When ultra-endurance athletes compete for hours, days or even weeks, they face different problems regarding nutrition such as dehydration, glycogen depletion, gastrointestinal discomfort and fluid overload, which may occur as a single problem or a combination of problems. The continuous physical stress leads to an energy deficit. Furthermore, the ultra-endurance performance may lead to dehydration due to sweating.
Table 1. Well-known ultra-endurance races in swimming, cycling, running and triathlon Discipline Distance Website Swimming Channel ~34 km, sea www.dover.uk.com/channelswimming Swimming water Cycling Furnace Creek ~820 km in www.adventurecorps.com 508 California, USA Tortour ~1,000 km www.tortour.ch around Switzerland Race around ~2,200 km www.racearoundireland.com Ireland around Ireland Race around ~2,200 km www.racearoundaustria.at Austria around Austria Race across ~4,800 km www.raceacrossamerica.org America across America Running Ultra Trail 166 km www.ultratrailmb.com du Mont Blanc Badwater 217 km www.bardwater.com Spartathlon 246 km www.spartathlon.gr Marathon des ~240 km www.darbaroud.com Sables Western 161 km www.ws100.com States Endurance Run Trans Europe ~5,100 km www.transeurope-footrace.org Foot Race Triathlon Virgina 7.6 km swim, www.usaultratri.com Double Iron 360 km bike, Triathlon 84.4 km run Virgina 11.4 km swim, www.usaultratri.com Triple Iron 540 km bike, Triathlon 126.6 km run Deca Iron 36 km swim, www.multisport.com.mx Triathlon 1,800 km Mexico bike, 420 km run
Literature regarding nutrition in endurance and ultra-endurance has already been reviewed for specific topics (1-8). In these reviews, recommendations were made for nutritional practices in order to recover and prepare for daily training (1),(6),(7), protein intake during training (6),(8), intake of fat prior to an endur-ance performance (3), intake of carbohydrates before performance (2), (4), (6), (8-10), intake of carbohydrates during exercise (3), (4), (6), (10), (11), intake of carbohydrates after performance (4), (6), (10-12), protein intake for recovery (10), and fluid intake during performance (4-8), (10), (11), (13), (14).
However, the problems of energy deficit and fluid metabolism in ultra-endurance athletes have not been addressed. The main problems regarding energy and fluid metabolism of an ultra-endurance performance can be separated in two categories. The first aspect concerns the energy deficit with the corresponding loss in solid body masses such as fat mass and skeletal muscle mass. The second aspect concerns the deregulation of fluid metabolism with dehydration or fluid overload with an increased risk of exercise-associated hyponatremia (EAH). The aim of this review is to focus on the decrease in body mass, and the problems in energy and fluid balance ultra-endurance performance.
Nutritional problems associated with ultra-endu-rance performance
Energy turnover and energy deficit in ultra-endurance
Most research conducted on extreme endurance (>3 hours) is based on case studies and studies involving a small number of individuals (5). Con-ducting research in these events is challenging and the number of studies is very limited. Due to the lack of research and the complexities in conducting research in ultra-endurance races, we are dependent on scientific findings from other similar endurance sports. Thus findings for nutrition in endurance performance shorter than six hours in duration are examined first. For endurance exercise lasting 30 min or more, the most likely contributors to fatigue are dehydration and carbohydrate depletion (7), whereas gastrointestinal problems, hyperthermia, and EAH can reduce endurance exercise performance and are potentially health threatening, especially in events of four hours or longer in duration (7), (15). Gastrointestinal problems occur frequently, especially in long-distance triathlons (15). Problems seem to be related to the intake of highly concentrated carbohydrate solutions, or hyperosmotic drinks, and the intake of fibers, fat and protein (15).
Meeting macronutrient and fluid intake demands is of highest priority for ultra-endurance athletes (4). An ultra-endurance athlete competing for hours or days with or without breaks expends considerable amounts of energy (16-37). Meeting the energy demands of ultra-endurance athletes during racing requires careful planning and monitoring of food and fluid intake (25), (38). Adequate carbohydrate and fluid intake during an endurance performance may help to reduce fatigue and enhance performance (10). Current evidence continues to support mandatory high carbohydrate intakes before an event to maximize muscle glycogen stores and during an event to prevent hypoglycemia (4). Numerous case reports (17), (25), (28-34), (39) and field studies (19), (24), (27), (40-44) showed, however, that ultra-endurance athletes were unable to self-regulate diet or exercise intensity to prevent a negative energy balance. Estimation of energy expenditure prior to the beginning of an ultra-endurance event would allow athletes to plan the diet energy intake better (44). Furthermore, the insufficient energy intake is associated with malnutrition such as a low antioxidant vitamin intake (45).
