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Effects of three different water temperatures on dehydration in competitive swimmers

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Aims.—The purpose of this study was to evaluate the effects of three different water temperatures on physiological responses (dehydration, sweat rate, urine output, rectal temperature and plasma electrolytes) of competitive athletes during a ‘‘simulated’’ race of 5km in an indoor swimming pool. Methods.—Nine male competitive master swimmers swam 5km with the water at temperatures of 23, 27 and 32 !C. Immediately before (Pre) and after (Post) each trial, samples of blood and urine were collected, body weight was recorded and rectal temperature was measured. The dehydration percentage and sweat rate were the highest at 32 !C and the lowest at 23 !C (23 !C: −0.9±0.5; 27 !C: −1.3±0.6; 32 !C: −2.2±0.7% and 23 !C: 0.48±0.28; 27 !C: 0.76±0.36; 32 !C: 1.25±0.37 l/h). The Post urine volume output was not significantly different in the three trials (23 !C: 122.6±62.4; 27 !C: 78.2±24.9; 32 !C 81.4±37.0 mL). The 27 and 32 !C water increased the rectal temperature (Pre: 37.0±0.3; Post: 37.9±0.5 !C—Pre: 36.9±0.4; Post: 38.0±0.4 !C, respectively).
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Science & Sports (2011) 26, 265—271
ORIGINAL ARTICLE
Effects of three different water temperatures on
dehydration in competitive swimmers
Effets de trois différentes valeurs de température de l’eau sur la
déshydratation chez des nageurs de compétition
F. Macalusoa,,b, V. Di Feliceb, G. Boscainoc, G. Bonsignored, T. Stamponee,
F. Farinab, G. Moricif
aDepartment of Physiological Science, Stellenbosch University, c/o Merriman & Bosman Road, Mike de Vries Building,
Stellenbosch, 7600 South Africa
bDepartment of Experimental Medicine (Di.Me.S.), Section of Human Anatomy ‘‘E. Luna’’, University of Palermo, Palermo, Italy
cDepartment of Statistics and Mathematics ‘‘S. Vinelli’’, University of Palermo, Palermo, Italy
dLaboratory of Transfusion Medicine, Hospital ‘‘Villa Sofia - CTO’’, Palermo, Italy
eLaboratory of Clinical Pathology, Hospital ‘‘Villa Sofia - CTO’’, Palermo, Italy
fDepartment of Experimental Medicine (Di.Me.S.), Section of Human Physiology, University of Palermo, Palermo, Italy
Received 5 May 2009; accepted 5 October 2010
Available online 20 January 2011
KEYWORDS
Open water;
Swimming;
Sweat rate;
Fluid balance;
Performance;
Rectal temperature
Summary
Aims. — The purpose of this study was to evaluate the effects of three different water temper-
atures on physiological responses (dehydration, sweat rate, urine output, rectal temperature
and plasma electrolytes) of competitive athletes during a ‘‘simulated’’ race of 5 km in an indoor
swimming pool.
Methods. — Nine male competitive master swimmers swam 5 km with the water at temperatures
of 23, 27 and 32 C. Immediately before (Pre) and after (Post) each trial, samples of blood and
urine were collected, body weight was recorded and rectal temperature was measured. The
dehydration percentage and sweat rate were the highest at 32 C and the lowest at 23C (23 C:
0.9 ±0.5; 27 C: 1.3 ±0.6; 32 C: 2.2 ±0.7% and 23 C: 0.48 ±0.28; 27 C: 0.76 ±0.36;
32 C: 1.25 ±0.37 l/h). The Post urine volume output was not significantly different in the
three trials (23 C: 122.6 ±62.4; 27 C: 78.2 ±24.9; 32 C 81.4 ±37.0 mL). The 27 and 32 C
water increased the rectal temperature (Pre: 37.0±0.3; Post: 37.9±0.5 C—Pre: 36.9 ±0.4;
Post: 38.0 ±0.4 C, respectively).
Corresponding author.
E-mail addresses: macalusof@sun.ac.za,filippo.mac@libero.it (F. Macaluso).
0765-1597/$ – see front matter © 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.scispo.2010.10.004
266 F. Macaluso et al.
Results. — This study shows that dehydration, sweat rate and body temperatures simultaneously
increase with the rise of water temperature during the shortest open water swimming event
distance (5 km) performed at race intensity.
© 2010 Elsevier Masson SAS. All rights reserved.
MOTS CLÉS
Natation ;
Taux de sudation ;
Équilibre ;
Hydroélectrolytique ;
Performance ;
Température rectale
Résumé
Objectifs. — Évaluer les effets de trois températures différentes de l’eau sur les réponses phys-
iologiques (déshydratation, sudation, volume urinaire, température rectale et électrolytes
plasmatiques) chez des athlètes de compétition, à l’issue d’une course «simulée »de 5 km
dans une piscine couverte.
Méthodes. — Neuf nageurs de compétition (masculins) ont nagé 5 km dans une eau à des
températures respectivement de 23, 27 et 32 C. Immédiatement avant (Pre) et après (Post)
chaque épreuve, des échantillons de sang et d’urine ont été prélevés, la masse corporelle
et la température rectale ont été mesurées. Le pourcentage de déshydratation et le taux de
sudation étaient le plus élevés dans l’eau à 32 C et le plus bas dans l’eau à 23 C (23 C:
0,9 ±0,5 ; 27 C: 1,3 ±0,6 ; 32 C: 2,2 ±0,7%et23
C : 0,48 ±0,28 ; 27 C : 0,76 ±0,36 ;
32 C : 1,25 ±0,37 L/h). Le volume urinaire mesuré après l’effort (Post) n’était pas significative-
ment différent dans les trois cas (23 C : 122,6 ±62,4 ; 27 C : 78,2 ±24,9 ; 32 C 81,4 ±37,0 mL).
Leauà27et32C a augmenté la température rectale (Pre: 37,0±0,3 ; Post : 37,9 ±0,5 C—Pre:
36,9 ±0,4 ; Post : 38,0 ±0,4 C, respectivement).
Résultats. — Cette étude montre que la déshydratation, le taux de sudation et la température
corporelle augmentent simultanément avec la température de l’eau, au cours de la plus courte
des distances parcourues lors de compétitions de nage en eau libre, effectuée avec un effort
d’intensité comparable à celui d’une course.
© 2010 Elsevier Masson SAS. Tous droits réservés.
1. Introduction
Open water swimming is defined, by the Fédération Inter-
nationale de Natation (FINA), as any swimming event that
takes place in a body of water such as rivers, lakes or
oceans [1]. Open water swimming world championships are
performed on distances of 5, 10 and 25 km. During the short-
est (5 km) distance events swimmers are not permitted to
consume food and drink. Open water swimmers perform
races in a wide range of environmental conditions, such
as cold/hot water temperature, high/low water salinity,
high/low altitudes and high/low wave height. Hypothermia
and dehydration are the most common medical problems
during open water events [2,3]. Open water swimming is
a widespread aquatic sport performed also by the master
swimmers globally [4].
