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Food Intake and Electrolyte Status of Ultramarathoners Competing in Extreme Heat

  • Nicholas Institute of Sports Medicine and Athletic Trauma Lenox Hill Hospital

Abstract and Figures

To relate changes in laboratory indices to dietary intake during extremely prolonged running and to determine if dietary intake influences the ability of runners to finish an 160 km trail race. We monitored intake and serum chemistries of 26 runners competing in an 160 km foot race in temperatures which peaked at 38 degrees C. Blood was drawn pre-, mid- and post-race. Dietary intake and incidence of gastrointestinal distress or changes in mental status were determined by interview with runners approximately every 13 km. Twenty-three runners completed at least 88 kms and, of these 23 runners, 13 finished 160 km in a mean time of 26.2 +/- 3.6 hours. Finishers ingested nearly 30,000 J, 19.4 +/- 8.1 L of fluid and 16.4 +/- 9.5 g of sodium (Na). Sodium and fluid intake per hour was estimated to be 0.6 g/hour and 0.7 L/hour, respectively. Electrolyte intake during the first half of the race was similar between those that finished the race and those that did not. Finishers ingested fluid at a greater rate than non-finishers (p = 0.01) and tended to meet their caloric needs more closely than did non-finishers (p = 0.09). Body weight was unchanged over time (ANOVA, p = 0.52). Serum Na concentration tended to fall from 143 to 140 mEq/L during the race (p = 0.06), and was inversely correlated with weight loss (p = 0.009). Serum Na concentration was lower mid-race in runners experiencing changes in mental status than in runners without changes (p = 0.04). Fluid intake was inversely correlated with serum Na concentrations (p = 0.04). Most of the runners experienced nausea or vomiting; these symptoms were not related to serum sodium concentration. Hyponatremia (<135 mEq/L) was seen in one runner at 88 kms, but resolved by 160 km. Urinary sodium excretion decreased (p = 0.002) as serum aldosterone concentration increased pre- to post-race (p < 0.001). From start to finish of the race plasma volume increased by 12%. Food and fluid was ingested at a greater rate than described previously. Runners consumed adequate fluid to maintain body weight although dietary sodium fell far short of the recommended 1 g/hour. The rate of fluid intake was greater in finishers than in non-finishers, and finishers tended to more nearly meet their energy needs. Maintenance of body mass despite large exercise energy expenditures in extreme heat is consistent with fluid overload during a running event lasting more than 24 hours in hot and humid conditions.
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Original Research
Food Intake and Electrolyte Status of Ultramarathoners
Competing in Extreme Heat
Beth W. Glace, MS, Christine A. Murphy, PAC, and Malachy P. McHugh, PhD
Nicholas Institute of Sports Medicine and Athletic Trauma (B.W.G., M.P.M.), Lenox Hill Hospital (C.A.M.), New York, New York
Key words: ultramarathon, gastrointestinal distress, hyponatremia, fluid, endurance
Objective: To relate changes in laboratory indices to dietary intake during extremely prolonged running and
to determine if dietary intake influences the ability of runners to finish an 160 km trail race.
Methods: We monitored intake and serum chemistries of 26 runners competing in an 160 km foot race in
temperatures which peaked at 38°C. Blood was drawn pre-, mid- and post-race. Dietary intake and incidence of
gastrointestinal distress or changes in mental status were determined by interview with runners approximately
every 13 km. Twenty-three runners completed at least 88 kms and, of these 23 runners, 13 finished 160 km in
a mean time of 26.2 3.6 hours.
Results: Finishers ingested nearly 30,000 J, 19.4 8.1 L of fluid and 16.4 9.5 g of sodium (Na). Sodium
and fluid intake per hour was estimated to be 0.6 g/hour and 0.7 L/hour, respectively. Electrolyte intake during
the first half of the race was similar between those that finished the race and those that did not. Finishers ingested
fluid at a greater rate than non-finishers (p0.01) and tended to meet their caloric needs more closely than did
non-finishers (p0.09). Body weight was unchanged over time (ANOVA, p0.52). Serum Na concentration
tended to fall from 143 to 140 mEq/L during the race (p0.06), and was inversely correlated with weight loss
(p0.009). Serum Na concentration was lower mid-race in runners experiencing changes in mental status than
in runners without changes (p0.04). Fluid intake was inversely correlated with serum Na concentrations (p
0.04). Most of the runners experienced nausea or vomiting; these symptoms were not related to serum sodium
concentration. Hyponatremia (135 mEq/L) was seen in one runner at 88 kms, but resolved by 160 km. Urinary
sodium excretion decreased (p0.002) as serum aldosterone concentration increased pre- to post-race (p
0.001). From start to finish of the race plasma volume increased by 12%.
Conclusions: Food and fluid was ingested at a greater rate than described previously. Runners consumed
adequate fluid to maintain body weight although dietary sodium fell far short of the recommended 1 g/hour. The
rate of fluid intake was greater in finishers than in non-finishers, and finishers tended to more nearly meet their
energy needs. Maintenance of body mass despite large exercise energy expenditures in extreme heat is consistent
with fluid overload during a running event lasting more than 24 hours in hot and humid conditions.
Little work has been done which prospectively and carefully
examines both food and fluid intake and serum chemistries in
ultra-endurance events. The choice of food and beverage be-
comes a crucial factor in performance during such events.
Carbohydrate intake during prolonged exercise has been shown
to improve time to exhaustion by providing exogenous energy
[1], while sufficient fluid intake is necessary to prevent dehy-
dration [2]. In addition, hyponatremia is well-documented during
prolonged exercise [3,4]. Hyponatremic runners seeking medical
assistance present with a variety of symptoms that range from
nausea, weakness, confusion, incoordination to grand mal seizures
and coma [5]. We have previously found that runners exercising
nearly continuously for 24 hours experienced nausea and changes
in mental status [6]. Sodium intake for these runners was much
less than recommended (0.5 g/hour vs. 1–2 g/hour) [7] while fluid
and total energy intake were greater than expected. Several run-
ners had also reported profound post-exercise diuresis. These
symptoms were suggestive of hyponatremia although we had not
assessed serum electrolytes.
The purpose of this study was to document changes in blood
Address reprint requests to: Beth W. Glace, M.S., Nicholas Inst. Sports Medicine and Athletic Trauma, Lenox Hill Hospital, 130 East 77th Street, New York, NY 10021.
Presented in part at the American College of Sports Medicine, Indianapolis, IN, June 2000.
Journal of the American College of Nutrition, Vol. 21, No. 6, 553–559 (2002)
Published by the American College of Nutrition
and urine electrolytes and to relate those changes to dietary
intake in runners engaged in a 160 km trail race. We further
sought to determine whether intake had an effect upon the
ability to complete the race and upon gastrointestinal function
or mental status.
Twenty-six volunteers with a mean age of 48.8 8.8 years
(SD) were recruited by letter three months prior to the event. To
be eligible, subjects had to have an anticipated finish time of
less than 24 hours by self-report. According to race results from
the previous two years, this gave us a pool of approximately 85
runners to recruit from and limited us to the top 50% of
competitors according to finish times. The 21 men and 5
women who agreed to participate were mailed questionnaires
regarding their medical and running/training history. The re-
search protocol was approved by the Research and Clinical
Investigations Committee of Lenox Hill Hospital, and written
informed consent was obtained prior to subject participation.
