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Analysis of Dehydration and Strength in Elite Badminton
Players
Javier Abia
´
n-Vice
´
n, Juan Del Coso, Cristina Gonza
´
lez-Milla
´
n, Juan Jose
´
Salinero, Pablo Abia
´
n*
Exercise Physiology Laboratory, Camilo Jose
´
Cela University, Madrid, Spain
Abstract
Background:
The negative effects of dehydration on aerobic activities are well established. However, it is unknown how
dehydration affects intermittent sports performance. The purpose of this study was to identify the level of dehydration in
elite badminton players and its relation to muscle strength and power production.
Methodology:
Seventy matches from the National Spanish badminton championship were analyzed (46 men’s singles and
24 women’s singles). Before and after each match, jump height and power production were determined during a
countermovement jump on a force platform. Participants’ body weight and a urine sample were also obtained before and
after each match. The amount of liquid that the players drank during the match was also calculated by weighing their
individual drinking bottles.
Results and Discussion:
Sweat rate during the game was 1.1460.46 l/h in men and 1.0260.64 l/h in women. The players
rehydrated at a rate of 1.1060.55 l/h and 1.0160.44 l/h in the male and female groups respectively. Thus, the dehydration
attained during the game was only 0.3760.50% in men and 0.3260.83% in women. No differences were found in any of the
parameters analyzed during the vertical jump (men: from 31.8265.29 to 32.9064.49 W/kg; p.0.05, women: from
26.3664.73 to 27.2564.44 W/kg; p.0.05). Post-exercise urine samples revealed proteinuria (60.9% of cases in men and
66.7% in women), leukocyturia (men = 43.5% and women = 50.0%) and erythrocyturia (men = 50.0% and women = 21.7%).
Conclusions:
Despite a moderate sweat rate, badminton players adequately hydrated during a game and thus the
dehydration attained was low. The badminton match did not cause muscle fatigue but it significantly increased the
prevalence of proteinuria, leukocyturia and erythrocyturia.
Citation: Abia
´
n-Vice
´
n J, Del Coso J, Gonza
´
lez-Milla
´
n C, Salinero JJ, Abia
´
n P (2012) Analysis of Dehydration and Strength in Elite Badminton Players. PLoS ONE 7(5):
e37821. doi:10.1371/journal.pone.0037821
Editor: Jonatan R. Ruiz, University of Granada, Spain
Received January 11, 2012; Accepted April 25, 2012; Published May 29, 2012
Copyright: ß 2012 Abia
´
n-Vice
´
n et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: These authors have no support or funding to report.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: jabian@ucjc.edu
Introduction
The negative effects of dehydration on endurance sports have
been widely demonstrated [1]. A loss of over 2% of body mass has
a negative effect on physical performance in a variety of aerobic
sports activities [1–3]. However, the effects of dehydration on
short-term high-intensity activities are less clear. While some
studies indicate that dehydration does not affect short-term muscle
performance [4,5] other investigations have found a detrimental
effect of dehydration on maximal force production [6] and high-
intensity cycling performance [7], especially when dehydration is
accompanied by hyperthermia. In a recent review, Judelson et al.
[8] indicate that dehydration has a greater influence the longer the
exercise lasts. However, these authors also indicate that a
reduction of 3–4% of body mass can reduce muscle strength by
2%, muscle power by 3% and muscle endurance during efforts of
between 30 and 120 seconds by 10%. Frequently, the dehydration
level attained during a sport activity depends on sweat rate,
duration and fluid intake.
The sweat rate recorded in a sport is conditioned by a series of
factors like exercise intensity, training level, heat-acclimatization,
environmental conditions, clothing or even the facility where the
sport is played (indoor or outdoor sports). Maughan et al. [9]
measured the sweat rate at different environmental temperatures
in elite soccer players. They found that at 5uC the players had a
sweat rate of 1.1 l/h, at 25uC of 1.2 l/h and at 32uC of 1.5 l/h.
Tippet et al. [10] found a sweat rate in tennis players of 2.060.5 l/
h during a tournament with an environmental temperature of
30.362.3uC. However, in indoor sports environmental conditions
can be controlled, like water vapor pressure (humidity) and
environmental temperature (dry temperature), so the sweat rate
will be mainly influenced by the intensity of effort [11]. Another
factor affecting sweat rate is the continuity of the sports
(continuous vs intermittent sports). In some intermittent sports
like soccer [12] and basketball [13] similar sweat rates have been
found (from 0.6 to 1.6 l/h) to those attained in cyclic sports like
cycling or running [14,15]. This is because in spite of there being
pauses, the moments of activity are of a higher intensity.
Badminton is a non contact racket sport which requires
jumping, changing direction, rapid arm movements and a wide
range of body postures [16]. Badminton can be considered an
intermittent individual sport, characterized by combining mo-
ments of high intensity interspersed with short periods of low
PLoS ONE | www.plosone.org 1 May 2012 | Volume 7 | Issue 5 | e37821
intensity or rest. In badminton, as in the rest of the racket sports,
the players have many opportunities to rehydrate during play due
to the intervals between points and sets [17], but does the player
start the match adequately hydrated? By measuring the specific
gravity of the urine (U
sg
) several studies have found that in sports
like athletics, volleyball, basketball or soccer, a large percentage of
players arrive at the match with high levels of dehydration before
the start of play [18–20]. Urine analysis is a method which has
been used in several studies to determine changes in fluid balance
[20,21] and to observe the response of the organism to physical
exercise [22]. Different studies have found that strenuous exercise
produces abnormalities in the players’ urine like modifications in
the pH value, hematuria or proteinuria [22–25]. However, it
should be mentioned that these abnormalities present in the
players’ urine after exercise are often asymptomatic and cause no
subsequent renal problems [26].