Exercise in cold water results in a rapid cooling of the
body, because thermal conductivity is approximately 25
times more than in air [5], and in a raised oxygen uptake
as a consequence of shivering thermogenesis effect [6].
The increase of water temperature and exercise intensity
induces a rise of body temperature [7], although, the heat
exchange occurs mainly via conduction and convection, sub-
stantial amounts of fluid may be lost as sweat during water
sport [8]. Soler et al. [9] reported that during a typical inter-
val training (9 km) in an outdoor pool (water temperature:
27 C), the magnitude of fluid losses (1.8 kg, i.e. 2.5% of body
weight) was sufficient to compromise convective thermoreg-
ulation because of the decreased plasma volume (10.5%),
although the swimmers drank ad libitum. Therefore, if a
negative body fluid balance compromises the thermoregu-
latory and physiological response during swimming training,
this effect may be emphasized during an endurance swim-
ming event. The hypothesis of the present study was that
athletes, swimming the shortest open water swimming world
championship event distance (5 km) without food or drink
supplementation as indicated by FINA rules, may have severe
negative body fluid balance in warm water.
The purpose of this study was to evaluate the effects
of three different water temperatures (23, 27 and 32 C)
on physiological responses (dehydration, sweat rate, urine
output, rectal temperature, plasma electrolytes and fluid
balance) to a ‘‘simulated’’ race of 5 km in competitive ath-
letes in an indoor swimming pool (25 m long).
2. Methods
2.1. Subjects
Nine volunteer male competitive master swimmers, ranked
in the top 5 of category in open water (1.5—10 km) Ital-
ian races, were studied (age: 34.6 ±14.4 years, height:
172.1 ±9.8 cm, mass: 72.7 ±8.5 kg, body fat: 12.7 ±3.5%,
body surface area: 1.86 ±0.16 m2). The subjects trained
five to six times per week (3—8 km per training session)
in 25- and 50-meter swimming pools (water temperature
about 27 C). Participants were informed of the experimen-
tal procedures and associated risk before having to provide a
written informed consent form. This study was approved by
the institutional review board for the protection of human
subjects of the University of Palermo.
2.2. Protocol
During this study, subjects completed three experimental
trials, separated by 7 days, in a 25-meter indoor swimming
pool; they swam 5 km with water at the temperatures of 23,
Effects of three different water temperatures on dehydration in competitive swimmers 267
Table 1 Ambient and water characteristics for each trial.
Ambient Water
Trial (C) Temperature (C) Relative humidity (%) Temperature (C) Chlorine (mg/L) pH
23 30.1 ±1.3 74 ±3 23.3 ±0.3 1.2 7.29
27 27.8 ±1.0 82 ±5 26.8 ±0.2 1.1 7.28
32 28.5 ±1.3 73 ±2 32.0 ±0.4 1.5 7.46
27 and 32 C. The swimming speed of all athletes in each trial
was as close as possible to their personal lactate threshold
speed (data not shown), considered as the swimming speed
at which an athlete produced 4 mmol/L lactate in the blood.
Data were obtained by the swimming club coach. The water
temperatures of the trials were based on Galbo et al. [6],
although the coldest trial was set at 23 C and not at 22 C,
this was due to environmental conditions. The order of the
trials was decided randomly and it was: 23, 32 and 27 C.
Food and fluid were not provided before and during each
trial. Throughout the course of this study, the subjects were
instructed: to consume their regular diet and to repeat a
similar food intake 3 days before each trial; to maintain their
usual training routine and to abstain from vigorous exercise
for at least 24 h before each trial.
The water and ambient characteristics of each trial are
reported in Table 1. This study was designed in the way
that all subjects completed the same trial in the same day,
as they started together a race with the purpose to simu-
late the physiological responses of a race [10]. The athletes
raced in side-by-side swimming pool lanes. Furthermore,
each athlete was free to determine his own swimming pace
during the trials, as in the event of a normal race, with
the purpose to have the specific physiological response of
a race. Although no verbal encouragement was given during
the trials by the investigators, before the trials swimmers
were boastful of who would finish with the best time, which
served as motivation.
2.3. Measurements
The subjects came to the laboratory at 7:00 am of each test
day following an overnight fast (at least 8 hours after the
last drink and meal). First of all, to the subjects were asked
to urinate, and the urine samples were used to measure the
urine specific gravity (USG). Then, they were weighed to
the nearest 25 g (all body weight measurements were taken
with the subjects wearing swimsuit only—Seca 710, Ham-
burg, Germany). After an equilibration time of 15 min in a
sitting posture, blood was drawn from the antecubital vein
to determine haemoglobin (Hgb), hematocrit (Hct), sodium
(Na+), potassium (K+), magnesium (Mg++) concentrations.
Immediately (approximately 60 s on pool deck) before (Pre)
each trial, rectal and axillary temperatures (Tre and Tax,
respectively) [11] were measured with traditional mercury
thermometers set by a medical doctor (rectal thermometer
was inserted 3 cm past the external anal sphincter for 3min;
axillary thermometer was inserted in axillary fossa for 5 min
[12]). Core temperature was not measured.
Immediately (approximately 60 s on pool deck) after
(Post) each trial, rectal and axillary temperatures were mea-
sured again. Then, the urines were collected to measure USG
and total urine volume. The subjects were weighed again at
the end of each trial, after being dried, to measure dehy-
dration percentage. Then, the subjects were asked to sit for
15 min and the Post blood samples were drawn. Only at the
end of each experimental trial the subjects were allowed to
eat and drink.
The blood and urine measurements were performed by
the hematology laboratory of ‘‘Azienda Ospedaliera Villa
Sofia—CTO Palermo’’ with automated analyzers for blood
(Sysmex XE2100, DASIT, Milan, Italy; Dimension RxL Dade
Behring Inc., Newark, DE) and urine samples (Aution Max AX-
4280, A. Menarini Dignostics, Florence, Italy; Sysmex UF100,
DASIT, Milan, Italy). Percentage changes in plasma and red
cell volume, at the end of the three trials, were calcu-
lated using Hct and Hgb concentrations, according to Dill
and Costill [13].
The chronometric time to swim the 5 km and split times
(100 m) was recorded to evaluate the performance. Sweat
rate was calculated using the difference between pre- and
post-exercise body weight divided by the length of trial; it
was not adjusted for body surface area, weight losses asso-
ciated with energy metabolism or respiratory fluid losses
[14].
2.4. Statistics
A two-way ANOVA for repeated measures was performed:
swimming exercise (Pre and Post) versus water tempera-
ture (23, 27 and 32 C). If no interaction but just singular
effect was detected, a one-way ANOVA was performed: this
case concerned urine volume, sweat rate, performance,
body mass loss, plasma and red cell volume. If a signifi-
cant difference was detected during one- or two-way ANOVA
analyses, this was further evaluated by post hoc Duncan’s
multiple-range test (Duncan’s MRT) to determine the ranking
of trial conditions, based on the estimations of the effects on
the variable. The statistical significance was declared when
P< 0.05. The data are expressed as means ±SD. All statisti-
cal procedures were performed using SAS (SAS Institute Inc.
