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Validity of Hydration Non-Invasive Indices during the Weightcutting and Official Weigh-In for Olympic Combat Sports


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In Olympic combat sports, weight cutting is a common practice aimed to take advantage of competing in weight divisions below the athlete's normal weight. Fluid and food restriction in combination with dehydration (sauna and/or exercise induced profuse sweating) are common weight cut methods. However, the resultant hypohydration could adversely affect health and performance outcomes. The aim of this study is to determine which of the routinely used non-invasive measures of dehydration best track urine osmolality, the gold standard non-invasive test. Immediately prior to the official weigh-in of three National Championships, the hydration status of 345 athletes of Olympic combat sports (i.e., taekwondo, boxing and wrestling) was determined using five separate techniques: i) urine osmolality (UOSM), ii) urine specific gravity (USG), iii) urine color (UCOL), iv) bioelectrical impedance analysis (BIA), and v) thirst perception scale (TPS). All techniques were correlated with UOSM divided into three groups: euhydrated (G1; UOSM 250-700 mOsm·kg H2O-1), dehydrated (G2; UOSM 701-1080 mOsm·kg H2O-1), and severely dehydrated (G3; UOSM 1081-1500 mOsm·kg H2O-1). We found a positive high correlation between the UOSM and USG (r = 0.89: p = 0.000), although this relationship lost strength as dehydration increased (G1 r = 0.92; G2 r = 0.73; and G3 r = 0.65; p = 0.000). UCOL showed a moderate although significant correlation when considering the whole sample (r = 0.743: p = 0.000) and G1 (r = 0.702: p = 0.000) but low correlation for the two dehydrated groups (r = 0.498-0.398). TPS and BIA showed very low correlation sizes for all groups assessed. In a wide range of pre-competitive hydration status (UOSM 250-1500 mOsm·kg H2O-1), USG is highly associated with UOSM while being a more affordable and easy to use technique. UCOL is a suitable tool when USG is not available. However, BIA or TPS are not sensitive enough to detect hypohydration at official weight-in before an Olympic combat championship.
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Validity of Hydration Non-Invasive Indices during the
Weightcutting and Official Weigh-In for Olympic Combat
´n E. Ferna
, Alberto Martı
, Jose
, Ricardo Mora
, Jesu
´s G. Pallare
, Ernesto De la Cruz-Sa
, Ricardo Mora-Rodriguez
1Exercise Physiology Laboratory, University of Castilla-La Mancha, Toledo, Spain, 2Department of Physical Activity and Sport, University of Murcia, Murcia, Spain
In Olympic combat sports, weight cutting is a common practice aimed to take advantage of competing in
weight divisions below the athlete’s normal weight. Fluid and food restriction in combination with dehydration (sauna and/
or exercise induced profuse sweating) are common weight cut methods. However, the resultant hypohydration could
adversely affect health and performance outcomes.
The aim of this study is to determine which of the routinely used non-invasive measures of dehydration best track
urine osmolality, the gold standard non-invasive test.
Immediately prior to the official weigh-in of three National Championships, the hydration status of 345 athletes of
Olympic combat sports (i.e., taekwondo, boxing and wrestling) was determined using five separate techniques: i) urine
osmolality (U
), ii) urine specific gravity (U
), iii) urine color (U
), iv) bioelectrical impedance analysis (BIA), and v) thirst
perception scale (TPS). All techniques were correlated with U
divided into three groups: euhydrated (G
700 mOsm?kg H
), dehydrated (G
701–1080 mOsm?kg H
), and severely dehydrated (G
1500 mOsm?kg H
We found a positive high correlation between the U
and U
(r = 0.89: p = 0.000), although this relationship lost
strength as dehydration increased (G
r = 0.92; G
r = 0.73; and G
r = 0.65; p = 0.000). U
showed a moderate although
significant correlation when considering the whole sample (r = 0.743: p = 0.000) and G
(r = 0.702: p = 0.000) but low
correlation for the two dehydrated groups (r =0.498–0.398). TPS and BIA showed very low correlation sizes for all groups
In a wide range of pre-competitive hydration status (U
250–1500 mOsm?kg H
), U
is highly associated
with U
while being a more affordable and easy to use technique. U
is a suitable tool when U
is not available.