Participants were paid $100 at study completion.
On the evening prior to the race, before the pre-race meal,
participants provided a urine sample that was placed on ice.
After reviewing the medical history, body mass was determined
in shorts (jog bra for women), with shoes, on a calibrated scale
and body fat was determined with Skindex skinfold calipers
(Caldwell, Justiss & Co., Fayetville, AR) that use a gender- and
age-adjusted formula [8,9]. Blood was drawn from an antecu-
bital vein within two minutes of being seated. An aliquot of
whole blood was analyzed within three hours for hemoglobin
(HemoCue, Lee Diagnostics AB, Medical) and hematocrit. The
remaining sample was centrifuged and separated. The serum
was frozen and later analyzed for aldosterone, sodium, potas-
sium, osmolality and glucose. Plasma volume changes were
calculated according to the methods described by Strauss et al.
using hemoglobin and hematocrit [10]. Runners were provided
with dietary intake records and instructed to record their food
intake for the 12 hours preceding the race, including the pre-
race meal. In addition, they were asked to record the type and
amount of non-steroidal anti-inflammatory drugs (NSAIDs)
The runners were met just prior to the 4:30 a.m. race start,
where the pre-race food records were collected and reviewed.
Temperatures on race day ranged from 21°–38°C. The race
course consisted primarily of dirt roads and trails with 4500
meters of ascents and descents. There were 37 official food
stations spaced throughout the course. Investigators manned 12
food stations, at approximately 13 km intervals. A checklist of
supplied food items was used to record the type and quantity of
food, beverages and NSAIDs taken by the runners at each of
the observed stations. Since runners could eat from food sta-
tions other than the ones monitored by investigators and could
eat foods supplied by support crews, they were also asked to
recall everything they had ingested since we last interviewed
them. Runners were asked to keep any wrappers from foods
eaten on the trail until they next saw us, to help account for
their intake. At each interview the runners were asked if they
had experienced any gastrointestinal symptoms (GiSx) i.e. nau-
sea, vomiting, diarrhea, and were observed for changes in
mental status (MSx) such as confusion, disorientation, or in-
ability to concentrate.
Blood samples were collected again at 88 km and at the
finish line and analyzed or frozen, as described above. Urine
collected pre- and post-race was frozen and later analyzed for
electrolytes and osmolality. Body mass was assessed pre-race,
at 70 km, 110 km, 133 km and immediately after the finish,
after voiding and prior to taking any further food or fluid.
Skinfold measurements were repeated after towel drying. En-
ergy expenditure during the event was estimated using a step-
wise calculation using body mass, mean velocity and time spent
running [11].
Dietary Analysis
The NutriBase Nutrition Management Software, Clinical
Version, (CyberSoft, Inc. Phoenix, AZ) was used to calculate
the nutritional composition of the foods and fluids consumed.
Runners were subsequently interviewed by phone if clarifica-
tion was required, e.g. to obtain brand names of specialized
sportsupplements. The manufacturers were contacted to
provide nutritional composition of these products, and the data
was added to the nutritional software database. Where possible,
food items were obtained, and the food was weighed in our
laboratory according to typical serving size. For example, we
standardized handfulsof a variety of food items by having
several staff members repeatedly take a handful of the specified
food. The food was then weighed, and the mean weight was
used as a typical handful. Diets were analyzed for total
calories, macro- and micro-nutrients as well as for total mois-
ture content.
Statistical Analysis
Anthropometric measurements, dietary intake and blood
and urine analysis were examined. A one-way, repeated mea-
sure ANOVA was used to examine changes over the duration
of the race. Two-way mixed model ANOVAs were used to
examine changes overtime between runners: (1) with/without
MSx; (2) finishers and non-finishers. Because non-steroidal
anti-inflammatory drugs (NSAIDs) are associated with GI dis-
tress, ANCOVA with NSAID intake as a confounding variable
was used to compare dietary intake between GISx and No GISx
groups. Statistical significance was established for an alpha
level of 0.05. Bonferroni corrections were used for all post-hoc
Food and Fluid Intake during an Ultramarathon
554 VOL. 21, NO. 6
pair-wise comparisons. All results are reported as means with
standard deviations.
Thirteen of the 26 subjects completed the 160 km course, in
a mean time of 26.2 0.4 hours. Of the non-finishers, all
subjects completed a minimum of 45 km. Eleven of the 13
non-finishers had body mass determined at 70 km. However,
most of the non-finishers dropped out of the race while on the
trail; final body mass determination and blood sampling could
not always be performed at the time the runner dropped out,
unless they happened to stop at a monitored aid station. The
mean change in weight from race start till the last time
weighted during the race, or until the finish, was 0.97 1.8
kg. Finishers and non-finishers did not differ in the magnitude
of weight change, 0.5 1.5 kg vs. 1.2 1.8 kg (p0.27),
respectively. Surprisingly, there was no significant change in
body mass over time in the finishers (p0.52). Finishers
decreased mass by 0.5 kg, representing a 0.6% decline from
pre-race values. Although finishers tended to weigh less pre-
race than non-finishers (66.5 kg vs. 73.8 kg, p0.09), the
mean percent body fat did not differ between groups (12.8
6.1% vs. 15.5 5.9%, p0.22, respectively). There was no
significant change in body fat from pre- to post-race (12.8
6.1% vs. 11.9 3.7%, p0.29).
Dietary Intake
An analysis of dietary records collected for the 12 hours
pre-race revealed that 8986 joules were ingested, of which
carbohydrate intake accounted for 59% (Table 1). Three liters
(1.4) of fluid and 3.2 g (1.9) of sodium were consumed
pre-race. Intake is expressed absolutely and per km/kg, in order
to include runners that did not complete the entire course.
Runners who completed 160 km ingested sodium, protein and
fluid at a greater rate than did non-finishers. Carbohydrates
provided 81% of the 29493 J ingested by those completing the
race. Finishers drank a mean of 19.4 5.6 L, with a range of
11.9 to 28.1 L. Sodium intake was 16.4 6.8 g, with a range
of 4.9 to 27.5 grams. These were consumed at rates of 0.7
L/hour and 0.6 g/hour, respectively. Notably, 16% of the total
fluid intake was contributed by the moisture contained in solid
foods. The greatest rates of fluid and carbohydrate intake
occurred during the 2nd and 3rd quarters of the race (Fig. 1).
The rate of fluid intake was greater for those runners who went
on to complete the entire course, as compared to those who did
not finish, when adjusted for body weight (1.8 0.49 vs. 1.3
0.4 mL/kg/km, p0.011).
The rates of energy expenditure and intake were calculated
for both finishers and non-finishers. Expenditure was substan-
tially greater than energy intake, 40,061 vs. 21,569 J respec-
tively, resulting in a mean deficit of 161 J per km completed.
The energy deficit per km was greater for non-finishers than for
non-finishers (190.6 vs. 132.1 J/km, p0.01).