1991).
3. Results
3.1. Body mass change
In all trials, body mass and sweat rate were lost with the
magnitude of these losses being graded by the water tem-
peratures (Fig. 1).
268 F. Macaluso et al.
Figure 1 Hydration status: sweat rate (A) and body weight
loss (B) in response to water temperature. The values are
expressed as means ±SD. Differences between data sets with
the same symbol are significant (P< 0.05). The dotted lines indi-
cate the trendlines for sweat rate and bodyweight.
3.2. Urine output
The Post urine volume output was not significantly dif-
ferent in the three trials (23 C: 122.6 ±62.4; 27 C:
78.2 ±24.9; 32 C 81.4 ±37.0mL). The Post USG concen-
tration decreased in the 23 C (Pre: 1.021 ±0.006; Post:
1.018 ±0.010 g/mL) trial and increased in both 27 (Pre:
1.019 ±0.005; Post: 1.021±0.004 g/mL) and 32 C trials
(Pre: 1.019 ±0.005; Post: 1.021 ±0.004 g/mL). The highest
USG concentration was recorded after the 32 C trial but the
difference did not reach statistical significance by Duncan’s
MRT.
3.3. Rectal and axillary temperature
The measurements of rectal and axillary temperature Pre
and Post trial for each condition are shown in Table 2. The
Post Tre in the 27 and 32C trials was significantly higher
than the other Tre recorded during the experiment; and the
Pre and Post Tre were similar in the 23 C trial. The Post Tax
was significantly higher in the 32 C trial than in the other
Tax recorded during the experiment, and the Pre and Post
Tax were similar in the 23 and 27 C trials.
3.4. Plasma electrolytes
The Post plasma Na+concentration in the 32C trial was sig-
nificantly higher than the other Na+concentration recorded
during the experiment. The Pre and Post 23 C and the Post
32 C plasma Na+concentration were significantly higher
than in Pre and Post 27 C. Statistically analysis indicated
a main effect of swimming exercise on plasma Mg++ concen-
tration, and the main effect of water temperature and
swimming exercise on plasma K+21 concentration. Plasma
electrolytes data are shown in Table 3.
3.5. Fluid balance
Plasma volume increased (Fig. 2A) and the red cell volume
decreased (Fig. 2B) at the end of all three conditions; how-
ever, percentage changes of plasma volume did not differ
between trials. The red cell volume decreased the least in
the 27 C trial than in the 32 C one (P< 0.05).
3.6. Performance time
In the 27 C trial was recorded the best chronometric time
(75.7 ±8.2 min) and split time average (1.51±0.2 min), and
the difference with the 23 and 32 C trials (chronometric
time 79.7 ±11.0 min and 78.5 ±8.7 min respectively; split
time average 1.59 ±0.2 min and 1.57 ±0.2 min respectively)
was significant (P< 0.05), but an ordering effect on perfor-
mance time cannot be excluded.
Table 2 Rectal and axillary temperature.
23C27
C32
C Two-way ANOVA
Pre Post Pre Post Pre Post Pvalue
Tre (C) 37.1 ±0.3 37.2 ±0.6 37.0 ±0.3 37.9 ±0.5a36.9 ±0.4 38.0 ±0.4a0.0001
Tax (C) 36.2 ±0.5 36.0 ±0.6 36.2 ±0.3 36.3 ±0.3 36.3 ±0.3 36.8 ±0.3b0.0022
The values are expressed as means ±SD. Tre (C): rectal temperature; Tax (C): axillary temperature; 23C: trial with the water at
23C; 27C: water at 27C; 32C: water at 32C; Pre: before the trial; Post: after the trial.
aSignificantly higher than other Tre (P< 0.05).
bSignificantly higher than other Tax (P< 0.05).
Effects of three different water temperatures on dehydration in competitive swimmers 269
Table 3 Serum electrolytes.
23C27
C32
C Two-way ANOVA
Pre Post Pre Post Pre Post Pvalue
Na+(mmol/L) 141.0 ±1.4d141.0 ±1.6d136.7 ±2.2 138.5 ±2.7 141.2 ±1.8d144.3 ±1.0c0.0469
K+(mmol/L)a,b 3.8 ±0.3 4.1 ±0.4 4.1 ±0.3 4.4 ±0.3 4.1 ±0.3 4.3 ±0.3 > 0.05
Mg++ (mmol/L)b1.9 ±0.1 1.7 ±0.1 1.9 ±0.1 1.6 ±0.1 1.9 ±0.1 1.7 ±0.1 > 0.05
The values are expressed as means ±SD. Na+: sodium; K+: potassium; Mg++: magnesium; 23C: trial with the water at 23C; 27C: water
at 27C; 32C: water at 32C; Pre: before the trial; Post: after the trial.
aSignificant water temperature main effect from two-way ANOVA (P= 0.0150).
bSignificant swimming exercise main effect from two-way ANOVA (P= 0.0001).
cSignificantly higher than other Na+concentration (P< 0.05).
dSignificantly higher than Pre and Post 27C(P< 0.05).
4. Discussion
The aim of this study was to evaluate the physiological
responses (dehydration, sweat rate, urine output, rectal
temperature, plasma electrolytes and fluid balance) induced
by a 5-km ‘‘simulated’’ race performed at different water
temperatures in an indoor swimming pool.
To date, limited research has been conducted on hydra-
tion status during prolonged swimming training, and, to our
knowledge, no study ever investigated the hydration status
of swimmers after an open water event, although several
general articles have outlined optimal fluid intake for swim-
mers [8]. The reason for the limited number of research on
hydration status of swimmers during competition or training
is the difficulty to control sweat loss. The sources of errors,
detailed described by Cox et al. [8], are: failure to account
for water absorbed through the skin, failure to account
for water accidentally swallowed from the pool, failure to
Figure 2 Fluid balance: changes in plasma (A) and red cell
(B) volume in response to water temperature. The values are
expressed as means ±SD. Differences between data sets with
the same symbol are significant (P< 0.05).
account for respiratory losses, and failure to account for all
urine losses.
Sweat rate during water sports is related to exercise
intensity, core temperature and water temperature [8,9].In
our study, the athletes swam the 5 km of each trial at their
personal highest intensity, as they would in a race, although
the best performance was recorded during the 27 C trial,
confirming the results in literature [15]. Therefore, the dif-
ference recorded in the sweat rate and in the body (axillary
and rectal) temperature are purported to be induced exclu-
sively by the water temperature, although, we acknowledge
that axillary and rectal temperature measured with tradi-
tional mercury thermometers may have some limitations
[11].