We have found no previous study that analyses the influence of
a competitive match on muscle performance in badminton
players. Current measuring systems permit assessment of dynamic
muscle force and power in real competitive situations with high
validity and reliability. But in spite of this there are no published
reference values for muscle strength and power, or their relation
with the dehydration attained during a badminton match. Studies
have been carried out on these kinetic parameters in other racket
sports, mainly tennis, and have found hand grip strength values
which vary between 400 and 500 N in men and between 300 and
400 N in women, depending on the characteristics of the players
studied [27,28].
The purpose of this study was to identify how a badminton
match affects elite badminton players with regard to dehydration,
liquid replacement, muscle strength and power using a jump and
hand grip tests. We also investigated sex differences in these
parameters. The analysis of these parameters may be helpful for
players, trainers and physiologists to recommend strategies for
liquid replacement during a badminton game.
Materials and Methods
Sample
Seventy players, 46 who participated in the men’s singles
matches (MS) and 24 who participated in the women’s singles
matches (WS) of the national Spanish championship voluntarily
participated in the study. At the time of the championship, all
participants were among the top 60 players in the National
Ranking in the modality of men’s singles and women’s singles
respectively. The men’s group had a mean 6 SD age of 22.764.2
yrs, body mass of 74.546 8.02 kg, height of 17868 cm, body fat
percentage of 8.461.4%, body muscle percentage of 50.261.3%
and training of 13.369.2 hours per week. The women’s group had
an age of 23.065.7 yrs, body mass of 59.4563.37 kg, height of
16562 cm, body fat percentage of 16.9 62.4%, body muscle
percentage of 46.5 62.0% and training of 16.5611.6 hours per
week. All participants were informed about the nature and the
purpose of the study, as well as the measurements which were
going to be taken. After that, participants signed a consent form to
allow the researchers to take the measurements and use their data
for scientific purposes. The study was approved by the local
Research Ethics Committee, in accordance with the latest version
of the Declaration of Helsinki [29].
Protocols
Three weeks before the Spanish Badminton Championship all
the players who were going to take part in the men’s singles and
women’s singles were informed about the purpose of the research
and were encouraged to participate, so that when they arrived at
the sports centre on the Friday (the day the competition started)
they were asked to go to the Stand which had been prepared at the
side of the multisport court. On arrival, the participants gave a
urine sample and had their descriptive variables measured. Height
was measured with a SECA personal height meter (SECA Ltd,
Germany) with an accuracy of 60.05 cm; body mass with a
60.05 kg scales (Radwag, Poland) and a record was made of the
number of hours they trained per week. The participants were
familiarized with the measuring instruments corresponding to the
maximal intensity tests (countermovement jump and hand grip
strength) and they signed the informed consent document.
It was agreed with the competition’s main referee that the
players would be told 10 minutes before being called to the court
so that once they had performed their warm up they could pass by
the Stand and have the pre-game measurements taken without
interfering with the normal course of the competition. Immedi-
ately before each match (after having performed their routine
warm up) and as soon as the game was over, the players were
weighed wearing the clothes they had worn during the game
(shorts and short sleeved shirt) and then performed two maximum
countermovement jumps (CMJ) and a hand grip strength test with
each hand (right and left). The drinks that the players took to the
court were also weighed before and after the match with a
portable scale with 61 g sensitivity (Tanita KD400, Japan) to
calculate liquid replacement. The mean dry temperature mea-
sured during the day of the tests was 2463uC (range: 22–27uC)
while relative humidity was 5066% (range: 42–58%).
In the CMJ test the subject jumped on a Quattro Jump force
platform (Kistler, Switzerland) with their hands on the waist at all
times. The angle of knee flexion during the CMJ was freely chosen
by the subject. The highest jump recorded out of two valid
attempts with a 1 min rest between them was chosen for the
analysis. A sampling frequency of 500 Hz was used for the
recording. In the hand grip strength test, the subject had to grip a
manual dynamometer (Takei Scientific Instruments Co. Japan) as
hard as possible. Two attempts were made with the elbow
extended, the arm parallel to the body and the wrist in neutral
position according to the indications of several authors [30,31].
There was 1 minute of rest between attempts and the highest value
was chosen for the analyses.
Urine samples were also collected before and after each match.
Each player was given a sterile container and gave a representative
mid-stream urine sample. The samples were collected and
analyzed fresh within an hour of collection. The measurement
was made by introducing a reactive strip (Combur TestH, Roche,
Spain) into a small portion of the urine sample so that the
components of the sample could react with the reactive agents on
the strip. Later, the strip was introduced into an automatic
reflection photometer which measured the parameters after an
incubation of 1 minute (Urisys 1100, Roche, Spain) [32]. The
strips had reactive agents for 10 variables so that after incubation a
detector measured the light reflected on each reactive area. The
variables measured in the urine were: specific gravity (U
sg
), pH,
protein, glucose and ketone body concentration, and the presence
of erythrocytes and leukocytes.