Blood and Urine Analysis
Twelve of the 13 finishers and nine of the 13 non-finishers
had blood drawn mid-race. Glucose concentration were
90(5.0), 97(5.4), and 95 mg/dL (5.3 mmol/L) pre-, mid- and
post-race, i.e. there was no evidence of hypoglycemia. Serum
potassium concentration was 4.15 mEq/L, 5.85 and 4.18 mEq/L
pre-race, mid-race and post-race, respectively (effect of time
p0.001). Serum sodium concentrations tended to fall from
143.9 mEq/L pre-race, to 140.8 mEq/L mid-race, and to 140.2
mEq/L post-race (p0.06). Hyponatremia, as defined by a
serum Na concentration of less than 135 mEq/L, was observed
in only one runner, at 90 km. The runner complained of both
vomiting, which began at 12 km, and confusion, beginning at
88 km. The runners serum Na concentrations were as follows
pre-, mid-, and post-race: 144 mmol/L, 133 mmol/L and 136
mmol/L, respectively. Changes in body mass inversely paral-
leled the changes in serum Na; his mass was 71.2 kg pre-, 73.9
kg mid-, and 73.0 kg post-race. His mean Na and fluid intakes
were 17.1 g and 24.2 L, respectively. Anecdotally, the runner
reported that he had not urinated prior to his episode of con-
fusion, but that after drinking a beer during the race he began
voiding and felt much better.
Table 1. Nutrient Intake
Joules Fluid (L) Carb (g) Fat (g) Protein (g) Fiber (g) Na (g) K (g)
Pre-Race (n 26) 8986 3359 3.2 1.4 318 144 70 39 67 66 31.7 8.7 3.2 1.9 1.9 1.0
Race All (n 26) 21589 12803 14.1 6.5 1084 609 95 73 84 62 23 16 11.4 7.4 5.1 3.3
Race Finishers
(n 13) 29493 3481 19.4 5.6 1419 622 137 75 128 56 32 15 16.4 6.8 7.2 3.1
Rate of Intake (mL) (g) (mg) (mg) (mg) (mg) (mg)
All /kg/km (n 26) 2.15 1.07 1.57 0.5 0.13 0.07 0.01 0.007 0.009 0.006 0.003 0.002 1.3 0.7 0.06 0.03
Non-Finishers /kg/km
(n 13) 2.15 0.99 1.33* 0.41 0.12 0.07 0.008 0.007 0.006* 0.004 0.002 0.002 0.94* 0.58 0.06 0.04
Finishers Per /kg/km
(n 13) 2.15 1.18 1.8* 0.49 0.14 0.07 0.01 0.007 0.01* 0.006 0.003 0.001 1.60* 0.69 0.06 0.03
* Finishers and non-finishers, p0.01. Values are SD.
Food and Fluid Intake during an Ultramarathon
There was no relationship between total sodium intake and
post-race serum (r 0.07, p0.83) or urinary sodium (r
0.41, p0.17). Post-race serum sodium was affected, how-
ever, by fluid intake during the second half of the race (r
0.58, p0.04) (Fig. 2a); high fluid intakes were correlated
with lower post race serum sodium. Post-race urinary sodium
also tended to be inversely correlated with 2nd half fluid
intakes (r ⫽⫺0.53, p0.06), (Fig. 2b). No relationship was
seen between dietary potassium intake and serum or urinary
potassium levels.
Loss of body weight was inversely correlated with changes
in serum sodium (r 0.58, p0.009). There was no change
in serum osmolality from pre- to post-race (290 11 vs. 283
12 mOsm/kg H
O, p0.15). Serum aldosterone increased
significantly during the race, from 8.3 4.9 to 49.2 3.1 (p
0.001), and mean sodium excretion fell from 74.1 mEq/L
pre-race to 19.4 mEq/L post-race (p0.002). A significant
difference in plasma volume changes was observed between
finishers and non-finishers mid-race. By 90 km non-finishers
experienced a 5% decrease in plasma volume while those who
went on to complete the course had expanded plasma volume
by 3% (Fig. 3). Overall, finishers increased plasma volume by
11.8% from pre- to post-race.
Gastrointestinal symptoms were experienced by 17 of the
26 participants. Upper Gi symptoms were far more prevalent
than lower, with 15/26 describing nausea or vomiting but only
3/26 runners describing diarrhea or intestinal cramping. Run-
ners with GiSx had greater energy intake, and specifically
greater carbohydrate intake, than did runners not experiencing
symptoms (Table 2). The rate of intake of other nutrients was
similar between GiSx and No GiSx groups. Most runners used
NSAIDs (18/26); however, their use was not associated with
GiSx (p0.50). There were no differences in body mass
changes or in serum sodium changes over time between those
who did and those who did not use NSAIDs. Runners without
GiSx had completed longer runs during training or racing than
had runners with symptoms, 112 vs. 68 km (p0.02).
Nine of 26 runners complained of MSx, which ranged in
severity from mild confusion to hallucinations. Dietary intakes
were not different between runners with and without MSx. Of
the finishers, mid-race serum Na was lower in those reporting
MSx (137.5 mg/dL) compared to those with no MSx (141.9
Fig. 1. Intake per quarter. Fluid: effect of time, p0.04; Carbohydrate:
effect of time, p0.004. Values are SD.
Fig. 2. Relationship of fluid intake to post-race serum and urinary
sodium concentrations.
Fig. 3. Percent change in plasma volume from pre-race to mid-race for
finishers and non-finishers *p0.047, and from pre- to post-race.
Values are SD.
Food and Fluid Intake during an Ultramarathon
556 VOL. 21, NO. 6
mg/dL, p0.04). The rate of serum sodium change did not
differ between MSx (0.037 mg/dL/km) and no MSx (0.038
mg/dL/km). The rate of dietary potassium intake was lower in
seven runners who complained of muscle cramping (27.2 mg/
km) compared to those without cramping (46.8 mg/km, p
0.046). There was no association between cramping and so-
dium or fluid intake prior to, or during, the race.
While other studies have examined dietary intake during
prolonged exercise, many have used small sample populations
[12,13], were limited by using diet recall methods immediately
following the race [12] or used dietary data collected during
subsequent telephone surveys [14]. While conveniently ap-
plied, these methods are associated with inaccuracies in dietary
data and might be expected to be even less reliable after
physically exhausting exercise. Furthermore, the ultra-endur-
ance events described were of far shorter duration than the
event being reported upon here [13,14]. This study is unique in
that we repeatedly interviewed athletes regarding, and ob-
served, food intake throughout more than 24 hours of contin-
uous exercise.
Our sample population was fairly representative of the field
of entrants: the mean finish times were 26.2 vs. 25.1 hours,
respectively. In previous years the finish rate for this race has
been approximately 75%; in 1999 the rate of completion was
only 44% for the overall field of entrants and 50% for those
runners for whom we collected data. The attrition rate was
likely due to the extreme environmental conditions of high
humidity and temperature.
Our most important finding was that body mass was very
well-maintained throughout the race, despite extreme energy
expenditure and thermal stress. A 3% to 4% decrease in body
mass during ultra-marathons has been reported previously [15].