The 23 C water, during swimming at high intensity, was
a thermoneutral environment because of slow sweat rate
(0.48 L/h) that did not raise body temperature inducing light
dehydration (0.9%, 0.65 kg). The 32C water increased the
axillary and rectal temperatures, the 27 C trial increased
the rectal temperature only, confirming results in liter-
ature, which showed that the increasing temperature of
water combined with exercise intensity induces a rise of
core and rectal temperatures [5—7]. None of the subjects
were affected by hypothermia at the end of the three tri-
als, although it is common in swimmers competing in an
open water swimming event [2,3,16—18]. Thereby, the 27
and 32 C water induced a fast sweat rate (0.76 L/h and
1.25 L/h respectively) that compromised the hydration sta-
tus of swimmers (1.3%, 0.94 kg and 2.2%, 1.60 kg,
respectively). These results show that dehydration can occur
rapidly in swimmers that compete in a 5-km race in 32 C
water and slower in colder water. These results are in con-
trast with the data of several articles, recorded during
swimming training in 27 C water. Lemon et al. [18] observed
that an interval swim training of 62 min, without fluid intake,
produced a body weight reduction of 0.6 kg and a sweat rate
of 0.48 L/h. These results were corrected for weight gain
due to uptake of water by the skin and for respiratory and
metabolic losses. A similar body weight reduction (0.7 kg)
is reported by Reaburn et al. [19] after a 4.7-km training
session with no fluid intake. The lowest results are reported
by Cox et al. [8], Maughan et al. [20] and Soler et al. [9]
(0.11%, 0.41 L/h; 0.3%, 0.33 L/h and 0%, 0.37 L/h, respec-
tively), although the training sessions were longer and the
swimmers drank ad libitum. Similar sweat rate (1.07 L/hr)
at 33C water were found in a study of Robinson and Somers
270 F. Macaluso et al.
[21], although it was carried out only on two subjects,
olympic-medal-winning swimmers, during a 60-min freestyle
training session at a high speed of about 1.2 m/s.
It is widely accepted that plasma aldosterone levels are
linearly related to exercise intensity and heat exposure [22]
and, even if hormone concentration was not tested during
this study, we suppose that water loss and hyperosmolality
induced by swimming in hot water would stimulate aldos-
terone secretion. Aldosterone in turn increases Na+uptake
and consequently water retention in the distal tubules of
nephrons. Our theory is confirmed by the data recorded:
the Post urine output in the 27 and 32C trials, were more
concentrated than in the 23 C ones, in fact, both the warm
trials induced lower urine volume, higher USG concentra-
tion than in the 23 C trial. Furthermore, sodium and water
re-absorption, stimulated by exercise in all three condi-
tions, determined hypernatremia and hypervolemia, i.e. an
increasing of plasma sodium concentration and an expand-
ing of extracellular water. In fact, the percentage change
of plasma volume increased in all three trials and the per-
centage change of red cell volume decreased in all three
water conditions, showing the fluid shift from the intra-
cellular space to the extracellular space to prevent the
decline in plasma volume induced by the dehydration [23].
We acknowledge that USG is normally used as an indicator
of longitudinal hydration status during chronic studies, and
it may have some limitation to hydration status in an acute
study [24]. Although, the plasma volume change has been
already investigated in swimmers with the method of Dill
and Costill [13] by Soler et al. [9], this technique should have
a limitation related to equilibration period used before the
blood draw. In this study, an equilibration period of 15 min
was used to minimize the error source, while, Soler et al.
[9] did not used an equilibration period before drawing the
blood.
Our study provides unique information on the effects
induced by water temperature during an open water swim-
ming race on sweat rate and dehydration percentage,
because this study is the first study conducted for open
water swimmers during swimming, and not during under
water exercise, at race intensity [19]. The results of this
study show that during the shortest open water swimming
event distance (5 km) performed at race intensity: (i) the
dehydration and the sweat rate incurred in 27C water are
greater than that reported in swimming-training studies; (ii)
the dehydration and the sweat rate and body temperatures
simultaneously increase with the rise of water temperature.
Conflict of interest statement
None.
Acknowledgments
We thank the athletes who participated in the study and
the coach Salvo Caleca for help in data collection. We thank
Mrs M. Moyen and A.W.Isaacs (Department of Physiological
Science, Stellenbosch University, South Africa) for reading
and commenting on our paper.
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... Although there has been significant scientific research into the consequences of hot environmental conditions on athletes' health and performance during terrestrial sporting activities and the development of subsequent large-scale protective guidelines (Armstrong et al., 2007), comparatively little attention has been paid to the safety and performance implications of competing in hot aquatic environments (Macaluso et al., 2011;Hue et al., 2013Hue et al., , 2015. Similar to cases in terrestrial sports during hot and humid conditions (Gamage et al., 2020), aquatic competition in high-risk conditions can have tragic consequences. ...
... A high metabolic rate (oxygen consumption [VȮ 2 ] often exceeding 3.2 l/min at typical competition pace [Holmér, 1972;Toussaint et al., 1990;Zacca et al., 2020]) is also evident in elite open-water swimmers for long durations (≥60 min). Moreover, prolonged swimming in warm water is associated with elevated sweat rates (often exceeding 1 l/h; Macaluso et al., 2011;Hue et al., 2013). Elevated skin temperature during warm water swimming (Costill et al., 1967;McMurray and Horvath, 1979) is accompanied by a peripheral vasodilatory response, creating further competition for blood volume with the contracting muscles (Sawka et al., 2011). ...
... Conversely, a high core temperature response to exercise increases the risk of exertional heat illness (Armstrong et al., 2007). Some published reports suggest that rectal (T re ) and gastrointestinal (T gi ) temperature may not be consistently dangerous during simulated 5 km performance in T w of 32.0°C (end-event T re of 38.0°C; Macaluso et al., 2011) and competitive 10 km performance in T w of 28.1°C (end-event T gi 38.3°C; Hue et al., 2015), with either none or very little in-race cold fluid consumption. Bradford and colleagues (Bradford et al., 2013) reported that the end-event T re during a simulated 120 min (similar duration to a 10 km event) swim in 32°C water was on average, 38.4°C for 22 competitive swimmers. ...
Article
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Open-water swim racing in warm water is associated with significant physiological strain. However, existing international policy that governs safe participation during competition relies only on a fixed water temperature threshold for event cancellation and has an unclear biophysical rationale. The current policy does not factor other environmental factors or race distance, nor provide a stratification of risk (low, moderate, high, or extreme) prior to the threshold for cancellation. Therefore, the primary aim of this Perspectives article is to highlight considerations for the development of modernized warm-water competition policies. We highlight current accounts (or lack thereof) of thermal strain, cooling interventions, and performance in warm-water swimming and opportunities for advancement of knowledge. Further work is needed that systematically evaluate real-world thermal strain and performance during warm water competition (alongside reports of environmental conditions), novel preparatory strategies, and in-race cooling strategies. This could ultimately form a basis for future development of modernized policies for athlete cohorts that stratifies risk and mitigation strategies according to important environmental factors and race-specific factors (distance).
... Changes from pre-surf values indicated that 30% of USG values increased, 30% stayed the same, and 40% decreased. Current literature on hydration status changes by Macaluso et al. (11) and Walker et al. (22) found similar inconsistencies with USG data when compared to BM data results. ...