Variables
The following descriptive variables were recorded: age (years),
body mass (kg), height (cm), and hours of training per week. The
dependent variables analyzed in the matches were: body mass (kg),
percentage dehydration calculated from the difference in body
mass before and after the match and taking as the reference the
mass before the match (%), the quantity of liquid that the players
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 2 May 2012 | Volume 7 | Issue 5 | e37821
drank during the match (l/h), the duration of the match (min), the
height of the jumps calculated from the flight time (cm), mean
power during the push-off phase of the CMJ normalized for the
mass of the player (W/kg) and hand grip strength of the dominant
and non dominant hand (N). The dependent variables analyzed in
the urine samples were: specific gravity (U
sg
), pH, leukocytes
(leukocytes/
ml), nitrites (positive-negative), proteins (mg/dl), glu-
cose (mg/dl), ketone bodies (mg/dl), urobilinogen (mg/dl),
bilirubin (mg/dl), and erythrocytes (erythrocytes/
ml).
The independent variables were established as the type of match
(MS = men’s singles; WS = women’s singles) and the moment of
testing (pre = before the match; post = after the match).
Statistics
The following software programs were used: Microsoft Excel
spreadsheet (Microsoft, Spain) to store the results and the SPSS v.
17.0 program (SPSS Inc., USA) to perform the statistical
calculations using descriptive, inferential and normality statistical
tests and to calculate means, standard deviations and ranges. A
two way ANOVA (262) for repeated measures was used as the
inferential test to analyze pre-post and gender differences, the first
factor being the moment of testing (pre-post) and the second the
match modality (MS-WS). When there were significant differences
the Bonferroni post-hoc test was applied. In tests where
measurements were not taken before and after the match as in
the case of hydration, percentage of dehydration and match
duration, Student’s t test for independent samples was used to
establish the differences between the different match modalities.
The McNemar test for related proportions was used to analyze the
differences before and after each match in the dichotomic
variables which were revealed in some urine parameters. The
criterion for statistical significance was set at p,0.05.
Results
A sweat rate of 1.0260.61 l/h was recorded in the women and
1.1460.46 l/h in the men during the badminton game. The rate
of fluid intake in the WS was 1.01 60.44 l/h compared with
1.1060.55 l/h in the MS matches. The MS matches lasted on
average 7.66 minutes longer than the WS matches
(WS = 35.08611.72 min, MS = 42.74611.30; p,0.05). There
was a significant loss of mass from the beginning of the match to
the end in both the WS (Pre = 60.764.1 kg, Post = 60.564.1;
p,0.05) and the MS (Pre = 74.467.2 kg, Post = 74.167.2;
p,0.05) which represented a dehydration of 0.3260.83% in the
former and 0.37 6 0.50% in the latter.
The results obtained in the variables analyzed for the CMJ and
hand grip strength tests are shown in Figures 1 and 2. There was
an increase of 4.567.3% (p,0.05) in the height of the jumps after
the MS matches. Higher values were observed in the men’s group
than in the women’s group in the mean power of the push-off
phase and in hand grip strength both in the right and the left hand.
Considerable differences were found in the subjects’ hand grip
strength between the dominant and non dominant side (Figure 2).
There was a significant decrease in the urinary pH values in the
men’s group after the match (pre = 7.2061.08, post = 6.2861.05;
p,0.05). There was also a decrease in the women’s group
although it was not significant (pre = 7.2061.21,
post = 6.2560.87; p = 0.059). An increase was observed in the
nitrite and protein concentration after the match in both the men’s
and women’s groups (Table 1). Before the match 0.4% of the men
were positive for nitrites compared to 52.2% after the match. The
tendency in the women’s group was similar, no subjects showed
positive in this test before the start of the competition, but 58.3%
showed positive after it. Before the competition only 10.0% of the
women and 8.6% of the men had a urine protein concentration
$25 mg/dl; however, after the match these values increased to
66.7% in the women and 60.9% in the men, with 34.8% of the
men revealing values of $150 mg/dl. There was also an increase
in glucose concentration in the men at the end of the match,
17.4% of whom had values $50 mg/dl. The percentage of
subjects who had a value of erythrocytes of over 10 erythrocytes/
ml
also increased. Significant differences were not found in the
remaining variables (Table 1).
Discussion
Hydration and Fluid Replacement
The sweat rate of players in an elite competitive badminton
match was 1.0260.61 l/h in the women and 1.1460.46 l/h in the
men. The matches used for the present study were played at a
mean neutral environmental temperature of 2463uC. Badminton
is an indoor sport and contrary to what happens in outdoor sports,
environmental conditions can be controlled (mainly humidity and
dry temperature). In the case of indoor sports, sweat rates are
principally influenced by intensity of effort and the pauses in the
game [11]. The sweat rate recorded in the present study was
similar to that found by Maughan et al. [9] when they analyzed
elite soccer players at a temperature of 25uC, similar to the
temperature recorded in our study. However the sweat rate was
lower than that recorded by different authors whose studies were
performed at higher temperatures. Maughan et al. [9] recorded
1.5 l/h in soccer players at an environmental temperature of 32uC
and Tippet et al. (2011) [10] measured a sweat rate of 2.060.5 l/h
during a tennis tournament played at an environmental temper-
ature of 30.362.3uC, 6uC higher than the temperature recorded
in the present study.