Adequate food and fluid intake is related to a suc-cessful finish of an ultra-endurance race (24), (46), (47). An important key to a successful finish in an ultra-endurance race seems to be an appropriate nutri-tion strategy during the race (47). Additionally, an energy deficit inhibits ultra-endurance performance. A significant negative relationship between energy intake and time taken to complete a 384-km cycle race is documented in ultra-cyclists (43). An ultra-endurance performance results in an energy deficit (17), (19-31), (34), (36-39), (48-55).There are reports of energy expenditures of ~365-750 kcal/hour with total energy expenditures of ~18 000-80 000 kcal, which were required to complete adventure races. These energy expenditures were accompanied by significant negative energy balances during competitions (8).
In Table 2, results from case and field studies are summarized and separated by discipline (i.e. swimming, cycling, running and the combination as triathlon). Regarding the single disciplines, the energy deficit seems higher in swimming compared to cycling and running. This might be explained by the different environment (i.e. water) as compared to cycling and running. Alternatively, swimming may involve more skeletal muscle mass than cycling or running. Or it could be that swimmers ingest fewer calories during performance than runners or cyclists do. For events lasting 24 hours or longer, the energy deficit is highest
Table 2. Energy balance in ultra-endurance athletes in different disciplines Distance and/or Subjects Total Total Total Energy time energy ener- energy deficit intake gy deficit in (kcal) expendi- (kcal) 24 hours ture (kcal) (kcal) Swimming 26.6 km 1 male 2,105 5,540 - 3,435 26.6 km 1 male 24-h swim 1 male 3,900 11,460 - 7,480 - 7,480 Mean (SD) Cycling 12 hours 1 male 2,750 5,400 - 2,647 indoor-cycling 557 km in 24 1 male 5,571 15,533 - 9,915 - 9,915 hours 617 km in 24 1 male 10,000 13,800 - 3,800 - 3,800 hours 694 km in 24 1 male 10,576 19,748 - 9,172 - 9,172 hours 24 hours cycling 6 males 8,450 18,000 - 9,590 - 9,590 1,000 km in 48 1 male 12,120 16,772 - 4,650 - 2,325 hours 1,126 km in 48 1 male 11,098 14,486 - 3,290 - 1,645 hours 2,272 km in 5 d 7 1 male 51,246 80,800 - 29,554 - 5,585 h 4,701 km in 9 d 1 male 96,124 179,650 - 83,526 - 8,352 16 h Mean (SD) - 6,298 [+ or -] 3,392 Running 160 km in 20 h 1 male 9,600 8,480 - 1,120 320 km in 54 h 1 male 14,760 18,120 - 3,360 - 1,493 501 km in 6 days 1 male 39,666 54,078 - 14,412 - 2,402 Atacama crossing 1 male 37,191 101,157 - 63,966 - 3,046 100 km 11 female 570 6,310 - 5,750 100 km 27 male 760 7,420 - 6,660 Mean (SD) - 2,313 [+ or -] 780 Triathlon Triple Iron 1 male 15,750 27,485 - 11,735 - 6,869 ultra-triathlon Triple Iron 1 male 22,500 28,600 - 6, 100 - 3,404 ultra-triathlon Gigathlon 1 male 38,676 59,622 20,646 - 9,937 multi-stage triathlon 10 x Ironman 1 male 77,640 89,112 - 11,480 - 7,544 triathlon Mean[+ or -]SD - 6,938 [+ or -] 2,699 Distance and/or Energy Refe- time deficit rence per hour (kcal) 26.6 km - 429 30 26.6 km - 500 48 24-h swim - 311 49 Mean (SD) - 413[+ or -]95 12 hours - 220 34 indoor-cycling 557 km in 24 - 413 39 hours 617 km in 24 - 158 28 hours 694 km in 24 - 382 25 hours 24 hours cycling - 399 26 1,000 km in 48 - 96 36 hours 1,126 km in 48 - 65 50 hours 2,272 km in 5 d 7 - 232 17 h 4,701 km in 9 d - 360 22 16 h Mean (SD) - 258 [+ or -] 134 160 km in 20 h - 56 51 320 km in 54 h - 62 23 501 km in 6 days - 100 21 Atacama crossing - 127 37 100 km - 452 52 100 km - 580 53 Mean (SD) - 229 [+ or -] 227 Triple Iron - 286 54 ultra-triathlon Triple Iron - 141 31 ultra-triathlon Gigathlon - 414 29 multi-stage triathlon 10 x Ironman - 314 55 triathlon Mean[+ or -]SD - 288 [+ or -] 112
in multi-sports disciplines and cycling. In running, the energy deficit is approximately three times lower than it is in both triathlon and cycling.