... Current literature suggests urine specific gravity is only reliable for chronic dehydration and should only be used for pre-testing (11,15,22) Our findings varied to the above findings due to the subjects showing limited changes in USG after surfing compared to pre-surfing. With 40% of the subjects already in a moderately dehydrated state (USG > 1.020) prior to the 2-hour surfing session, and the variability in the post-surfing USG being sizable possibly attributable to the large proportion of subjects already in a dehydrated state. ...
Article
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Surfing is a popular sport globally which is performed in varied environmental conditions. With limited research in the field exploring hydration, monitoring the effect of surfing on subject hydration is warranted. The purpose of this study was to determine the relationship between surfing intensity and hydration status. A total of ten recreational male surfers were recruited for this study where hydration status was assessed pre-and post-surf session by measures of body mass (BM) and urine specific gravity (USG). Intensity of the surf session was quantified by Global Positioning Systems and Heart Rate monitoring. Subjects surfed for two hours and covered an average distance of 4974.18 ± 542.62 m, with an average speed of 2.48 ± 0.27 km/h and peak speed of 31.86 ± 3.51 km/h. A statistically significant decrease in absolute and relative BM was observed (0.70 ± 0.4 kg, p < 0.05 & 0.86 ± 0.54%, p < 0.001, respectively). No statistically significant correlation was found between variables (total distance paddled and relative BM, r = 0.432, p = 0.245; average HR and relative BM change, r = -.246, p = 0.595). Total distance paddled combined with average HR significantly predicted relative body mass change (F(2,3) = 29.362, p = 0.011, adjusted R 2 = 95.1%). The results demonstrate that a 2-hour recreational surfing session, in temperate environmental conditions, without neoprene garments resulted in minimal BM changes and no changes in USG. Surfers who paddle a greater distance at a higher average HR sustained greater BM changes.
... The upper temperature limit with only a swimsuit has been based on limited evidencebased research. Macaluso et al. (2011), Macaluso et al. (2013), demonstrated that swimming a 5 K in a pool at 32 °C (89.6°F) raised Tcore by 2°C up to about 39.7°C, in 30 min of exercise. Fujishima et al. (2001) after a longer swim of 120 min at 50% of VO2 max observed that Tcore between 23 and 28 °C dropped by −1°C. ...
Article
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The aim of this study was to investigate the effect of prolonged steady state swimming with a wetsuit, on thermoregulatory and behavioural responses, in water of 25°C. Ten male swimmers participated in two 75-min swim trials, in one wearing a neoprene wetsuit (WS), and the other a conventional swimsuit (SS). The swimming intensity was controlled at 70% of swimmers’ critical velocity (CV). Core (Tcore) and skin (Tsk) temperature, heart rate (HR), and behavioural modulators, were measured before, during and after swimming. A 2-way ANOVA for repeated measures with aFisher’s 2SD test was used for multiple comparisons and a paired t-test with a Tukey post hoc analysis for pre and post measurements at p< 0.05. The results demonstrated an interaction of Tcore (p = 0.039), between time in the water and type of garment worn. Tcore with the WS initially increased until the 45th min and plateaued, while with the SS was continuously decreasing. HR was lower during swimming with the WS and higher with the SS. Thermal sensation and thermal comfort, were more favourable with the WS (p < 0.05). Thus, WS use during prolonged swimming, helped maintain Tcore levels, and improved thermal perceptions, at 25 °C.
... Surfing can be accomplished in a variety of climates, ranging from arctic to tropical, with the reported intensity of surf practice being between 70-80% peak heart rate (9,12) and participation of up to 5 hours (12). Although heat exchange in water sports occurs mainly through conduction and convection, increases in water temperature and exercise intensity induce a rise in body temperature, which can result in substantial fluid loss through sweating (7). In addition, surfers wear wetsuits to reduce convective heat loss due to cold-water exposure (21). ...
Article
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Surfing offers unique challenges to thermoregulation and hydration. The purpose of this study was to quantify fluid loss in recreational surfers, and to analyze the effects of water temperature, air temperature, exercise intensity, duration, and garment thickness on the total amount of fluid lost during a surf session. A total of 254 male and 52 female recreational surfers were recruited from San Diego, Costa Rica, and Australia to participate in the study. Participants’ hydration status was assessed by comparing nude body mass pre- and post-surf session. Heart rate (HR), used as an index of exercise intensity, was measured throughout the session. Environmental conditions and surf characteristics were recorded. The difference between average pre-mass (73.11 ± 11.88 kg) and average post-mass (72.51 ± 11.78) was statistically significant (0.60 ± 0.55, p < 0.001). Surfers experienced a 0.82 ± 0.73% reduction in body mass. In multivariable linear regression, session duration and body mass index (BMI) were significantly associated with fluid loss. For every 10- minute increase in session duration, there was a 0.06 kg (SE = 0.001; p < 0.001) increase in fluid loss, and for every two unit increase in BMI, fluid loss increased by 0.05 kg (SE = 0.03; p = 0.02). Results suggest that prolonged surfing at high environmental temperatures in participants with high BMI’s resulted in significant body water deficits. Since there is no opportunity to rehydrate during a surf session, surfers must properly pre-hydrate before surfing in order to avoid the detrimental effects of dehydration.
... We obtained SR data from 14 open literature studies (Table 1) [12][13][14][15][16][17][18][19][20][21][22][23][24][25], which included 20 separate group means, where group sizes ranged from 7 to 27 subjects. One study involved walking, while 5 independent studies looked at cycling, 4 at swimming, and 4 at soccer match play. ...
Article
This study tested the accuracy of a novel, limited-availability web application (H2Q™) for predicting sweat rates in a variety of sports using estimates of energy expenditure and air temperature only. The application of predictions for group water planning was investigated for soccer match play. Fourteen open literature studies were identified where group sweat rates were reported (n = 20 group means comprising 230 individual observations from 179 athletes) with fidelity. Sports represented included: walking, cycling, swimming, and soccer match play. The accuracy of H2Q™ sweat rates was tested by comparing to measured group sweat rates using the concordance correlation coefficient (CCC) with 95% confidence interval [CI]. The relative absolute error (RAE) with 95% [CI] was also assessed, whereby the mean absolute error was expressed relative to an acceptance limit of 0.250 L/h. The CCC was 0.98 [0.95, 0.99] and the RAE was 0.449 [0.279, 0.620], indicating that the prediction error was on average 0.112 L/h. The RAE was < 1.0 for 19/20 observations (95%). Drink volumes modeled as a proxy for sweat losses during soccer match play prevented dehydration (< 1% loss of body mass). The H2Q™ web application demonstrated high group sweat prediction accuracy for the variety of sports activities tested. Water planning for soccer match play suggests the feasibility of easily and accurately predicting sweat rates to plan group water needs and promote optimal hydration in training and/or competition.