The sweat rate recorded in the badminton matches was slightly
lower than that found by Hamouti et al. [18]. These authors
analyzed sweat rate in collective acyclic indoor sports like soccer,
basketball, volleyball and handball, in similar conditions to ours
(2162uC) with volleyball and handball revealing the lowest sweat
rates (1.260.3 l/h) while indoor soccer showed the highest sweat
rate with a mean of 1.860.7 l/h. Badminton, with a small court
and play characteristics which involve a multitude of jumps and
changes of direction over short distances could be most likened to
volleyball, in which similar sweat rates were found.
The value for dehydration recorded in the WS was
0.3260.83% and 0.3760.50% in MS. Twelve percent of the
players had a dehydration level higher than 1%, only one of these
had a value higher than 2% while 66% of the players revealed
values between 0–1%; and 22% presented hyperhydration, which
in no case was higher than 1%. To summarize, the hydration
habits shown by the badminton players were adequate to prevent
the 2% dehydration which can cause a decrease in sports
performance [1–3]. The rest intervals which occur during a
badminton match favor the adequate hydration of the players, as
each player has a 60 second rest when the first player reaches 11
points in each set and 120 seconds between sets. The player is free
to drink fluids during these time periods, to which must be added
the possibility of asking the referee for permission to take in fluids
in the break between points. According to Chen and Chen [33]
the mean length of time that a badminton point lasts is 8.460.2 s
with a break between points of 16.560.5 s, so the ratio between
play and rest is 1:2.
Hamouti et al. [18] found higher dehydration levels than in our
study in indoor soccer (1.260.8%) and basketball (1.160.5%)
although volleyball players had similar dehydration values
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 3 May 2012 | Volume 7 | Issue 5 | e37821
Figure 1. Countermovement jump variables. WS = Women’s singles, MS = Men’s singles, # = significant differences p,0.05 obtained
comparing men’s singles with women’s singles.
doi:10.1371/journal.pone.0037821.g001
Figure 2. Hand grip strength test variables. WS = Women’s singles, MS = Men’s singles, * = significant differences p,0.05 obtained
comparing pre and post match measurements, # = significant differences p,0.05 obtained comparing men’s singles with women’s singles, { =
significant differences p,0.05 obtained comparing hand grip strength of the right hand with the left hand.
doi:10.1371/journal.pone.0037821.g002
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 4 May 2012 | Volume 7 | Issue 5 | e37821
(0.460.6%). As mentioned before, volleyball with its play
characteristics (size of court and type of effort) would be the
indoor sport most similar to badminton, also with regard to access
to fluids and the rest intervals during play. The players did not
reach the critical value of 2% which can affect sports performance
in any of the sports analyzed by Hamouti et al. [18], which may
possibly be due to the access to fluids for hydration which is
possible in indoor acyclic sports compared with cyclic sports,
where much higher values of percentage dehydration, between 2%
and 6%, have been recorded in prolonged efforts like the
marathon [34].
Jump and Hand Grip Strength
Muscle fatigue is defined as the reduction in the maximum
capacity of the muscle to generate force [35]. However we did not
find pre-post game differences in the force generated during the
CMJ jump or during the hand grip strength test (Figures 1 and 2).
The power recorded in the jump before and after the badminton
match was not modified so these data suggest that the badminton
match did not produce muscle fatigue in either the lower or upper
limbs. These data coincide with the results obtained by Zemkova
and Hamar [36] who did not find a decrease in the height of the
CMJ nor squat jump (SJ) after a professional soccer match.
Similarly, several authors have found that certain exercises used to
produce dehydration did not cause fatigue in maximal muscle
power or strength [5,37–39]. Gutie´rrez et al. [5] found no
decreases in hand grip strength with a level of dehydration of 1.8%
neither Hoffman et al. [37] found differences in jump height in
spite of having induced a level of dehydration of 1.8%. Hayes and
Morse [39] found no decrease in jump height in a protocol of 5
efforts designed to generate progressive dehydration by running in
a hot climate ( ,48uC). On the contrary, the men’s group in our
study raised the height recorded in the jump with an increase of
4.567.3% after the match. As happened to the men in the present
study, Viitasalo et al. [38] found an increase in jump height of
7.1% in subjects with a level of dehydration of 2.5%, and
concluded that dehydration generated with a diuretic method did
not produce a decrease in neuromuscular performance. Equally
we can state that a badminton match, which is characterized by
high intensity actions during brief time periods, and a match
duration between 35 and 45 minutes [33] did not produce muscle
fatigue in the lower limbs nor in the force generated in a hand grip
test.
The men showed higher values than the women in all the CMJ
parameters analyzed (height, and mean power in the push-off
phase) and in the hand grip strength test (Figure 1). The men
attained 27.7% more jump height than the women in the post
match recording; 17.2% more power in the push-off phase of the
jump and 37.1% more hand grip strength after the match. Abian-
Vice´n et al. [40] found similar values to the present study in 291
physically active men and 92 physically active women, where the
men recorded 27.8% more height in the CMJ than the women
and 20.7% more peak power in the jump. These values suggest
that the specific badminton training has not modified the gender
differences presented in physically active subjects who have not
had specific training. It is worthy of note that power was
normalized with regard to the mass of the subjects which reduced
the percentage difference with respect to the height of the jumps
(from 27 to 17%) but did not eliminate the gender difference.