Change in body mass during an ultra-endurance performance
A further important fact in ultra-endurance racing is the finding that an ultra-endurance performance generally results in a loss in body mass (Table 3) (17), (21-23), (25), (27), (28), (31), (35-37), (48), (49), (52), (54), (55-68). The loss in body mass occurs most often in the lower trunk (21), (37), (60). Depending on the length of the endurance performance and the discipline, the decrease in body mass corresponds to a decrease in fat mass (17), (23), (26), (33), (34), (55), (56), (62-67) and/or skeletal muscle mass (17), (24), (32), (55), (56), (58), (59), (61), (62), (66).
Table 3. Change in body composition in ultra-endurance athletes in different disciplines Distance and/or Subjects Change in Change Change Change time body mass in in in (kg) fat muscle body mass mass water (kg) (kg) (l) Swimming 24-h swim 1 male - 1.6 - 2.4 - 1.5 - 3.9 12-h swim 1 male - 1.1 - 1.1 Cycling 12-h indoor 1 male - 0.4 - 0.9 + 0.2 cycling 617 km in 24 1 male + 4.0 + 0.9 + 2.9 hours 1,000 km within 1 male + 2.5 - 1 + 0.4 + 1.8 48 hours 2,272 km in 5 d 1 male - 2.0 - 0.79 - 1.21 7 h 4,701 km in 9 d 1 male - 5 - - 16 h Running 12-h run 1 male + 1.5 - 4.4 + 1.0 + 4.9 320 km in 54 h 1 male - 0.4 - 0.3 - 1.0 501 km in 6 1 male - 3.0 - 6.8 days 100 km in 762 11 - 1.5 + 2.2 min females 100 km in 11:49 39 males -1.6 - 0.4 - 0.7 + 0.8 h:min 338 km in 5 21 males - 0.6 days 1,200 km in 17 10 males -3.9 - 2.0 + 2.3 days l Triathlon Triple Iron 1 male - 1.1 - 0.4 + 1.4 + 2.0 ultra-triathlon in 41 h Triple Iron 1 male + 2.1 + 0.4 + 4.4 ultra-triathlon in 43 h Deca Iron 1 male + 3.2 + 2.4 + 2.4 ultra-triathlon Quintuple Iron 1 male - 0.3 - 1.9 + 1.5 ultra-triathlon 10 x Ironman 1 male - 1.0 - 0.8 - 0.9 + 2.8 triathlon in 128 h Ironman in 11 h 27 males - 1.8 - 1.0 36 min Triple Iron 31 males - 1.7 - 0.6 - 1.0 ultra-triathlon 10 x Ironman 8 males - 3 triathlon in128 h Mean[+ or -]SD - 0.4 [+ - 1.4 + 0.1 + 1.5 or -] 2.5 [+ or [+ or [+ or -] 2.3 -] 1.9 -] 1.30 Distance and/or Reference time 24-h swim 49 12-h swim 48 Cycling 12-h indoor 34 cycling 617 km in 24 28 hours 1,000 km within 36 48 hours 2,272 km in 5 d 17 7 h 4,701 km in 9 d 22 16 h 12-h run 57 320 km in 54 h 23 501 km in 6 21 days 100 km in 762 52 min 100 km in 11:49 56 h:min 338 km in 5 59 days 1,200 km in 17 58 days Triple Iron 54 ultra-triathlon in 41 h Triple Iron 31 ultra-triathlon in 43 h Deca Iron 60 ultra-triathlon Quintuple Iron 35 ultra-triathlon 10 x Ironman 55 triathlon in 128 h Ironman in 11 h 61 36 min Triple Iron 62 ultra-triathlon 10 x Ironman 63 triathlon in128 h Mean[+ or -]SD
The total amount of amino acid oxidation during endurance exercise is only 1-6% of the total energy cost of exercise (69). The decrease in skeletal muscle mass due to protein degradation is most probably very low. Concentric endurance performance, such as cycling, results in a decrease in fat mass (34), (65), whereas an eccentric endurance performance, such as running, results in a decrease in muscle mass (59).