It has been suggested that failure to lose approximately 2 kg
might actually represent fluid overload since the utilization of
fat and glycogen stores should result in net loss of mass. The
estimated energy deficit during this race ought to have resulted
in a loss of approximately 0.64 kg of body mass, if all of the
unmet energy needs came at the expense of body fat [17]. The
estimated expense of body fat would account for all of the
measured change in body mass and would suggest that runners
experienced a slight relative gain in body fluids. Recommen-
dations for fluid consumption during ultra-marathons have var-
ied from 0.5 to 1 L/hour [18] to 0.6 to 2.4 L/hour [2]. Our data
demonstrates that an intake of 0.74 liters of moisture per hour
was more than sufficient to maintain body weight during such
prolonged but low-intensity exercise and supports recommen-
dations of fluid consumption of no more than 1 L/hour in
Fluid overload has been suggested to be the primary factor
contributing to low serum sodium levels [19]. It has been
estimated that ultra-distance athletes would need to lose about
4% of their body weight in order to maintain serum sodium [19,
20]. We observed a strong indirect relationship between weight
change and serum sodium. Weight maintenance may represent
an inappropriate retention of fluid in the vascular space, as
suggested by the expansion of blood volume. Despite the cooler
night temperatures and decreased pace during the latter stages
of the race, fluid intake was similar between the first and
second halves of the event. It is feasible that 19 liters of fluid
ingested in one day exceeded sweat rate and the kidneys
capacity to excrete excess fluid in some individuals.
Goldberger has recommended that athletes engaged in very
prolonged exercise ingest 1 g/hour of sodium [7]. The athletes
we observed ate approximately half that amount. Serum sodium
concentrations overall tended to fall throughout the race, and
plasma volume was expanded under environmental conditions
which would be expected to result in a contraction of plasma
volume and in hemoconcentration [21]. While serum sodium
would typically be expected to drive plasma expansion, Gast-
mann et al. have suggested that plasma expansion during 24
hours of exercise may result from a carbohydrate-induced os-
motic gradient [22]. Serum Na concentrations declined inde-
pendently of serum osmolality; the high rate of carbohydrate
intake may have contributed to serum osmolality and to the
retention of fluid in the vascular space [19, 23, 24]. In a
previous study at the same race we found that runners ingested
nearly identical amounts of moisture and sodium while com-
peting under far more mild conditions. We suspect that had
conditions been less severe plasma volume may have ex-
panded, and serum Na concentration declined, to an even
greater degree.
Another important finding of this study is that runners
seemed willing and able to ingest far more food than has been
described. We believe that the extreme duration of exercise,
Table 2. Nutrient Intake and Gastrointestinal Distress
(J/kg/km) CHO
(g/kg/km) Fat (g/kg/km) Protein
(g/kg/km) Fluid
(mg kg
GI 0.61 0.06# 0.15 0.02* 0.01 0.002 0.009 0.002 1.6 0.1 1.4 0.2
No GI 0.33 0.08# 0.09 0.02* 0.01 0.002 0.009 0.002 1.5 0.1 1.1 0.2
# Groups significantly different, p0.005.
* Groups significantly different, p0.02. Values are SD.
Food and Fluid Intake during an Ultramarathon
and therefore the reduced intensity of exercise, greatly influ-
enced the amount and type of foods ingested. Running pace
averaged 6.5 km/hour overall and only 5.7 km/hour in the
second half, as compared to that of participants in a 100 km run
who averaged nearly 10 km/hour [13]. While runners engaged
in higher intensity exercise often rely heavily upon the carbo-
hydrate contained in liquids or fruits to provide energy [25],
runners in this study ate substantial quantities of solid food,
including items such as fried chicken and peanut butter sand-
wiches, obtaining 17% of total energy from fats. Finishers
consumed approximately 30,000 Joules, with a range of 11,832
to 47,359 Joules, at a mean rate of 176 J/km. This is similar to
the data collected during a previous 160 km race [6], during the
Alaskan Iditasport [12] and the Tour de France [26]. However,
the observed rate we observed was fourfold greater than de-
scribed by others during running races [13].
Dietary intake may have affected the ability of runners to
finish the race. The deficit between estimated energy expended
and energy consumed tended to be larger in non-finishers
compared to finishers: finishers tended to more nearly meet
their energy needs. Rehrer et al. estimated fluid intake to be
56.8 mL/km during a 67 km race, or half the rate we observed
[14]. Our volunteers consumed a large amount of solid food
which contributed a significant amount of moisture and may, in
part, explain the high fluid intakes.
The incidence of mental status changes was quite high
during the race. We found that mental status changes were
associated with lower serum Na concentration and that serum
Na concentrations were associated with high fluid intakes.
Serum sodium concentration was lower mid-race in those ath-
letes experiencing MSx, but there was no difference in dietary
intake of sodium between those that did and did not report
MSx. While high fluid intake increased the likelihood of com-
plaints of mental status change, finishers did ingest fluid at a
greater rate than those who dropped out of the race. The mental
status changes, then, were not typically severe enough to result
in withdrawal from the competition. In a previous study of
ultra-marathoners competing on the identical course in less
severe conditions we similarly found that those with mental
status changes ingested more fluid than those without symp-
toms, but that overall finish time was not affected by the
occurrence of mental status change [6].
Although dehydration has been postulated to contribute to
GI distress [14], we found no relationship between markers of
dehydration (i.e. weight loss, osmolality) and GI symptoms.
The lack of a relationship could be due to the minimal dehy-
dration experienced by runners in this study. Hypertonic car-
bohydrate beverages have been shown to increase risk of GI
problems in triathletes [25]. We did find an increased risk of
developing GI symptoms with increasing caloric intake, spe-
cifically of carbohydrate intake. The rate of carbohydrate intake
was 54 g/hour, plus 5 g/hour of fat and protein, an intake which
exceeds the limit suggested by Kreider et al. during ultra-
distance running, of 1550 g/hour [2]. As with the mental status
change, however, most of the GI symptoms were not severe
enough to warrant withdrawal from the race.
Rehrer et al. and Keefe et al. reported that lower GI symp-
toms were far more prevalent than upper GI symptoms in
shorter ultra-marathon events [14,27]. However, we found a
much greater incidence of moderate to severe upper GI distress,
i.e. nausea or vomiting, than of lower GI symptoms. The high
incidence of upper GiSx may be a function of race duration [6].
Better trained runners were less likely to experience GI distress.
A protective effect of training on the incidence of GI symptoms
has been reported previously [6,28]. Brocke et al. found that
ultra-distance athletes often experience endotoxemia during
very prolonged exercise with symptoms of nausea and vomit-
ing, secondary to increased intestinal permeability [29]. Inter-
estingly, better trained runners were found to have better im-
munity to endotoxins and fewer symptoms. The authors
speculated that training may confer a protective effect by
increasing antibodies to endotoxins.