The height of the countermovement jump was greater than that
found by different authors studying physically active subjects who
did not practice sports professionally [40,41], and it is similar to
that obtained by professional basketball players [42] and slightly
lower than that found by Riggs and Shephard [43] in professional
beach volleyball players. Given that to date no research has
provided such data on badminton players, the values shown in this
study related to the CMJ and hand grip strength can serve as a
reference for elite male and female badminton players at the most
important moment of the season for most of them, which is the
National Spanish Championship.
Table 1. Percentage of cases showing values presented for each of the urinary parameters analyzed before (pre) and after (post)
the match.
WS MS
PRE (%) POST (%) PRE (%) POST (%)
25 20.0 33.3 4.3 39.1
Leukocytes
(leukocytes/ml)
$100 20.0 16.7 0.0 4.3
% accumulated 40.0 50.0 4.3 43.5*
Nitrites Positive 0.0 58.3* 0.4 52.2*
25 10.0 16.7 8.6 17.4
Proteins
(mg/dl)
75 0.0 33.3 0.0 8.7
$150 0.0 16.7 0.0 34.8
% accumulated 10.0 66.7* 8.6 60.9*
Glucose
(mg/dl)
$
50 0.0 0.0 0.0 17.4*
Ketone bodies (mg/dl)
$
5 0.0 0.0 8.6 17.4
UBG (mg/dl)
$
1 10.0 25.0 30.4 39.1
Bilirubin (mg/dl)
$
1 10.0 33.3 30.4 39.1
Erythrocytes
(Erythrocytes/
ml)
$
10 20.0 50.0* 4.3 21.7*
(WS = Women’s singles, MS = Men’s singles, * = significant differences p,0.05 obtained comparing pre and post match measurements).
doi:10.1371/journal.pone.0037821.t001
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 5 May 2012 | Volume 7 | Issue 5 | e37821
Maximum force production generated in the hand grip test is
one of the characteristics which have been studied the most in
racket sports like tennis and squash [27,28], possibly due to its
importance for handling the racket. However, there are no
reference data for badminton players, whose values are higher
than those recorded by Alkurdi and Dweiri [44] in 20 German
male students (dominant = 300.9685.1 N, non domi-
nant = 290.3669.2 N) using the same methodology as in the
present study, and lower than those recorded by Ducher et al. [45]
in 52 tennis players (dominant = 602.76155.7 N, non domi-
nant = 521.16128.5 N). These differences may possibly be due to
the fact that badminton players use a racket which weighs 3 to 4
times less than a tennis racket (badminton ,100 g; tennis ,350 g)
so that the grip strength needed by the badminton player to handle
the racket will be less than that of the tennis player. The
differences found between the dominant and non dominant side in
both the men’s and women’s group are worthy of mention
(8.069.5% in the pre test), as earlier studies have shown how these
differences between both arms are greater in players of racket
sports than in the sedentary population [46]. The differences
found in the present study are similar to those presented by
Mahoney and Sharp [47] who found an asymmetry between the
dominant and non dominant side of 13% in hand grip strength in
squash players, or the values obtained by Ducher et al. [45] who
recorded a difference of 13.5% in 52 tennis players who had
practiced this sport for an average of 16.266.1 years. Ducher et al.
[45] established a significant Pearson correlation between hand
grip strength and the bone mineral content of the forearm
(r = 0.81) and the bone mineral density of the forearm (r = 0.67),
which indicates that the badminton players, like the tennis players,
may possibly have greater bone mineral development in the
dominant versus the non dominant side.
Urine Analysis
The specific gravity of urine is often used to measure the state of
hydration of athletes before exercise, being a simple, low cost and
non invasive method [19–21,48]. It is estimated that ,1.020 is the
limit for considering that an athlete is correctly hydrated
[19,49,50], although this value may be higher in athletes with a
large muscle mass [48]. In a recent study Armstrong et al. [49]
corrected these values by differentiating between the reference
values for the first urine in the morning (U
sg
euhydrated = 1022–
1023) and 24 hours after daily activity (U
sg
euhydrated = 1015–
1017). In the present study we found that 90.9% of the players
arrived with values lower than 1.020. After the competition, the
specific gravity of the urine was not modified, because the players
did not dehydrate (dehydration: women = 0.3260.83%;
men = 0.3760.50%) and also because U
sg
is a marker which
involves some delay in revealing dehydration [50].
After intense exercise, urine becomes more acid and there is an
increase in ammonia excretion which leads to a decrease in pH.
This urine acidity occurs 10 minutes after ceasing exercise and it is
maintained for up to 50–90 minutes afterwards [51]. The
badminton match caused a decrease in the pH of the urine which
was significant in the men’s group (pre = 7.2061.21;
post = 6.2560.87, p,0.05) and tended to be significant in the
women’s group (pre = 7.2061.08; post = 6.2861.05, p = 0.06).
Changes in urinary pH are mainly determined by blood pH and
thus urinary pH may be an indicator of how extreme the blood pH
modification has been [52]. Badminton is a sport which requires
multiple efforts with a short duration but high intensity [33] which
favor the accumulation of lactic acid [16].
