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Nutrition in ultra-endurance racing-aspects of energy balance, fluid balance and exercise-associated hyponatremia.

Ultra-endurance performances

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 [125]. 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

Email: beat.knechtle@hispeed.ch

Medicina Sportiva

Med Sport 17 (4): 200-210, 2013

DOI: 10.5604/17342260.1081297

Copyright [c] 2013 Medicina Sportiva

Beat Knechtle

Gesundheitszentrum St. Gallen, St. Gallen, Switzerland

Institute of General Practice and for Health Services Research, University of Zurich, Zurich, Switzerland
COPYRIGHT 2013 Medicina Sportiva
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Author:Knechtle, Beat
Publication:Medicina Sportiva
Article Type:Report
Date:Dec 1, 2013
Words:8588
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