In runners, a decrease in both fat mass and skeletal muscle mass has been reported (58), (59). For swim-mers, no change in body mass, fat mass or skeletal muscle mass has been reported for 12-hour indoor pool swimmers (70). In male open-water ultra-swimmers, however, a decrease in skeletal muscle mass was observed (71).
However, also an increase in body mass can occur during an ultra-endurance performance (Table 3) (28), (31), (36), (57), (60). Additionally, an increase in skeletal muscle mass has also been reported (28), (31), (34), (36), (54), (57), (60). The increase in body mass was most probably due to fluid overload. An increase in estimated skeletal muscle mass might occur in cases where anthropometric methods were used and an increase in skin-fold thicknesses and limb circumferences was measured. Overall, ultra-endurance athletes seemed to lose approximately 0.5 kg in body mass and approximately 1.4 kg in fat mass where skeletal muscle mass seemed to remain largely unchanged. Additionally, total body water seemed to increase by approximately 1.5l (35), (36), (52), (54-58).
Dehydration, fluid intake and fluid overload
Dehydration refers both to hypohydration (i.e. dehydration induced prior to exercise) and to exercise-induced dehydration (i.e. dehydration that develops during exercise). The latter reduces aerobic endurance performance and results in increased body temperature, heart rate, perceived exertion, and possibly increased reliance on carbohydrates as a fuel source (72). Most endurance athletes are concerned with dehydration during an ultra-endurance performance. Generally, ultra-endurance athletes do not meet their fluid demand during exercise (5). It has been shown that body mass was lost during a 24-hour ultra-marathon (73). However, body mass loss in ultra-endurance athletes seems to be due to a decrease in sold mass and not dehydration (62), (64), (74). Endurance athletes should attempt to minimize dehydration and limit body mass losses due to sweating to 2-3% of body mass (7). Adequate fluid intake prevents loss in body mass (41). How-ever, fluid overload may lead to an increase in body mass (75) and a decrease in plasma sodium (75) with the risk of EAH (75-77).
Recent trends towards excessive fluid intake have resulted in frequent reports of hyponatremic hyper-hydration in ultra-distance athletes, with a greater incidence in women than in men (4). Fluid overload may lead to a considerable increase in body mass (75). For example, one athlete competing in a Deca Iron ultra-triathlon with 38km of swimming, 1,800km of cycling and 422 km of running in 12 d 20 h showed an increase in body mass of 8kg within the first three days (60). Unfortunately, energy intake, energy expenditure and fluid intake were not recorded, but the changes in skinfold thickness showed that edemas during the race had occurred. In athletes with post-race increases in body mass, increased skin-fold thicknesses and limb circumferences of the lower limb were also recorded (36), (60). In an athlete with an increase in body mass, an increase in skin-fold thicknesses at four skin-fold sites was also reported (28). Both of these races were held in rather hot environments where most probably fluid intake was rather high.
However, in athletes with decreases in body mass, an increase in lower limb skin-fold thicknesses has also been reported (17), (55), (67). In one athlete with a decrease in body mass after a Triple Iron ultra-triathlon, a con-siderable swelling of the feet was reported (54). The timing in measuring skin-fold thicknesses and limb circumferences post-race is important because body mass and total body water may increase days after the race is finished (54).
The increase in body mass, skin-fold thicknesses and limb circumferences was most probably due to an increase in total body water (Table 3) (36), (55), (78). An increase in total body water has been reported in ultra-endurance athletes (35), (36), (52), (54-58), (63), (79), (80). The question is why both the skin-fold thicknesses and total body water increased. The increase in total body water might be due to an increase in plasma volume (35), (79-82), which in turn might be due to sodium retention (79), (81) due to increased activity of aldosterone (35), (83). An association between an increase in plasma volume and an increase in the potassium-to-sodium ratio in urine might suggest that the increased activity of aldosterone (84) may result in retention in both sodium and fluid during an ultra-endurance performance (53). In a multi-stage race over seven days, total mean plasma sodium con-tent increased and was a major factor in the increase in plasma volume (79).