However, BIA or TPS are not sensitive enough to detect hypohydration at official weight-in before an Olympic combat
Citation: Ferna
´as VE, Martı
´n JM, Mora
´n-Navarro R, Pallare
´s JG, et al. (2014) Validity of Hydration Non-Invasive Indices during
the Weightcutting and Official Weigh-In for Olympic Combat Sports. PLoS ONE 9(4): e95336. doi:10.1371/journal.pone.0095336
Editor: Reury F.P. Bacurau, University of Sao Paulo, Brazil
Received December 11, 2013; Accepted March 26, 2014; Published April 16, 2014
Copyright: ß2014 Ferna
´as 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: This study was supported by grants from the High-Performance Sports Center Infanta Cristina (General Directorate of Sports, Government of Murcia).
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail:
Severe dehydration has physiological consequences negatively
affecting health and athletic performance. Body water losses
exceeding 2% of body weight reduce physical work capacity and
exercise performance [1–3] and higher dehydration levels (i.e..4–
5%) has been reported to increase heat-stroke risk [1,4]. These
adverse effects include impaired glycogen use [9], increases in core
temperature inducing central nervous system fatigue [10,11],
cardiovascular strain [12,13] and loss of efficacy of the metabolic
acid buffer system [14]. All these effects could compromise health
and physical performance in military personnel, firemen, athletes
training and competing in hot environments, or those involved in
Olympic weight-class sports (e.g. wrestling, boxing, judo, taek-
wondo and weightlifting). In these sports weight loss throughout
dehydration is a very common strategy prior to competition [15].
Weight loss by dehydration has been shown to affect boxing and
wrestling performance [5,6]. If that weight loss is quickly
recovered the effects on performance are not evident [7,8]. Many
techniques are available to assess body water deficit, however it is
not clear which it is best to use in a pre-competition setting.
Ideally, this should be a non-invasive index, as well as being fast,
accurate, inexpensive and easy-to-use.
Out of the available techniques to measure hydration status,
blood osmolality is the gold standard [16–18]. However, the
measurement of blood osmolality requires an invasive technique,
PLOS ONE | 1 April 2014 | Volume 9 | Issue 4 | e95336
costly measurement apparatus and qualified personnel to handle
blood. All these conditions are rarely available to scientists and
coaches at the field. Urine analysis of hydration status has been
recommended as an alternative measurement because it involves a
noninvasive evaluation of body fluid [19]. The main criticism of
the use urine as an index of dehydration is that urine does not
respond as fast or as accurately as blood to body fluid deficit [16].
However, we have recently found that urine readily tracks blood
responses during progressive dehydration induced by exercise
[20,21]. Urine can be analyzed for color, density, osmolality or its
constituents resulting in a wide range of hydration indexes.
Nonetheless, not all indexes are adequate, accurate or practical,
and some are costly and require technical expertise [22].
A non-invasive surrogate of blood osmolality is urine osmolality
) considered the most valid measurement of hydration status
through urine [16,23]. However, similarly to blood osmolality it
requires expensive biochemical analysis. Urine specific gravity
) assessment requires a simpler apparatus (i.e., refractrom-
eter). Some authors have found that U
[20,21,24]and urine
color (U
) [22,25] are highly correlated to urine osmolality
). Armstrong and co-workers, found acceptable validity of
and color analysis in different populations at moderate
dehydration levels [17]. However, the agreement between these
urine indexes after severe dehydration in weight class sports [15],
has not been reported.
Finally, there are non-invasive indexes that do not entail urine
collection and analysis. Bioelectrical impedance analysis (BIA;
[26–29]) and thirst perception scale (TPS; [30–33]) have been
proposed as simpler indexes of body fluid deficit. Despite all these
studies, to our knowledge, there is insufficient evidence to decide
about the suitability of these indexes to readily detect whole body
dehydration. Furthermore, these indexes have not been evaluated
in a large population of athletes undergoing different degrees of
dehydration. We believe that a good test for BIA and TPS will be
to assess its agreement with U
during the weight cutting in
Olympic combat sports.
Therefore, the purpose of this study was to compare several
non-invasive indexes of hydration in a large number of Olympic
combat sport athletes undergoing different degrees of weight loss
by dehydration before a real competition. Our intention is to
obtain a wide range of hypohydration levels to fully evaluate the
detection power of all indexes in comparison to U
hypothesized that techniques involving urine analysis may have
high levels of agreement while other estimations (i.e. BIA and TPS)
will not.