Thesis
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The impact of environmental conditions on exercise performance in elite athletes has been explored extensively in the laboratory. Research is yet to determine the effect of the environment on performance in applied settings and novel non-thermally mediated ergogenic aids for endurance exercise in the heat have recently been proposed but are poorly understood and have not been tested in an endurance trained population. The studies in this thesis determined the effect of divergent environmental conditions on outdoor swimming performance in elite swimmers and the effect of paracetamol on the performance of trained triathletes during an endurance cycling bout in hot and humid conditions. There was no effect of the environmental conditions on the core temperature or performance of elite swimmers but skin temperature and thermal sensation differed between conditions. Paracetamol had no effect on endurance time trial performance and core and skin temperature, heart rate and thermal perception was unaffected during steady state and time trial cycling. Overall, the findings reiterate the importance of assessing thermal stress and ergogenic aids in ecologically valid settings using well planned applied study designs. Thermal stress was found to be specific to exercise mode, environmental conditions and exercise intensity and trained endurance athletes should continue to use thermally mediated pre- and per-cooling methods as non-thermally mediating ergogenic aids may not reduce core and skin temperature or thermal perception effectively during endurance exercise bouts.
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Swimming is one of the most popular sports in the world with open-water swimming (OWS) gaining more and more prominence since being featured in the Federation Internationale De Natation World Aquatics Championships in 1992 and the Olympic Games in 2000. The aim of this review is to analyze the existing literature on heat injury in OWS. Relevant literature was located via computer-generated citations during November of 2020 through online computer searches of multiple major databases. Athletes participating in OWS are exposed to environmental conditions that place them at risk for unique medical conditions such as heat injury. Clinicians providing care for OWS athletes should be educated and trained to recognize these conditions and minimize risks to optimize athlete safety. This article identifies medical challenges related to heat injury in OWS while investigating water temperature recommendations, physiological effects of hyperthermia, risk mitigation strategies, and treatment measures.
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The Investigation of Fluid Loss in Different Endurance Training Abstract The aim of this study is to examine the effects of endurance training in two different environments (land and water) on the amount of body fluid. 16 male athletes who have taken swimming training voluntarily participated in this study [(mean ± SD) age: 20.06 ± 1.91 years; height: 178.06 ± 7.84cm; body weight: 72.87 ± 6.91kg; body fat percentage: 9.94 ± 3.18]. In the study, the athletes were randomly divided into 2 equal groups (8 land training groups, 8 underwater exercise groups) and a total of 2 hours of endurance training was applied with 15 minutes of warm-up. In the study, after the first applications were completed, a break was given for 24 hours, after which the land training group applied in-water exercise and the in-water exercise group applied land training. In the meantime, body composition measurements (body weight, body fluid amount, muscle mass, body fat percentage), urine density and body temperature were measured before and just after the two-hour endurance training. For the statistical analysis paired sample t-test was used. As a result of the statistical analysis, it was determined that there was a significant difference in body weight, body fluid amount, muscle mass, body fat percentage and body temperature (p <0,05), but there was no statistically significant difference in urine density (p> 0,05). As a result, it was determined that there are statistically significant changes in body fluid amount, muscle ratio and body temperature values in endurance exercises performed in both environments. Keywords: Endurance, Dehydration, Urine specific gravity, Body composition
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Öz Yapılan bu çalışmanın amacı iki farklı ortamda yapılan (karada ve suda) dayanıklılık antrenmanının vücut sıvı miktarı üzerine etkilerinin incelenmesidir. Bu çalışmaya yüzme eğitimi almış [(𝑋̅ + 𝑠𝑠) yaş: 20,06±1,91 yıl; boy: 178,06±7,84cm; vücut ağırlığı: 72,87± 6,91kg; vücut yağ yüzdesi: 9,94±3,18] olan 16 erkek sporcu gönüllü olarak katılmıştır. Çalışmada sporcular rastgele örneklem seçim yöntemi ile 2 eşit gruba ayrılmış (8 kara antrenmanı gurubu, 8 su içi egzersiz grubu) ve 15 dakikalık ısınma ile birlikte toplam 2 saat dayanıklılık antrenmanı uygulamıştır. Çalışmada ilk uygulamalar tamamlandıktan sonra 24 saat ara verilmiştir. Sonrasında kara antrenman grubu su içi egzersiz, su içi egzersiz grubu ise kara antrenmanı uygulamıştır. Bu esnada iki saatlik dayanıklılık antrenmanı öncesi ve hemen sonrası vücut kompozisyonu ölçümleri (vücut ağırlığı, vücut sıvı miktarı, kas kütlesi vücut yağ yüzdesi), idrar yoğunluğu ve vücut sıcaklığı ölçümleri yapılmıştır. İstatistiksel analizlerde eşleştirilmiş örneklerde t-testi kullanılmıştır. Yapılan istatistiksel analiz sonucunda vücut ağırlığı, vücut sıvı miktarı, kas kütlesi, vücut yağ yüzdesi ve vücut sıcaklığı değerlerinde anlamlı fark olduğu (p<0,05), idrar yoğunluğunda ise istatistiksel olarak anlamlı bir fark olmadığı (p>0,05) belirlenmiştir. Sonuç olarak her iki ortamda da yapılan dayanıklılık egzersizlerinde vücut sıvı miktarı, kas oranı ve vücut sıcaklığı değerlerinde istatistiksel olarak önemli değişiklikler olduğu tespit edilmiştir. Anahtar kelimeler: Dayanıklılık, Dehidrasyon, İdrar yoğunluğu, Vücut kompozisyonu. The Investigation of Fluid Loss in Different Endurance Training Abstract The aim of this study is to examine the effects of endurance training in two different environments (land and water) on the amount of body fluid. 16 male athletes who have taken swimming training voluntarily participated in this study [(mean ± SD) age: 20.06 ± 1.91 years; height: 178.06 ± 7.84cm; body weight: 72.87 ± 6.91kg; body fat percentage: 9.94 ± 3.18]. In the study, the athletes were randomly divided into 2 equal groups (8 land training groups, 8 underwater exercise groups) and a total of 2 hours of endurance training was applied with 15 minutes of warm-up. In the study, after the first applications were completed, a break was given for 24 hours, after which the land training group applied in-water exercise and the in-water exercise group applied land training. In the meantime, body composition measurements (body weight, body fluid amount, muscle mass, body fat percentage), urine density and body temperature were measured before and just after the two-hour endurance training. For the statistical analysis paired sample t-test was used. As a result of the statistical analysis, it was determined that there was a significant difference in body weight, body fluid amount, muscle mass, body fat percentage and body temperature (p <0,05), but there was no statistically significant difference in urine density (p> 0,05). As a result, it was determined that there are statistically significant changes in body fluid amount, muscle ratio and body temperature values in endurance exercises performed in both environments. Keywords: Endurance, Dehydration, Urine specific gravity, Body composition.