Different studies have analyzed how intense exercise influences
urinary pH [23,24,52]. Some of these studies show different
possibilities for countering or delaying the acidosis caused by
exercise, like taking bicarbonate [24] or consuming an alkaline diet
[52] before beginning exercise, with less than conclusive results
with regard to improving performance. Rios-Enriquez et al. [52]
found that no improvement was evident in performance in an
anaerobic high intensity test after consuming an alkaline diet, but
that there was a decrease in urinary acidity after exercise. Carr
et al. [24] also found an increase in urinary pH after exercise due
to taking 0.3 g/kg of bicarbonate. The improvement in perfor-
mance in a 2000 m rowing test was not significant when only
bicarbonate was used, but it was significant when it was combined
with 6 mg/kg of caffeine. McInnis et al. [23], analyzed the
influence of 4 different types of exercise on urinary pH (36
Wingate of 60 seconds, 36400 m sprinting, cycling at 90% of the
aerobic threshold and running at 90% of the aerobic threshold).
These authors found no significant differences, but did however
see a tendency to a more marked decrease in pH in the higher
intensity efforts (Wingate and sprint). In the present study, players
had to perform a great number of repeated maximum intensity
efforts during the matches (,40 minutes) which produced higher
urine acidity.
The badminton match also produced different signs of
imbalance in the various urinary parameters which were analyzed:
leukocyturia, an increase in the presence of nitrites, proteinuria
and an increase in the presence of erythrocytes and glucosuria in
the men’s group (Table 1). Numerous studies state that high
intensity exercise causes the appearance of hematuria and
proteinuria, due to an alteration in renal function [23]. Poortmans
[53] suggests that post exercise proteinuria arises as a result of the
increase in glomerular permeability as, if the exercise is prolonged,
red blood cells may be lost via the urine. The decreased blood flow
to the kidneys is proportional to the intensity of the exercise, with a
30% reduction for exercise at 50% of VO
2
max and a 75%
reduction with exercise at 65% of VO
2
max [54]. The drop in
blood pressure causes a decrease in blood flow to the kidneys and
an increase in the passing of red blood cells and proteins into the
urine causing hematuria and proteinuria. The proteinuria and
hematuria recorded after the badminton match are a consequence
of performing high intensity exercise [23] and give an idea of the
high intensity involved.
On the competition day, 60% of the players analyzed revealed
values higher than 25 mg of protein per dl of urine proteins.
Similar responses in urinary protein concentration have been
recorded before in other types of exercise. Gur et al. [25] found
that 73.3% of runners revealed proteinuria after completing a half
marathon while Boileau et al. [22] found proteinuria in 30% of
383 runners after completing a marathon. McInnis et al. [23]
found an increase in protein concentration after 3 series of 400 m
at maximum intensity, however they did not find changes in
urinary protein concentration when exercise was performed at a
lower intensity than the aerobic threshold, which situates
badminton matches in the category of high intensity anaerobic
activities. The increase in the players’ urinary erythrocyte
concentration may be due to the fact that prolonged and
exhausting effort can cause an increase in the destruction of the
red blood cells as a consequence of the compression of the
capillaries by the muscle contractions, the increase of the speed of
blood flow as well as the impacts suffered by the feet when
absorbing the shocks of the constant jumps and changes of
direction involved in the matches [26].
Conclusions
The badminton players’ sweat rate was 1.02 l/h in the women
and 1.14 l/h in the men, values similar to those recorded in other
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 6 May 2012 | Volume 7 | Issue 5 | e37821
acyclic indoor sports played at a neutral environmental temper-
ature. The badminton players came to the match with an
adequate hydration level and maintained suitable hydration
during the matches by an adequate fluid intake regime. These
patterns prevented a level of dehydration which could have
negatively influenced their performance. The badminton match
did not produce muscle fatigue in the lower or upper limbs as
jump height and hand grip strength were not modified. There was
an evident asymmetry in hand grip strength in favor of the
dominant side. No gender differences were found in the hydration
parameters, however, the duration of the men’s matches was
greater and they showed higher levels of power in their lower limbs
and greater strength in their upper limbs. After the match, the
urine analyses showed proteinuria, an increase in the presence of
nitrites and erythrocytes and leukocyturia mainly produced by the
high intensity of the game. Similar urinary anomalies have been
observed in sports of longer duration like the half marathon or
marathon.
Author Contributions
Conceived and designed the experiments: JAV JDC PAV. Performed the
experiments: JAV JDC JJS CGM. Analyzed the data: JAV JJS CGM PAV.
Contributed reagents/materials/analysis tools: JAV JDC JJS CGM. Wrote
the paper: JAV JDC JJS CGM PAV.
References
1. Sawka MN, Young AJ (2006) Physiological systems and their responses to
conditions of heat and cold In: Tipton CMS, M. N.; Tate, C A, Terjung R L,
eds. ACSM’s a dvanced exercis e physiology. Baltimore, MD: Lippincott
Williams & Wilkins. pp 535–563.
2. Baker L B, Dougherty KA, Chow M, Kenney WL (2007) Progressive
dehydration causes a progressive decline in basketball skill performance. Med
Sci Sports Exerc 39: 1114–1123.