Apart from these pathophysiological aspects, fluid overload might also result in an increase in limb volume. A recent study showed a relationship between changes in limb volumes and fluid intake (85). Since neither renal function nor fluid regulating hormones were associated with changes in limb volumes, fluid overload is the most likely reason for an increase in both body mass and limb volumes. An actual study showed an association between an increased fluid in-take and swelling of the feet in ultra-marathoners (86).
Fluid intake and exercise-associated hyponatremia (EAH)
Fluid overload during an endurance performance might lead to exercise-associated hyponatremia (EAH), defined as a serum sodium concentration ([Na.sup.+]) <135 mmol/l during or within 24 hours of ex-ercise (87). EAH was first described in the literature in 1985 by Noakes et al. where ultra-marathoners in South Africa with hyponatremia were thought have had 'water intoxication'(88). Three main factors are responsible for the occurrence of EAH in endurance athletes: (i) overdrinking due to biological or psychological factors; (ii) inappropriate secretion of the antidiuretic hormone (ADH), in particular, the failure to suppress ADH-secretion in the face of an increase in total body water (TBW); and (iii) a failure to mobilize [Na.sup.+] from the osmotically inactive sodium stores or alternatively inappropriate osmotic inactivation of circulating [Na.sup.+] (87). In that the mechanisms causing factors (i) and (iii) are unknown, it follows that the prevention of EAH requires that athletes be encouraged to avoid over-drinking while exercising.
EAH is the most common medical complication of ultra-distance exercise and is usually caused by excessive hypotonic fluid intake (89), (90). The main reason for developing EAH is the tendency of overdrinking during an endurance performance, by either an excessive fluid consumption (76) and/or inadequate sodium intake (91). Subjects developing EAH during an ultra-endurance performance consumed twice as much fluid as those subjects without EAH (76). Generally, fluid overload is reported for slower athletes (92). However, in ultra-endurance athletes, faster athletes drink more than slower athletes but did not develop EAH (93), (94).
The environmental conditions seemed to influence the prevalence of EAH. EAH was a common finding in ultra-endurance races held in extreme cold (91), (95) or extreme heat (75), (96). In temperate climates, EAH was, however, relatively uncommon (83), (97-110). There seemed to be a gender difference where females seemed to be at higher risk for EAH (95). The prevalence of EAH in ultra-marathoners (101), (110), (114) was, however, not higher compared to marathoners (92), (111-113).
The prevalence of EAH seemed also to be dependent on the discipline (Table 4). While EAH was highly prevalent in ultra-swimming (95) and ultra-running (96), the prevalence of EAH was low (99), (115) or even absent (98), (100) in ultra-cyclists. In addition, the length of an ultra-endurance race seemed to increase the risk for EAH. The highest prevalence of EAH has been found in Ironman triathlons (106), (108), Triple Iron ultra-triathlons (109) and ultra-marathons over 161 km (75), (96).