We studied food and moisture intake, markers of serum
electrolyte status and disturbances in gastrointestinal and men-
tal status in runners engaged in 21 to 30 hours of near contin-
uous exercise. The slow pace in this long duration race may
have resulted in low sweat rates, while simultaneously allowing
for greater food and fluid consumption than previously re-
ported. Runners ate more than has been previously described in
running races and ingested sufficient fluid to maintain body
weight. Although high fluid intakes were associated with de-
creased serum sodium and increased risk of mental status
change, finishers ingested fluid at a greater rate than those who
did not complete the race and more closely met their energy
requirements. Collectively, we observed a minimum of weight
loss, a high incidence of upper gastrointestinal distress with
high carbohydrate intake and an expansion in plasma volume
despite extreme environmental conditions and exercise stress.
The authors wish to thank Maria Pagano for her enthusiastic
assistance despite severe sleep deprivation, and Dr. Maria
Devita for lending her expertise in renal handling of fluids and
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Food and Fluid Intake during an Ultramarathon
... Similarly, Glace et al. reported an inverse correlation between changes in body weight and serum sodium concentration in a prospective observational study involving 26 carefully selected trained ultra-marathon runners [75]. Only one case of a temporary drop in sodium level below 135 mmol/L was documented. ...
... Only one case of a temporary drop in sodium level below 135 mmol/L was documented. Urinary sodium excretion decreased during the race, while plasma volume increased by 12% toward the end [75]. The characteristics of the studies from Noakes et al. [47] and Glace et al. [75] are shown in Table 3. Table 3. Hydration characteristics of participants in the studies from Noakes et al. [47] and Glace et al. [75]. ...
... Urinary sodium excretion decreased during the race, while plasma volume increased by 12% toward the end [75]. The characteristics of the studies from Noakes et al. [47] and Glace et al. [75] are shown in Table 3. Table 3. Hydration characteristics of participants in the studies from Noakes et al. [47] and Glace et al. [75]. The observational study by Reid et al. examined haematological and biochemical parameters during a marathon, incidence rates, and the change in parameters with the use of analgesics in 134 athletes [76]. ...
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Exercise-associated hyponatremia (EAH) was first described as water intoxication by Noakes et al. in 1985 and has become an important topic linked to several pathological conditions. However, despite progressive research, neurological disorders and even deaths due to hyponatremic encephalopathy continue to occur. Therefore, and due to the growing popularity of exercise-associated hyponatremia, this topic is of great importance for marathon runners and all professionals involved in runners’ training (e.g., coaches, medical staff, nutritionists, and trainers). The present narrative review sought to evaluate the prevalence of EAH among marathon runners and to identify associated etiological and risk factors. Furthermore, the aim was to derive preventive and therapeutic action plans for marathon runners based on current evidence. The search was conducted on PubMed, Scopus and Google Scholar using a predefined search algorithm by aggregating multiple terms (marathon run; exercise; sport; EAH; electrolyte disorder; fluid balance; dehydration; sodium concentration; hyponatremia). By this criterion, 135 articles were considered for the present study. Our results revealed that a complex interaction of different factors could cause EAH, which can be differentiated into event-related (high temperatures) and person-related (female sex) risk factors. There is variation in the reported prevalence of EAH, and two major studies indicated an incidence ranging from 7 to 15% for symptomatic and asymptomatic EAH. Athletes and coaches must be aware of EAH and its related problems and take appropriate measures for both training and competition. Coaches need to educate their athletes about the early symptoms of EAH to intervene at the earliest possible stage. In addition, individual hydration strategies need to be developed for the daily training routine, ideally in regard to sweat rate and salt losses via sweat. Future studies need to investigate the correlation between the risk factors of EAH and specific subgroups of marathon runners.
... Studies investigating CHO intake of ultra-runners during competition have shown large variations in intake (25-71 g·h. −1 ), at elite and non-elite levels (Glace et al., 2002;Moran et al., 2011;Stuempfle et al., 2011;Costa et al., 2014;Wardenaar et al., 2015;Stellingwerff, 2016;Martinez et al., 2018;Lavoué et al., 2020). Faster/elite runners have been shown to consume more hourly CHO than slower/amateur runners (Stellingwerff, 2016), and finishers reported to consume more than non-finishers (Stuempfle et al., 2011). ...
... In the present study, mean in-race CHO intake was in the 30-60 g·h −1 range for the runners, but fell short of guidance for up to 90 g·h −1 . Hourly in-race CHO intake was low compared to other studies on prolonged ultra-endurance running (12 h plus) including both amateur finishers (66 g·h −1 ), non-finishers (42 g·h −1 ; Stuempfle et al., 2011), elite-runners (71 g·h −1 ;Stellingwerff, 2016) in 100-mile mountain races, runners in a 100-mile trail race (54 g·h −1 ; Glace et al., 2002), and a 24-h track world championship (62 g·h −1 ; Lavoué et al., 2020). However, Costa et al. (2014) recorded similar CHO consumption rates (37 ± 24 g·h −1 ) to the present study for participants during the same G24 event in 2011/2012. ...
... A sustained intensity of 45 ± 17% VO 2max demonstrates that, in ultra-events, exercise intensity is low to moderate, but when sustained over 24 h this becomes a significant metabolic challenge. Other studies have reported low mean heart rates in ultraendurance running events (Clemente-Suarez, 2015;Stellingwerff, 2016) and low pace (Glace et al., 2002;Clemente-Suarez, 2015;Ramos-Campo et al., 2016). It therefore could be suggested that in-race CHO recommendations for ultra-runners need not be high, given that endogenous fat stores will likely contribute significantly to energy requirements, and total CHO oxidation rates will be lower at lower intensities (Jeukendrup, 2014). ...
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Carbohydrate (CHO) intake recommendations for events lasting longer than 3h indicate that athletes should ingest up to 90g.h. ⁻¹ of multiple transportable carbohydrates (MTC). We examined the dietary intake of amateur (males: n =11, females: n =7) ultra-endurance runners (mean age and mass 41.5±5.1years and 75.8±11.7kg) prior to, and during a 24-h ultra-endurance event. Heart rate and interstitial glucose concentration (indwelling sensor) were also tracked throughout the event. Pre-race diet (each 24 over 48h) was recorded via weighed intake and included the pre-race meal (1–4h pre-race). In-race diet (24h event) was recorded continuously, in-field, by the research team. Analysis revealed that runners did not meet the majority of CHO intake recommendations. CHO intake over 24–48h pre-race was lower than recommended (4.0±1.4g·kg ⁻¹ ; 42±9% of total energy), although pre-race meal CHO intake was within recommended levels (1.5±0.7g·kg ⁻¹ ). In-race CHO intake was only in the 30–60g·h ⁻¹ range (mean intake 33±12g·h ⁻¹ ) with suboptimal amounts of multiple transportable CHO consumed. Exercise intensity was low to moderate (mean 68%HR max 45%VO 2max ) meaning that there would still be an absolute requirement for CHO to perform optimally in this ultra-event. Indeed, strong to moderate positive correlations were observed between distance covered and both CHO and energy intake in each of the three diet periods studied. Independent t -tests showed significantly different distances achieved by runners consuming ≥5 vs. <5g·kg ⁻¹ CHO in pre-race diet [98.5±18.7miles (158.5±30.1km) vs. 78.0±13.5miles (125.5±21.7km), p =0.04] and ≥40 vs. <40g·h ⁻¹ CHO in-race [92.2±13.9miles (148.4±22.4km) vs. 74.7±13.5miles (120.2±21.7km), p =0.02]. Pre-race CHO intake was positively associated with ultra-running experience, but no association was found between ultra-running experience and race distance. No association was observed between mean interstitial glucose and dietary intake, or with race distance. Further research should explore approaches to meeting pre-race dietary CHO intake as well as investigating strategies to boost in-race intake of multiple transportable CHO sources. In 24-h ultra-runners, studies examining the performance enhancing benefits of getting closer to meeting pre-race and in-race carbohydrate recommendations are required.