Two hundred and forty-four male (age 22.864.1 yr, body mass
74.1615.1 kg, height 176.166.7 cm) and one hundred one female
(age 22.764.5 yr, body mass 57.168.9 kg, height 164.967.2 cm)
high performance athletes of three different Olympic combat
sports volunteered to participate in this study: wrestling (n = 157),
taekwondo (n = 152) and boxing (n = 36). All participants had at
least 4years of training and competition experience, and all of
them made the weight in the official weigh-in of their respective
national championship during the experimental phase of this
study. The subjects and coaches were informed in detail about the
experimental procedures and the possible risks and benefits of the
project. The study, which complied with the Declaration of
Helsinki, was approved by the Bioethics Commission of the
University of Murcia, and written informed consent was obtained
from athletes prior to participation.
Study design and experimental protocol
Athletes’ hydration status was evaluated through 5 different
techniques (i.e., U
, TPS and BIA) between 60
and 5 minutes before the official weigh-in of their respective
National Championship. No instructions were given to athletes or
their coaches about their weight control management. Participants
filled out a nutritional questionnaire and twelve of them were
excluded from the study for being ingesting vitamins, nutritional
supplements or prescription drugs prone to alter urine color,
amount or composition [25]. Women were tested out of the
proliferative phase of their menstruation.
At arrival to the official weigh-in facilities, a 10 ml mid flow
urine sample was obtained from each athlete. After the recipient
with the urine sample was handed over and codified, subjects filled
out the thirst perception scale, and their body impedance was
determined using a Bio-impedance analyzer. Urine specimens
were immediately analyzed in duplicate for urine osmolality
), urine specific gravity (U
), and urine color (U
) by the
same experienced investigator. The final value for each assessment
was the average of the two trials.
Urine osmolality. U
is the measure of the total urine
solute content. As has been repeatedly reported [16,23], we
considered this assessment as our gold standard measurement to
determine the athletes’ hydration status. Athletes urine specimens
(20 mL) were immediately analyzed in duplicate by freezing point
depression osmometry (Model 3250, Advanced Instruments,
Urine specific gravity. U
is the analysis of urine density
compared to double distilled water (density = 1.000). After
apparatus calibration and thorough mixing of the urine specimen,
a few drops were placed on the refractometer (URC-NE, Atago,
Japan) visor and U
was determined.
Urine color. U
is determined by the amount of
urochrome present in the urine specimen. When large volumes
of urine are excreted, the urine is dilute and pale. Conversely,
when small volumes of urine are excreted, the urine is
concentrated and dark [23]. U
was determined as described
by Arsmstrong et al., [17,18,22,23,25]. Briefly, an 8 number scale
ranging from very pale yellow (number 1) to brownish green
(number 8), was used. U
was determined in duplicate by
holding each specimen container next to a validated color scale in
a well-lit room.
Bioelectrical impedance analysis. BIA has the potential to
assess changes in hydration status and has been previously used
and validated in combat sports athletes [29]. Athletes BIA was
determined using an 8-contact electrode segmental and mono-
frequency body composition analyzer (Tanita BC-418, Tanita
Corp., Tokyo, Japan) while they were barefoot, wearing shorts and
a sports-top for females.
Thirst perception scale (TPS). Thirst perception is physi-
ologically related to the hydration status of an individual since it is
mediated by fluid-regulating hormones urging the ‘‘need to drink’’
[31]. Thirst perception was assessed using a Liker scale[32,34] that
ranged perceived thirst from 1 (‘‘not thirsty at all’’) to 9 (‘‘very,
very thirsty’’).
Statistical analysis
Descriptive values were provided for all the outcome variables.
Engagement scores were non-normally distributed for all mea-
sures, as assessed by Shapiro-Wilk’s test (p,0.05). A Spearman’s
rank-order correlation was run to assess the relationship between
and the rest of the hydration status markers (U
TPS and BIA). The size of the correlation was evaluated as
follows; r,0.7 low; 0.7#r,0.9 moderate; and $0.9 high [35].