Table 4. Prevalence of exercise-associated hyponatremia in ultra-endurance athletes in different disciplines Distance and/or Conditions Subjects Prevalence of time exercise-associated hyponatremia Swimming 26-km open-water Moderate 25 males and 11 8 % in males and 36% ultra-swim females in females Cycling 665-km mountain Moderate 25 cyclists 0 % bike race 109 km cycle Moderate 196 cyclists 0.5 % race 720-km Moderate 65 males 0 % ultra-cycling race Running 161-km mountain Hot 45 runners 51 % trail run 161-km mountain Hot 47 runners 30 % trail run 60-km mountain Moderate 123 runners 4 % run 100-km Moderate 50 male runners 0 % ultra-marathon 100-km Moderate 145 male runners 4.8 % ultra-marathon 24-hour Moderate 15 males 0 % ultra-run 90-km Moderate 626 runners 0.3 % ultra-marathon 160-km trail Hot 13 runners 0 % race Multi-disciplines 100-mile Cold 8 cyclists and 8 44 % Iditasport runners ultra-marathon 161-km race Cold 20 athletes 0 % Kayak, cycling Moderate 48 triathletes 2 % and running Ironman Moderate 330 triathletes 1.8 % triathlon Ironman Moderate 330 triathletes 18 % triathlon Ironman Moderate 95 triathletes 9 % triathlon Ironman Moderate 18 triathletes 28 % triathlon Triple Iron Moderate 31 triathletes 26 % ultra-triathlon Distance and/or Reference time 26-km open-water 95 ultra-swim Cycling 665-km mountain 98 bike race 109 km cycle 99 race 720-km 100 ultra-cycling race 161-km mountain 75 trail run 161-km mountain 96 trail run 60-km mountain 101 run 100-km 83 ultra-marathon 100-km 94 ultra-marathon 24-hour 102 ultra-run 90-km 88 ultra-marathon 160-km trail 41 race 100-mile 91 Iditasport ultra-marathon 161-km race 103 Kayak, cycling 104 and running Ironman 105 triathlon Ironman 106 triathlon Ironman 107 triathlon Ironman 108 triathlon Triple Iron 109 ultra-triathlon
Nutritional aspects during ultra-endurance racing
Guidelines for nutrition strategies for ultra-endurance races are absent since there has been very little research into optimal nutritional practices in extreme sporting events. The few investigations that have indeed been conducted have mainly been case studies. No controlled studies linking specific nutritional strategies with higher performances do exist. The comprehensive nutritional analyses of the intake patterns of ultra-endurance athletes who manage to avoid health difficulties, such as gastrointestinal distress and mental disorientation commonly associated with ultra-distance efforts have yet to be compared to the nutrient and fluid intakes of ultra-athletes who fall prey to these problems. Adequate energy and fluid intake is needed to successfully compete in an ultra-endurance race (116-124). Most studies are descriptive in nature and reporting the distribu-tion of carbohydrates, fat and protein the athletes ingested (Table 5) (17), (21), (22), (28), (29), (31), (116), (119), (120). Some studies report on the kind of food consumed (121-123) and some studies investigated the aspect of supplements (125-128).
Table 5. Intake of energy in ultra-endurance athletes in different disciplines Distance and/or Subjects Intake of Intake Intake of time (%) carbohydrates of protein (%) (%) fat Cycling 617 km in 24 1 male 64.2 27 8.8 hours 2,272 km in 5 d 7 1 male 75.4 14.6 10.0 h 4,701 km in 9 d 1 male 75.2 16.2 8.6 16 h Running 100 km 7 males 88.6 6.7 4.7 501 km in 6 days 1 male 40.0 34.6 25.4 1,005 km in 9 1 male 62 27 11 days Triathlon Deca Iron 1 male 67.4 15.6 17.0 ultra-triathlon Gigathlon 1 male 72 14 13 Triple Iron 1 male 72 20 8 ultra-triathlon Mean (SD) 68.5 [+ or -] 19.5 [+ 11.8 [+ 13.2 or -] or -] 8.5 6.1 Distance and/or Reference time (%) 617 km in 24 28 hours 2,272 km in 5 d 7 17 h 4,701 km in 9 d 22 16 h 100 km 119 501 km in 6 days 21 1,005 km in 9 122 days Deca Iron 120 ultra-triathlon Gigathlon 29 Triple Iron 31 ultra-triathlon Mean (SD)
Intake of carbohydrates
Carbohydrates are the main source of energy intake for ultra-endurance athletes (17), (38), (55), (118). When the intake of carbohydrates, fat and protein during ultra-endurance racing was analyzed for ultra-endurance athletes, the highest percentage was found in carbohydrates. Ultra-endurance athletes consume approximately 68% of ingested energy as carbohydrates (Table 5).
Intake of fat
An increased fat intake pre-race leads to an in-crease in intramyocellular lipids in ultra-endurance athletes (31). Increased intramyocellular lipids might improve ultra-endurance performance. However, field studies with controlled data do not exist with regard to whether fat loading improves ultra-endurance performance. In a case report, the ultra-endurance performance of a rower was enhanced after following a high fat diet for 14 d (129). An increased fat intake during an ultra-endurance competition might well improve performance. However, also for this conclusion, field studies with controlled data do not exist. In a case report on an ultra-marathoner competing in a six-day ultra-marathon, the athlete consumed 34.6% fat in his daily food intake (21). Nonetheless, body fat decreased in the first two days and was unchanged until the end of the race. In addition, performance slowed down after the first two days. Ultra-endurance athletes consume approximately 19% of energy as fat, which is higher than consumed energy in the form of protein (Table 5).