... Thus, dehydration reduces exercise performance because of reduced blood flow to the muscles or skin during exercise and accelerates hyperthermia because of prolonged exercise. Associated physiologic changes include decreased plasma volume, blood pressure, and cardiac output; decreased blood flow to the kidneys; and impaired regulation of body temperature [6,7]. During exercise, electrolyte and water homeostases are maintained by the water-regulating hormone known as the antidiuretic hormone (ADH) along with the renin-angiotensin-aldosterone system [7]. ...
... Associated physiologic changes include decreased plasma volume, blood pressure, and cardiac output; decreased blood flow to the kidneys; and impaired regulation of body temperature [6,7]. During exercise, electrolyte and water homeostases are maintained by the water-regulating hormone known as the antidiuretic hormone (ADH) along with the renin-angiotensin-aldosterone system [7]. ADH is secreted from the posterior pituitary gland to suppress water loss because of sweating as a result of exposure to high temperature or exercise, whereas aldosterone, secreted from the adrenal cortex, plays a role in preserving Na + in the extracellular fluid and increasing the excretion of K + in urine [8]. ...
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This study aimed to compare the physiologic effects of regular water consumption to those of electrolyte drink consumption in exercise capacity and recovery after exhaustive exercise. The participants were 10 healthy young men who exercised on a treadmill before and after receiving regular water and an electrolyte drink (3RINK) four weeks later. A 250-mL fluid volume was ingested 30 min before exercise and immediately after. Body composition, water metabolizing hormones, and body electrolytes were analyzed at rest (R), immediately after exercise (P0), and 1 h after exercise (P1). Moreover, serum lactic acid levels were measured to determine recovery. Total body water, intracellular, and extracellular water levels were higher after consuming 3RINK at P0 than at R. There was no interaction effect between the types of fluids and antidiuretic hormone, aldosterone, and renin levels. Hematocrit levels showed an interaction effect between the type of fluid and period. Sodium levels were significantly different between the different types of fluids at P0 and P1. Finally, an interaction effect was noted between each type of fluid and serum lactate levels. Thus, 3RINK intake before and after exhaustive exercise increased body capacity to retain water, improved exercise ability, and reduced exercise-related fatigue.
... Consequently, exercise performance may decline due to decreased blood pressure, increased heart rate, and reduced cardiac function (Glace et al., 2002). Adequate hydration during training or competition prevents dehydration, maintains optimal body temperature, and improves performance. ...
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Objective : To verify the hydration effects of ORS on athletes by comparing the degrees of fluid absorption and plasma volume changes following beverage consumption, including ORS. Methods : Thirty-one participants visited the testing laboratory 4 times at 1-week intervals to consume 1 liter of beverage (e.g., water, ORS, and two sports drinks) for 30 minutes on each visit. The urine output was measured 4 times at 1 hour, 2 hours, 3 hours, and 4 hours after beverage consumption. A blood sample was collected 3 times at 1 hour, 2 hours, and 3 hours after beverage consumption. Body weight was measured once in 4 hours after beverage consumption. Results : Body weight change was smaller for ORS than for water, SpD1, and SpD2 (p<0.05). Cumulative urine output in 4 hours was lower for ORS, SpD1, and SpD2 than for water (p<0.05), and it was lower for ORS than for SpD2 (p<0.05). BHI in 4 hours was higher for ORS, SpD1, and SpD2 than for water (p<0.05), and it was higher for ORS than for SpD2 (p<0.05). There was no significant difference in PVC for different beverages at all test times, i.e.., 1 hour, 2 hours, and 3 hours. Conclusion : We evaluated the hydration effects of the consumption of beverages, such as water, sports drink, and ORS in athletes. ORS and sports drinks were more effective than water. A comparison between ORS and sports drinks showed that the result could vary depending on the type of sports drink.
... The etiology and frequency of GIS during ultraendurance races have been extensively described and appear to mainly result from physiological (reduction in splanchnic blood flow) and mechanical factors (pounding and jostling during running) [4,6,26,27], as well as the high intake, during the race (particularly hyperosmolar CHO solutions) [6]. Although there appears to be no difference in intake (fluids, CHO, or energy) between participants who experience GIS and those who do not [4,7,27,28], these elite athletes affirmed that GIS altered their planned nutritional intake. A real-time collection of GIS data showed that all GIS, with the exception of lower GIS (diarrhea), occurred at mid-race (6-15 h), coinciding with the nocturnal and colder period and therefore concomitantly with the observation of large and growing differences between actual and planned intake. ...
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Background: A food and fluid intake program is essential for ultraendurance athletes to maximize performance and avoid possible gastrointestinal symptoms (GIS). However, the ability to follow such a program during a race has been under-assessed. We thus investigated the fluctuations of food and fluid intake during the 24-h run World Championship of 12 elite athletes (6 men and 6 women; age: 46 ± 7 years, height: 170 ± 9 cm, weight: 61.1 ± 9.6 kg, total distance run: 193-272 km) and assessed their ability to follow their nutritional program. Methods: Real-time overall intake (fluids, energy, and macronutrients) was recorded and compared to that of their program. The temporal difference in absolute values and the degree of divergence from their program were assessed, divided into four 6-h periods. GIS were recorded during the race. A questionnaire identifying the details of their nutritional program and the self-assessed causes of their inability to follow it was completed by the participants the day after the race. Results: Water, total fluid, carbohydrates (CHO), and energy intake decreased during the last quarter of the 24-h ultramarathon relative to the first half (p = 0.024, 0.022, 0.009, and 0.042). However, the differences were no longer significant after these values were normalized by the number of passages in front of the supply tent. The participants progressively failed to follow their nutritional program, with the intake of their planned items dropping to approximately 50% during the last quarter. However, this was adequately compensated by increases in unplanned foods allowing them to match their expected targets. GIS, lack of appeal of the planned items, and attractivity of unplanned items were the main explanations given for their deviation from the program (64, 27, and 27%, respectively). Conclusion: Despite evident difficulty in following their nutritional programs (mostly attributed to GIS), elite ultraendurance runners managed to maintain high rates of fluid and food intake during a 24-h ultramarathon and therefore still met their planned elevated nutritional objectives.Abbreviations: CHO: carbohydrates, GIS: gastrointestinal symptoms.