3. Dougherty KA, Baker LB, Chow M, Kenney WL (2006) Two percent
dehydration impairs and six percent carbohydrate drink improves boys
basketball skills. Med Sci Sports Exerc 38: 1650–1658.
4. Watson G, Judelson DA, Armstrong LE, Yeargin SW, Casa DJ, et al. (2005)
Influence of diuretic-induced dehydration on competitive sprint and power
performance. Med Sci Sports Exerc 37: 1168–1174.
5. Gutierrez A, Mesa JL, Ruiz JR, Chirosa LJ, Castillo MJ (2003) Sauna-induced
rapid weigh t loss decreases explosive power in women but not in men. Int J Sports
Med 24: 518–522.
6. Coso JD, Estevez E, Baquero RA, Mora-Rodriguez R (2008) Anaerobic
performance when rehydrating with water or commercially available sports
drinks during prolonged exercise in the heat. Appl Physiol Nutr Metab 33:
290–298.
7. Walsh RM, Noakes TD, Hawley JA, Dennis SC (1994) Impaired high-intensity
cycling performance time at low levels of dehydration. Int J Sports Med 15:
392–398.
8. Judelson DA, Maresh CM, Anderson JM, A rmstrong LE, Casa DJ, et al. (2007)
Hydration and muscular performance: does fluid balance affect strength, power
and high-intensity endurance? Sports Med 37: 907–921.
9. Maughan RJ, Shirreffs SM, Merson SJ, Horswill CA (2005) Fluid and electrolyte
balance in elite male football (soccer) players training in a cool environment.
J Sports Sci 23: 73–79.
10. Tippet ML, Stofan JR, Lacambra M, Horswill CA (2011) Core temperature and
sweat responses in professional women’s tennis players during tournament play
in the heat. J Athl Train 46: 55–60.
11. Buono MJ, Lee NV, Miller PW (2010) The relationship between exercise
intensity and the sweat lactate excretion rate. J Physiol Sci 60: 103–107.
12. Maughan RJ, Shirreffs SM (2010) Development of hydration strategies to
optimize performance for athletes in high-intensity sports and in sports with
repeated intense efforts. Scand J Med Sci Sports 20 Suppl 2: 59–69.
13. Broad EM, Burke LM, Cox GR, Heeley P, Riley M (1996) Body weight changes
and voluntary fluid intakes during training and competition sessions in team
sports. Int J Sport Nutr 6: 307–320.
14. Noakes TD, Adams BA, Myburgh KH, Greeff C, Lotz T, et al. (1988) The
danger of an inadequate water intake during prolonged exercise. A novel
concept re-visited. Eur J Appl Physiol Occup Physiol 57: 210–219.
15. S hi X, Gisolfi CV (1998) Fluid and car bohydrate r eplacement dur ing
intermittent exercise. Sports Med 25: 157–172.
16. Cabello Manrique D, Gonzalez-Badillo JJ (2003) Analysis of the characteristics
of competitive badminton. Br J Sports Med 37: 62–66.
17. Lees A (2003) Science and the major racket sports: a review. J Sports Sci 21:
707–732.
18. Hamouti N, Del Coso J, Estevez E, Mora-Rodriguez R (2010) Dehydration and
sodium deficit during indoor practice in elite European male team players.
European Journal of Sports Science 10: 329–336.
19. Silva RP, Mu¨ndel T, Altoe´ JL, Saldanha MR, Ferreira FG, et al. (2010)
Preexercise urine specific gravity and fluid intake during one-hour running in a
thermoneutral environment - a randomized cross - over study. Journal of Sports
Science and Medicine 9: 464–471.
20. Finn JP, Wood RJ (2004) Incidence of pre-game dehydration in athletes
competing at an international event in dry tropical conditions. Nutr diet 61:
221–225.
21. Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, et al. (2000)
National athletic trainers’ association position statement: fluid replacement for
athletes. J Athl Train 35: 212–224.
22. Boileau M, Fuchs E, Barry JM, Hodges CV (1980) Stress hematuria: athletic
pseudonephritis in marathoners. Urology 15: 471–474.
23. McInnis MD, Newhouse IJ, von Duvillard SP, Thayer R (1998) The effect of
exercise intensity on hematuria in healthy male runners. Eur J Appl Physiol
Occup Physiol 79: 99–105.
24. Carr AJ, Gore CJ, Dawson B (2011) Induced alkalosis and caffeine
supplementation: effects on 2,000-m rowing performance. Int J Sport Nutr
Exerc Metab 21: 357–364.
25. Gur H, Kucukoglu S, Surmen E, Muftuoglu A (1994) Effects of age, training
background and duration of running on abnormal urinary findings after a half-
marathon race. Br J Sports Med 28: 61–62.
26. Kane SF, Cohen MI (2009) Evaluation of the asymptomatic athlete with hepatic
and urinalysis abnormalities. Curr Sports Med Rep 8: 77–84.
27. Sharp NC (1998) Physiological demands and fitness for squash. In: Lees A,
Maynard I, Hughes M, Reilly T, eds. Science and Racket Sports II. London: E
& FN Spon. pp 52–55.
28. Kramer AM, Knudson DV (1992) Grip strength and fatigue in junior college
tennis players. Percept Mot Skills 75: 363–366.
29. World Medical Association (2002) Declaration of Helsinki: ethical principles for
medical research involving human subjects. J Postgrad Med 48: 206–208.