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Problem: Hydration is considered as one of the most important nutritional ergogenic aids. However, there are very few coaches and athletes in Colombia who really focus on fulfill this requirement. Actually, those who know or were instructed about the importance of being well hydrated, only try to accomplish the fluid intake during competitions or training sessions, disregarding the moment before and after each sports / training event. Objective: The aim of this research was to describe the water balance levels of swimmers belonging to the Club Orcas Tuluá, Colombia. Methodology: Eight young swimmers (men = 6; women = 2; age = 13.8 ± 1.4 years) participated in this descriptive study. After being advised of the experiment and asked to sign an informed consent form (parent/guardian), the following variables were measured in all subjects during 7 days: pre-and post-training weight, length of training, volume of fluid intake during exercise, and self-perceived hydration was assessed using the urine color eight-point Armstrong scale at four time points. Results: Our results showed a mean pre-exercise body mass of 58.0 kg while mean post-exercise value was 56.8 kg, which lead to a 2.06% hypohydration status in the group of young swimmers. After calculation mean body water loss and sweat rate was 1.88 L·h-1 and 0.73 L·h-1 , respectively. The athletes were placed at a level 4 of hydration classification, which corresponds to not sufficiently hydrated. Interestingly, hypohydration status and post-exercise body mass change were less in female athletes in comparison to male. Conclusion: Even though studied athletes consumed water or isotonic drinks during exercise, they do not hydrate properly throughout the day. Based on these results we establish some easy-to-understand and practical recommendations for coaches, family and young athletes to improve hydration status in Colombian population.
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Open water swimming is a rapidly growing discipline within organized aquatic sport. Although endurance swimmers have been challenged by oceans, rivers, and lakes for many years, the real understanding of the science of the sport is a new phenomenon. Similarly, the clinical problems of long-distance swimming in environments, frequently inhospitable, are now recognized and managed more effectively. At all times, the health and safety of athletes remains a shared prime concern. By definition, open water swimming implies any event held outside the confines of a swimming pool. Over the past 30 years, there has been a proliferation of such events in lakes, rivers, reservoirs, and on ocean courses, particularly in temperate countries where water temperatures are more welcoming. This article discusses the development of open water swimming as an international sport, describing its history, characteristics, and some factors that affect the performance of the open water swimmer. Particular emphasis will be placed on issues of special medical importance. The first of several formal competitions in open water swimming was surf lifesaving, a competitive activity common to New Zealand, Australia, the west coast of the United States, and South Africa. Surf races are held over distances ranging from 300 to 1000 m. Competitors run from the beach into the surf, swim clockwise around a row of eight buoys, anchored behind the surf break, and return directly to the beach where they finish by running between two flags. The advent of the triathlon in the early 1970s stimulated a rapid growth in the popularity of mass-participation, open water events for multisport competitions. These events have lead to an increased regard for the safety of participants and a greater understanding of the demands of open water swimming. The medical supervision of such events continues to challenge aquatic sports medicine experts who must consider the safety of the athlete as their first priority.
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Analysis of injury and illness prevalence in elite sport provides the basis for the development of prevention programmes. To analyse the frequency and characteristics of injuries and illnesses occurring during the 13th Federation Internationale de Natation (FINA) World Championships 2009. Prospective recording of newly incurred injuries and illnesses. The 13th FINA World Championships hosted 2592 athletes from 172 countries in the disciplines of swimming, diving, synchronised swimming water polo and open water swimming. All team physicians or physiotherapists were asked to complete daily a standardised reporting form for all newly incurred injuries and illnesses for their teams. To cover teams without medical staff, the physicians of the Local Organizing Committee also submitted daily report forms. 171 injuries were reported resulting in an incidence of 66.0 per 1000 registered athletes. The most affected body parts were the shoulder (n=25; 14.6%), and head (n=21; 12.3%). Half of the injuries occurred during training. The most common cause of injury was overuse (n=61; 37.5%). 184 illnesses were reported resulting in an incidence of 71.0 per 1000 registered athletes. The respiratory tract was most commonly affected (n=91; 50.3%) and the most frequently classified cause was infection (n=81; 49.2%). The incidence of injuries and illnesses varied substantially among the five disciplines, with the highest incidence of injury in diving and the lowest in swimming. As the risk of injury varied with the discipline, preventive measures should be discipline specific and focused on minimising the potential for overuse. As most of the illnesses were caused by infection of the respiratory and gastrointestinal tract, preventive interventions should focus on eliminating common modes of transmission.
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There are no available data addressing the potential clinical risks of open-water swimming competitions. Address the risks of hypothermia and hypoglycemia during a 10-km open-water swimming competition in order to alert physicians to the potential dangers of this recently-introduced Olympic event. This was an observational cross-sectional study, conducted during a 10-km open-water event (water temperature 21 degrees C). The highest ranked elite open-water swimmers in Brazil (7 men, 5 women; ages 21+/-7 years old) were submitted to anthropometrical measurements on the day before competition. All but one athlete took maltodextrine ad libitum during the competition. Core temperature and capillary glycemia data were obtained before and immediately after the race. Most athletes (83%) finished the race with mild to moderate hypothermia (core temperature <35 degrees C). The body temperature drop was more pronounced in female athletes (4.2+/-0.7 degrees C vs. male: 2.7+/-0.8 degrees C; p=0.040). When data from the athlete who did not take maltodextrine was excluded, capillary glycemia increased among athletes (pre 86.6+/-8.9 mg/dL; post 105.5+/-26.9 mg/dL; p=0.014). Time to complete the race was inversely related to pre- competition body temperature in men (r=-0.802; p=0.030), while it was inversely correlated with the change in capillary glycemia in women (r=-0.898; p=0.038). Hypothermia may occur during open-water swimming events even in elite athletes competing in relatively warm water. Thus, core temperature must be a chief concern of any physician during an open-water swim event. Capillary glycemia may have positive effects on performance. Further studies that include more athletes in a controlled setting are warranted.
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To assess the hydration status and level of hydration knowledge of youths at summer sports camps. Sixty-seven active youths, 57 males (mean +/- SD, 12 +/- 2 y, 136 +/- 16 cm, 50.6 +/- 21.1 kg) and 10 females (13 +/- 2 y, 153 +/- 8 cm, 45.2 +/- 9.0 kg) participated in 4 d of sports camp. Hydration status was assessed before the first practice (AM) and after the second practice (PM). Participants completed surveys assessing hydration knowledge (HAQ) and hydration habits on day 3 and a self-assessment (EQ#1). Mean AM urine specific gravity (USG) and urine osmolality (Uosm) scores ranged from minimal to significant dehydration across 4 d, even when temperatures were mild. Correlations between hydration indices and EQ#1, ranging from 0.11 to -0.51, were statistically significant (P < .05), indicating that subjects recognized when they were doing a good or bad job hydrating. HAQ did not correlate strongly with hydration indices suggesting other impediments to hydration. Thirst correlated negatively with EQ#1 (from -0.29 to -0.60). Hydration at summer sports camp is a concern and special efforts need to be made to help youths develop hydration strategies.