... The failure of athletes to replace 100% of BW losses from ad libitum FI has been described as "involuntary" or "voluntary" dehydration (35,36). Laboratory and field data, however, suggest that the body primarily defends POsm, and not body water during prolonged endurance exercise (37)(38)(39)(40)(41)(42)(43)(44). Furthermore, complete replacement of fluid loss is accompanied by a reduction in BNa + during prolonged endurance exercise (45)(46)(47)(48), without offering any performance benefit (48,49). ...
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Introduction Hyponatremia often occurs during the practice of endurance sports. We evaluated the impact on hyponatremia of the hydration recommendations of the Third International Exercise-Associated Hyponatremia Consensus Development Conference 2015 (3IE-AHCD) during the 2017 Gran Trail de Peñalara marathon (GTP) and the Vitoria Gasteiz Ironman triathlon (VGI). Methods Prospective study of GTP and VGI athletes participating in four information sessions in the months prior to the events, to explain that hydration should only be according to their level of thirst, per the recommendations of the 3IE-AHCD. Consenting event finishers were included in final analysis. Pre- and post-race anthropometric and biochemical parameters were compared. Results Thirty-six GTP (33 male) and 94 VGI (88 male) finishers were evaluated. GTP race median fluid intake was 800 ml/h, with 900 ml/h in the VGI race. 83.3% GTPfin and 77.6% VGIfin remained eunatremic (blood sodium 135–145 mmol/L). Only 1/36 GTP and 1/94 VGI participant finished in hyponatremia, both with a sodium level of 134 mmol/L. Fourteen percent of GTP, and 21.2% of VGI participants finished in hypernatremia, with no increase in race completion times. No participating athlete required medical attention, except for musculoskeletal complaints. Pro-BNP and Copeptin levels rose significantly. Changes in copeptin levels did not correlate with changes in plasma osmolality, nor total body water content in impedance analysis. Conclusions Recommending that athletes' fluid intake in endurance events be a function of their thirst almost entirely prevented development of hyponatremia, without induction of clinically significant hypernatremia, or a negative repercussion on race completion times.
... Aussi, la capacité de l'athlète à ingérer le plus d'énergie possible durant l'ultramarathon devient l'enjeu primordial de sa performance. En effet, il a été observé que les personnes qui terminent une épreuve de course en sentier de 160 km ont un déficit énergétique moins grand que celles qui n'y parviennent pas (- 3,6 kcal/km vs - 45,6 kcal/km) (9). ...
... Between 30% and 90% of these athletes have experienced some types of GI problem while competing [6,8,20,32,35,36]. While the causes of GI symptoms during prolonged exercise are multifactorial [32,37,38], CHO contained in foods and beverages could intensify these situations [39], and so GI problems could be another reason why SOUT athletes do not adhere to nutritional recommendations [5,6,8,32,35,38,40,41]. However, GI problems caused by CHO intake could be reduced by intestinal training and suitable hydration and nutrition strategy [8,42]. ...
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Due to the high metabolic and physical demands in single-stage one-day ultra-trail (SOUT) races, athletes should be properly prepared in both physical and nutritional aspects in order to delay fatigue and avoid associated difficulties. However, high carbohydrate (CHO) intake would seem to increase gastrointestinal (GI) problems. The main purpose of this systematic review was to evaluate CHO intake during SOUT events as well as its relationship with fatigue (in terms of internal exercise load, exercise-induced muscle damage (EIMD) and post-exercise recovery) and GI problems. A structured search was carried out in accordance with PRISMA guidelines in the following: Web of Science, Cochrane Library and Scopus databases up to 16 March 2021. After conducting the search and applying the inclusion/exclusion criteria, eight articles in total were included in this systematic review, in all of which CHO intake involved gels, energy bars and sports drinks. Two studies associated higher CHO consumption (120 g/h) with an improvement in internal exercise load. Likewise, these studies observed that SOUT runners whose intake was 120 g/h could benefit by limiting the EIMD observed by CK (creatine kinase), LDH (lactate dehydrogenase) and GOT (aspartate aminotransferase), and also improve recovery of high intensity running capacity 24 h after a trail marathon. In six studies, athletes had GI symptoms between 65–82%. In summary, most of the runners did not meet CHO intake standard recommendations for SOUT events (90 g/h), while athletes who consumed more CHO experienced a reduction in internal exercise load, limited EIMD and improvement in post-exercise recovery. Conversely, the GI symptoms were recurrent in SOUT athletes depending on altitude, environmental conditions and running speed. Therefore, a high CHO intake during SOUT events is important to delay fatigue and avoid GI complications, and to ensure high intake, it is necessary to implement intestinal training protocols.
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Ultra-marathon running has developed enormously during the past 15 years. One of the most common experiences ultra-marathon runners share at the end of their effort is a hallucinatory state that appear in form of images, voices, and senses. The aim of the study was to document the hallucinations ultra-marathon runners’ experience during races, the conditions during which ultra-marathon runners experience hallucination, and the runners’ perceptions, feelings, and beliefs towards those phenomena. Nineteen ultra-marathon runners that had previous experiences of hallucinations during an ultra-marathon running race participated in the study. The runners were interviewed in person and answered questions referring the type of races and the point of the races they experienced hallucinations, the nature, content, and duration of hallucinations, the way they felt and cope with the phenomenon while experiencing it, the way significant others and friends perceive those experiences, and the way they personal perceive the hallucinations phenomena. Thematic analysis was used to analyze all data. The interviews revealed that hallucination phenomena exist during ultra-marathon efforts. Runners claimed hallucinations appear under specific circumstances (sleep deprivation, physical & mental exhaustion, nutrition deficiency) and vary in form and duration. Their content presents some common patterns. Runners do not hesitate to discuss their hallucination experience, and they perceive the phenomenon as part of the unique experiences they live during ultra-marathon running. An experience most find challenging and enjoy talking about, while trying to understand and cope with it.
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Digestion is a process which takes place in resting conditions. Exercise is characterised by a shift in blood flow away from the gastrointestinal (GI) tract towards the active muscle and the lungs. Changes in nervous activity, in circulating hormones, peptides and metabolic end products lead to changes in GI motility, blood flow, absorption and secretion. In exhausting endurance events, 30 to 50% of participants may suffer from 1 or more GI symptoms, which have often been interpreted as being a result of maldigestion, malabsorption, changes in small intestinal transit, and improper food and fluid intake. Results of field and laboratory studies show that pre-exercise ingestion of foods rich in dietary fibre, fat and protein, as well as strongly hypertonic drinks, may cause upper GI symptoms such as stomach ache, vomiting and reflux or heartburn. There is no evidence that the ingestion of nonhypertonic drinks during exercise induces GI distress and diarrhoea. In contrast, dehydration because of insufficient fluid replacement has been shown to increase the frequency of GI symptoms. Lower GI symptoms, such as intestinal cramps, diarrhoea — sometimes bloody — and urge to defecate seem to be more related to changes in gut motility and tone, as well as a secretion. These symptoms are to a large extent induced by the degree of decrease in GI blood flow and the secretion of secretory substances such as vasoactive intestinal peptide, secretin and peptide-histidine-methionine. Intensive exercise causes considerable reflux, delays small intestinal transit, reduces absorption and tends to increase colonic transit. The latter may reduce whole gut transit time. The gut is not an athletic organ in the sense that it adapts to increased exercise-induced physiological stress. However, adequate training leads to a less dramatic decrease of GI blood flow at submaximal exercise intensities and is important in the prevention of GI symptoms.