30. Segura-Orti E, Martinez-Olmos FJ (2011) Test-retest reliability and minimal
detectable change scores for sit-to-stand-to-sit tests, the six-minute walk test, the
one-leg heel-rise test, and handgrip strength in people undergoing hemodialysis.
Phys Ther 91: 1244–1252.
31. Espana-Romero V, Ortega FB, Vicente-Rodriguez G, Artero EG, Rey JP, et al.
(2010) Elbow position affects handgrip strength in adolescents: validity and
reliability of Jamar, DynEx, and TKK dynamometers. J Strength Cond Res 24:
272–277.
32. Penders JF, Fiers T, Delanghe JR (2002) Quantitative evaluation of urinalysis
test strips. Clin Chem 48: 2236–2241.
33. Chen HL, Chen TC (2008) Temporal structure comparison of the new and
conventional scoring systems for men’s badminton singles in Taiwan. Journal of
Exercise Science & fitness 6: 34–43.
34. Passe D, Horn M, Stofan J, Horswill C, Murray R (2007) Voluntary dehydration
in runners despite favorable conditions for fluid intake. Int J Sport Nutr Exerc
Metab 17: 284–295.
35. Gandevia SC (2001) Spinal and supraspinal factors in human muscle fatigue.
Physiol Rev 81: 1725–1789.
36. Zemkova E, Hamar D (2009) The effect of soccer match induced fatigue on
neuromuscular performance. Kinesiology 41: 195–202.
37. Hoffman JR, Stavsky H, Falk B (1995) The effect of water restriction on
anaerobic power and vertical jumping height in basketball players. Int J Sports
Med 16: 214–218.
38. Viitasalo JT, Kyrolainen H, Bosco C, Alen M (1987) Effects of rapid weight
reduction on force production and vertical jumping height. Int J Sports Med 8:
281–285.
39. Hayes LD, Morse CI (2010) The effects of progressive dehydration on strength
and power: is there a dose response? Eur J Appl Physiol 108: 701–707.
40. Abian J, Alegre LM, Lara AJ, Rubio JA, Aguado X (2008) Landing differences
between men and women in a maximal vertical jump aptitude test. J Sports Med
Phys Fitness 48: 305–310.
41. Lara AJ, Abian J, Alegre LM, Jimenez L, Aguado X (2006) Assessment of power
output in jump tests for applicants to a sports sciences degree. J Sports Med Phys
Fitness 46: 419–424.
42. Apostolidis N, Nassis GP, Bolatoglou T, Geladas ND (2004) Physiological and
technical characteristics of elite young basketball players. J Sports Med Phys
Fitness 44: 157–163.
43. Riggs MP, Sheppard JM (2009) The relative importance of strength and power
qualities to vertical jump height of elite beach volleyball players during the
counter-movement and squat jump. Journal of Human Sport and Exercise 4:
221–236.
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 7 May 2012 | Volume 7 | Issue 5 | e37821
44. Alkurdi ZD, Dweiri YM (2010) A biomechanical assessment of isometric
handgrip force and fatigue at different anatomical positions. J Appl Biomech 26:
123–133.
45. Ducher G, Jaffre C, Arlettaz A, Benhamou CL, Courteix D (2005) Effects of
long-term tennis playing on the muscle-bone relationship in the dominant and
nondominant forearms. Can J Appl Physiol 30: 3–17.
46. Kannus P, Haapasalo H, Sankelo M, Sievanen H, Pasanen M, et al. (1995)
Effect of starting age of physical activity on bone mass in the dominant arm of
tennis and squash players. Ann Intern Med 123: 27–31.
47. Mahoney CA, Sharp NC (1995) The physiolog ical profile of elite junior squash
players. In: Reilly T, Hughes M, Lees A, eds. Science an Racket Sports. London:
E & FN Spon.
48. Hamouti N, Del Coso J, Avila A, Mora-Rodriguez R (2010) Effects of athletes’
muscle mass on urinary markers of hydration status. Eur J Appl Physiol 109:
213–219.
49. Armstrong LE, Pumerantz AC, Fiala KA, Roti MW, Kavouras SA, et al. (2010)
Human hydration indices: acute and longitudinal reference values. Int J Sport
Nutr Exerc Metab 20: 145–153.
50. Popowski LA, Oppliger RA, Patrick Lambert G, Johnson RF, Kim Johnson A,
et al. (2001) Blood and urinary measures of hydration status during progressive
acute dehydration. Med Sci Sports Exerc 33: 747–753.
51. Wilson DW, Long WL, Thompson HC, Thurlow S (1925) Changes in the
composition of the urine after muscular exercise. The Journal of Biological
Chemistry 65: 755–771.
52. Rios-Enriquez O, Guerra-Hernandez E, Feriche B (2010) Efectos de la alcalosis
metabo´lica inducida por la dieta en el rendimiento anero´bico de alta intensidad.
Nutricio´n Hospitalaria 25: 768–773.
53. Poortmans JR (1977) Exercise and renal function. Exerc Sport Sci Rev 5:
255–294.
54. Poortmans JR (1984) Exercise and renal function. Sports Med 1: 125–153.
Dehydration and Strength in Badminton
PLoS ONE | www.plosone.org 8 May 2012 | Volume 7 | Issue 5 | e37821