Intake of protein
Regarding protein intake, athletes consume approximately 12% of ingested energy as protein during racing. An observational field study at the 'Race across America' showed that ultra-endurance cyclists ingest rather large amounts of protein (121). One might assume that athletes experienced a loss in skeletal muscle mass and tried to prevent this loss by using amino acids. A recent study tried to investigate whether an increase in amino acids during an ultra-marathon prevents skeletal muscle damage (130). The intake of amino acids showed no effect on parameters related to skeletal muscle damage.
Intake of ergogenic supplements, vitamins and minerals
A dietary supplement, such as vitamins and minerals, is characterized as a product which can be used to address physiological or nutritional issues in sports. It may provide a convenient or practical means of consuming special nutrient requirements for sport activity, or it may be used to prevent/re-verse nutritional deficiencies that commonly occur in athletes. The basis of the dietary supplement is an understanding of nutritional requirements and physiological effects of exercise. When the supplement is used to meet a physiological/nutritional goal triggered by sport activity, it may be proven to enhance sports performance (131). Vitamin and mineral supplements are frequently used by competitive and recreational ultra-endurance athletes during training (122), (123), (126), (127) and competitions (120-123).
The intake of ergogenic supplements, vitamins and minerals in ultra-endurance athletes and its effect on performance has been investigated in a number of studies (125), (126), (128). In long-distance triathletes, over 60% of the athletes reported using vitamin supplements, of which vitamin C (97.5%), vitamin E (78.3%), and multivitamins (52.2%) were the most commonly used supplements during training. Almost half (47.8%) the athletes who used supplements did so to prevent or reduce cold symptoms (128). The regular intake of vitamins and minerals seems, how-ever, not to enhance ultra-endurance performance (125), (126). In the 'Deutschlandlauf 2006' of over 1,200 km in 17 consecutive stages, athletes with a regular intake of vitamin and mineral supplements during the four weeks before the race finished the competition no faster than athletes without vitamins and minerals . In a Triple Iron ultra-triathlon, athletes with a regular intake of vitamin and mineral supplements prior to the race were not faster (126). Caffeine can be used as an ergogenic aid to help competitors stay awake during prolonged periods, enhance glycogen resynthesis and endurance per-formance (8).
Fluid intake during endurance performance
Ad libitum fluid intake seemed to be the best strategy to prevent EAH and to maintain plasma sodium concentration (52), (83), (94), (132-135). Low fluid intake between 300 ml/h and 400 ml/h seemed to prevent EAH (52), (106), (132). In a 4 h march a mean ad libitum fluid intake of approximately 400 ml/h maintained serum sodium concentration (132). A fluid consumption of approximately 400 ml/h prevented from EAH in a 161-km race in the cold (103).
Sodium supplementation during endurance performance
One might argue that a supplement of sodium during an endurance race might prevent EAH. How-ever, two studies on Ironman triathletes showed that ad libitum sodium supplementation was indeed not necessary to preserve serum sodium concentrations in athletes competing for about 12 hours in an Iron-man (136), (137).
Conclusions and implications for future research
Regarding these findings ultra-endurance athletes face a decrease in body mass most probably due to a decrease in both fat mass and skeletal muscle mass. During a race, athletes are not able to compensate for their energy deficit. Athletes tend to increase their fluid intake with increasing length of an ultra-endurance performance, which seems to result in both an increased risk of EAH and limb swelling. In summary, an energy deficit seems to be unavoidable in ultra-endurance performances. The best strategy to prevent both EAH and limb swelling is to minimize fluid intake to approximately 300-400 ml per hour.
Declaration of interest
The authors report no conflicts of interest.
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Accepted: November 28, 2013
Published: December 20, 2013
Address for correspondence: PD Dr. med. Beat Knechtle
Facharzt FMH fur Allgemeinmedizin Gesundheitszentrum St. Gallen Vadianstrasse 26
9001 St. Gallen Switzerland
Telephone: +41 (0) 71 226 82 82
Fax: +41 (0) 71 226 82 72
Med Sport 17 (4): 200-210, 2013
Copyright [c] 2013 Medicina Sportiva
Gesundheitszentrum St. Gallen, St. Gallen, Switzerland
Institute of General Practice and for Health Services Research, University of Zurich, Zurich, Switzerland
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