Book
Written at a graduate level, the Second Edition of ACSMs Advanced Exercise Physiology enables experienced students to develop an in-depth understanding of exercise physiology along with its related topics and applications. Both the immediate and long-term effects of exercise on individual body systems are described in detail, and the text emphasizes how each body systems physiological response to exercise is interdependent. Moreover, it examines how these physiological responses are affected by heat, cold, hypoxia, microgravity, rest, and hyperbaria. This Second Edition features a team of international authors and editors whose expertise spans general physiology, exercise physiology, and research. Together, they have substantially revised, updated, and reorganized the text to incorporate feedback from both instructors and students. © 2012 American College of Sports Medicine. All rights reserved.
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This study investigated fluid and electrolyte balance in well-trained male and female swimmers during 2 training sessions. Participants were 17 nationally ranked swimmers measured during a period of intensive training. Sweat loss was assessed from changes in body mass after correction for fluid intake and urine collection. Sweat composition was measured from waterproof absorbent patches applied at 4 skin sites. Air and pool-water temperatures were 36 degrees C and 27.4 degrees C, respectively. Training lasted 105 min in each session. All measured variables were similar on the 2 testing days. Mean sweat-volume loss was 548 +/- 243 ml, and mean sweat rate was 0.31 +/- 0.1 L/hr. Mean fluid intake was 489 +/- 270 ml. Mean body-mass loss was 0.10 0.50 kg, equivalent to 0.1% +/- 0.7% dehydration. Mean pretraining urine osmolality was 662 +/- 222 mOsm/kg, which was negatively associated with both mean drink volume consumed (p = .044, r = .244) and mean urine volume produced during training (p = .002, r2 = .468). Mean sweat Na+, K+, and Cl- concentrations (mmol/L) were 43 +/- 14, 4 +/- 1, and 31 +/- 9, respectively; values were not different between males and females and were not different between days except for a marginal difference in K+ concentration. The average swimmer remained hydrated during the session, and calculated sweat rates were similar to those in previous aquatic studies.
Article
To document the prevalence of hypothermia in a mass participation endurance open water swimming event and to determine demographic and individual factors that may predict failure to finish the race and hypothermia. A prospective observational study in competitors in a 19.2-km open water swimming race in Perth, Western Australia. Pre-race information collected included age, sex, training and race experience, medical history, and body mass index (BMI). Body temperatures at 5 minutes postrace were measured using an equilibrated oral- or rectal-reading low-range glass mercury thermometer. Logistic regression was used to develop models predicting hypothermia (defined as a temperature of <35 degrees C) and failure to finish the race. One hundred and nine competitors (70 male, 39 female) with a combined mean age of 38.4 +/- 12.1 years were studied. Hypothermia was the most common race-related illness, identified in 26 of 35 swimmers screened as requiring temperature measurement, including 5 who required short-stay hospital care and 2 who required critical care transfer. Longer race duration (odds ratio [OR] 1.77, 95% CI 1.10-2.84, P = .018) was associated with an increased risk of hypothermia, and higher BMI (OR 0.57, 95% CI 0.41-0.79, P = .001) was associated with a decreased risk of hypothermia. Weak predictors of failure to finish were age (OR 1.06, 95% CI 1.01-1.11, P = .012) and hours spent training (OR 1.08, 95% CI 1.01-1.16, P = .025). Hypothermia is a common condition affecting mass participation long-distance open water swimmers. Increased BMI appears to be protective against hypothermia, while prolonged duration of the swim predicts an increased risk of hypothermia. The weak predictors of failing to finish are of questionable clinical significance.
Article
The relationship between thermoreception, hormonal secretion and muscular activity was studied. 6 men swam 60 min in 21, 27 and 33 degrees C water at a speed requiring 68% of VO2 max (determined in 27 degrees C water). Rectal temperature increased in 33 degrees C (1.3 +/- 0.2 degrees C, mean and S.E.) and 27 degrees C (0.7+/- 0.1 degrees C) expts. but decreased in 21 degrees C expts. (0.8 +/- 0.3 degrees C). Changes in esophageal and muscle temperatures parallelled changes in rectal temperature. Plasma noradrenaline was higher in 33 degrees C than in 27 degrees C expts. and growth hormone, cortisol and glucagon concentrations increased in 27 degrees C and 33 degrees C expts. only. Insulin concentrations were uniformly depressed during swimming at the different water temperatures. In 21 degrees C expts. noradrenaline and adrenaline concentrations were higher than in 27 degrees C expts. VO2, carbohydrate combustion and peak lactate were slightly lower in 33 degrees C expts. Plasma glucose decreased slightly and FFA and glycerol concentrations increased identically in all expts. Heart rate increased continuously during swimming in 27 degrees C and 33 degrees C expts., but not in 21 degrees C expts. In conclusion the rise in body temperatures normally observed during exercise enhances the exercise induced increases in the plasma concentrations of noradrenaline, cortisol, growth hormone and glucagon. Decreased body temperatures may elicit catecholamine secretion as a direct consequence of thermoreception. Shivering may account for previously observed decreases in insulin secretion during cold stress but not for increases in cortisol and growth hormone.
Article
Male interscholastic swimmers (n = 8) completed a 4572 m training swim in in 62 +/- 1.1 min (means +/- S.E.) with terminal heart rate and blood lactate of 152 +/- 6 beats min-1 and 6.9 +/- 0.89 mM, respectively. Sweat rate (0.48 +/- 0.095 l. h-1) was lower than similar intensity cycling (1.5 +/- 0.13 l. h-1) or running (1.1 +/- 0.14 l. h-1). Post-swim serum urea N (11.6 +/- 0.71 mM) was elevated (P less than 0.05) vs pre-swim (4.6 +/- 0.39 mM). Post-swim urine volume (860 +/- 75 ml 24 h-1) was reduced (P less than 0.07) and resulted in an elevated (P less than 0.05), but delayed (24-84 h), post-exercise urea N excretion. Although the reduced urine and sweat production during the swim undoubtedly contributed to the elevated serum urea, there must be another explanation because together they could only account for 38% of the observed increase. On the basis of the magnitude of serum urea increase, it appears that the swim caused an increase in urea production (amino acid oxidation). The failure to observe larger increases in urinary urea during recovery indicates that either urea excretion following exercise continues for prolonged periods of time (greater than 48 h) or another significant mode of nitrogen excretion exists.
Article
Observations on hematocrit (Hct) and hemoglobin (Hb) were made in 6 men before and after running long enough to cause a 4% decrease in body weight. Subscripts B and A were used to denote before dehydration and after dehydration, respectively. Relations were derived between BV(b), BV(a), HB(b), Hb(a), Hct(b), and Hct(a) with which the percentage decreases in BV, CV, and PV can be calculated, as well as the concentration of hemoglobin in red cells, g/100 ml-1 (MCHC). When subjects reach the same level of dehydration the water loss from the various body compartments may vary reflecting the difference in salt losses in sweat. Changes in PV calculated from the increase in plasma protein concentration averaged -7.5% compared with -12.2% calculated from changes in Hb and Hct. The difference could be accounted for by a loss of 6% plasma protein from the circulation.