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Objective: To record weight changes, fluid intake and changes in serum sodium concentration in ultradistance triathletes. Design: Descriptive research. Setting: Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). Air temperature at 1200 h was 21°C, (relative humidity 91%). Water temperature was 20.7°C. Participants: 18 triathletes. Interventions: None. Main Outcome Measures: Subjects were weighed and had blood drawn for serum sodium concentration [Na], hemoglobin, and hematocrit, pre-race, post-race, and at 0800 h on the morning following the race (recovery); subjects were also weighed at transitions. Fluid intake during the race was estimated by athlete recall. Results: Median weight change during the race = -2.5 kg (p < 0.0006). Subjects lost weight during recovery (median = -1.0 kg) (p < 0.03). Median hourly fluid intake = 716 ml/h (range 421-970). Fluid intakes were higher on the bike than on the run (median 889 versus 632 ml/h, p = 0.03). Median calculated fluid losses cycling were 808 ml/h and running were 1,021 ml/h. No significant difference existed between pre-race and post-race [Na] (median 140 versus 138 mmol/L) or between post-race and recovery [Na] (median 138 versus 137 mmol/L). Plasma volume increased during the race, median + 10.8% (p = 0.0005). There was an inverse relationship between change in [Na] pre-race to post-race and relative weight change (r = -0.68, p = 0.0029). Five subjects developed hyponatremia ([Na] 128-133 mmol/L). Conclusions: Athletes lose 2.5 kg of weight during an ultra-distance triathlon, most likely from sources other than fluid loss. Fluid intakes during this event are more modest than that recommended for shorter duration exercise. Plasma volume increases during the ultradistance triathlon. Subjects who developed hyponatremia had evidence of fluid overload despite modest fluid intakes.
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1. Skinfold thickness, body circumferences and body density were measured in samples of 308 and ninety-five adult men ranging in age from 18 to 61 years. 2. Using the sample of 308 men, multiple regression equations were calculated to estimate body density using either the quadratic or log form of the sum of skinfolds, in combination with age, waist and forearm circumference. 3. The multiple correlations for the equations exceeded 0.90 with standard errors of approximately ±0.0073 g/ml. 4. The regression equations were cross validated on the second sample of ninety-five men. The correlations between predicted and laboratory-determined body density exceeded 0.90 with standard errors of approximately 0.0077 g/ml. 5. The regression equations were shown to be valid for adult men varying in age and fatness.
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This study examined the relationship between gastrointestinal (GI) symptoms and dietary intake in triathletes. Fifty-five male triathletes (age 31 +/- 6 yrs) were surveyed regarding the most recently completed half Iron Man triathlon. Questions were asked regarding GI symptoms and dietary intake. Fifty-two percent complained of eructation and 48% of flatulence. Other symptoms were abdominal bloating, vomiting urge, vomiting, nausea, stomachache, intestinal cramps, and diarrhea. More symptoms occurred while running than at other times. All individuals who had eaten within 30 min of the start vomited while swimming. Fat and protein intake was greater in those who vomited or had the urge to vomit than in those without these symptoms. Of the former, 93% had consumed a hypertonic beverage. Forty percent of those who drank a hypertonic beverage and only 11% of those who drank an iso- or hypotonic beverage had severe complaints. Four of five individuals with stomachache had consumed a strongly hypertonic beverage. All subjects with intestinal cramps had eaten fiber-rich foods in the prerace meal; only 10% of those without cramps had done so.
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One hundred and seventy-two competitors of the Swiss Alpine Marathon, Davos, Switzerland, 1988, volunteered for this research project. Of these volunteers 170 (158 men, 12 women) finished the race (99%). The race length was 67 km with an altitude difference of 1,900 m between the highest and lowest points. Mean age was 39 (SEM 0.8) years. Average finishing times were 8 h 18 min (men) and 8 h 56 min (women). Loss of body mass averaged 3.4% body mass [mean 3.3 (SEM 0.2)%; 4.0 (SEM 0.4)%; men and women, respectively]. Blood samples from a subgroup of 89 subjects (6 women and 83 men) were taken prior to and immediately after completion of the race. Changes in haemoglobin (9.3 mmol.l-1 pre-race, 9.7 mmol.l-1 post-race) and packed cell volume (0.44 pre, 0.48 post-race) were in line with the moderate level of dehydration displayed by changes in body mass. Mean plasma volume decreased by 8.3%. No significant changes in plasma osmolality, sodium, or chloride were observed but plasma potassium did increase by 5% (4.2 mmol.l-1 pre-race, 4.4 mmol.l-1 post-race). Mean fluid consumption was 3290 (SEM 103) ml. Forty-three percent of all subjects, and 33% of those who gave blood samples, complained of gastro-intestinal (GI) distress during the race. No direct relationship was found between the quantity or quality of beverage consumed and the prevalence of GI symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)
Two ultramarathon runners were hospitalized with hyponatremic encephalopathy after completing 80 and 100 km (50 and 62 miles), respectively, of the 1983 American Medical Joggers Association ultramarathon race in Chicago. The two runners consumed such large quantities of free water during the race that apparent water intoxication developed. Both recovered satisfactorily after treatment with intravenous saline. The hyponatremia was caused primarily by increased intake and retention of dilute fluids and contributed to by excessive sweat sodium loss. A possible explanation for the postrace onset of symptoms might be the sudden absorption of fluid in the gastrointestinal tract after exercise ceased, with subsequent further dilution of the plasma sodium. Hyponatremia, which has not been commonly associated with exercise, should be considered as a possible consequence of ultraendurance events. (JAMA 1986;255:772-774)
The fluid and food intakes of 7 male participants in a 100-km ultramarathon were recorded. The mean exercise time was 10 hr 29 min. Nutrient analysis revealed a mean intrarace energy intake of 4,233 kJ, with 88.6% derived from carbohydrate, 6.7% from fat, and 4.7% from protein. Fluid intake varied widely, 3.3-11.1 L, with a mean of 5.7 L. The mean decrease in plasma volume at 100 km was 7.3%, accompanied by an estimated mean sweat rate of 0.86 Blood glucose concentrations remained normal during the event, and free fatty acids and glycerol were elevated both during and at the conclusion of the event. No significant correlations were found between absolute amounts and rates of ingestion of carbohydrate and/or fluid and race performance.
The physiological effects of endurance exercise have been a primary area of research in exercise science for many years. This research has led not only to a greater understanding of human physiology but also the limits of human performance. This is especially true regarding the effects of endurance exercise on energy metabolism and nutrition. However, as science has attempted to understand the physiological and nutritional demands of endurance exercise lasting 1 to 3 hours, an increasing number of athletes have begun participating in ultraendurance events lasting 4 to 24 hours. Consequently some research groups are now investigating the physiological responses to ultraendurance training and performance. This paper reviews the literature on ultraendurance performance and discusses nutritional factors that may affect bioenergetic, thermoregulatory, endocrinological, and hematological responses to ultraendurance performance.