Validity of Hydration Status Markers
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Subjects were stratified according to their hydration status using
values. A value of 700 mOsm?kg H
marks the limits
between a correct hydration status and dehydration [1]. Thus,
three intervals of equal amplitude (according to measurement
units) were established according to the following cutoffs: from 250
to 700 mOsm?kg H
(euhydrated - G
), from 701 to
1.080 mOsm?kg H
(dehydrated - G
) and from 1.081 to
1.500 mOsm?kg H
(severely dehydrated - G
). Also, a
Kruskal-Wallis test was performed between groups. Pairwise
comparisons were performed using Dunn’s [36] procedure with
a Bonferroni correction for multiple comparisons.
Hydration status indexes were not different between males and
females (U-Mann Whitney Wilcoxon test; p.0.05) or between
sports (wrestling, taekwondo and boxing; Kruskal-Wallis test;
p.0.05) and thus results are reported with all athletes as a group.
A high linear and positive correlation was detected between U
and U
in the whole sample (r = 0.89; p = 0.000; n = 345).
However, the correlation became lower as the dehydration status
increased (G
r = 0.92; p = 0.000; G
r = 0.73; p = 0.000 and G
r = 0.65; p = 0.000; Figure 1A).
The relationship between the U
and other hydration
status markers was weak. U
showed a moderate although
significant correlation when considering the whole sample
(r = 0.743; p = 0.000) or the euhydrated group (G1: r = 0.702;
p = 0.000). However, the correlation was low for the two
dehydrated groups (G2: r = 0.498; p = 0.002; G3: r = 0.398;
p = 0.004) (Figure 1B). TPS showed a significant but low
correlation with the U
in the whole sample and for G3 group
(r,0.315 and r = 0.298, respectively; p,0.05) (Figure 1C). No
significant correlation (p.0.05) was detected between the BIA
assessments and U
in any group (Figure 1D).
Finally, a complementary Kruskal-Wallis analysis according to
the athletes’ dehydration status (euhydrated – G1, dehydrated –
G2; and severely dehydrated –G3) reveals significant differences
(p,0.05) between the 3 groups for the U
and U
Nevertheless, the TPS cannot differ (p,0.05) between the first two
groups (G1 and G2), and BIA do not distinguish (p,0.05) between
any of the 3 groups (G1, G2 and G3) (Figure 2).
Figure 1. Correlation between U
and U
(A), Urine color (B), Thirst perception scale (C) and Bioelectrical impedance analysis (D)
in the whole sample and in each group. G1: U
250–700 mOsm?kg H
; G2: U
701–1.080 mOsm?kg H
; G3. U
1.500 mOsm?kg H
Validity of Hydration Status Markers
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Validity of Hydration Status Markers
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The current study compares different indexes of hydration
status to urine osmolality (U
) as the gold standard non-invasive
index [16,23]. This comparison took place in a large sample of
Olympic combat sports athletes (i.e. 345 athletes) during the
official weigh-in of a real competition. While rapid reduction in
body weight before competition is the easier non-invasive index of
weight cutting thru dehydration it requires knowing what the
‘‘normal’’ weight of the athlete is. Referees and medical personnel
at the competition arena do not have this information and thus
require another index that is accurate, fast and non-invasive. Our
aim was to determine which of the available non-invasive indexes
; BIA and TPS) showed the better combination of
sensibility to detect hypohydration, with affordability and simplic-
ity in its use. This may prove useful to sport’s governing bodies
which are interested in preventing rapid weight loss during
competition. Coaches and trainers can benefit too from easily
assessing the degree of hypohydration in their combat athletes. We
believe that fast and accurate identification of hypohydration is the
first step into the prevention of weight cutting unhealthy practices.
While a similar question has been addressed in previous studies
[14,17,18,23], to our knowledge, this is the first study identifying
the best non-invasive index using a large sample with a wide range
of hydration statuses under a real competition situation. As a
consequence of the real situation, we detected a large number of
competitors with severe dehydration (176 samples with U
above 701 mOsm?kg H
and 122 samples with U
1.080 mOsm?kg H
) beyond what has been previously
reported [19,37,38]. Also, we observed that independent of sport
discipline and gender a similar distribution of athletes were
dehydrated or extremely dehydrated suggesting, as previously
reported [37–41], that weight cutting is a broadly extended
practice in Olympic combat sports.
Our results indicate that U
is the hydration index that better
correlates with U
(r = 0.89; p = 0.000; Figure 1) the assessment
of U
being easier, cheaper and faster than that of U
. These
results are consistent with the finding of Popowski et al [16] who
compared the validity of U
and U
to plasma osmolality, and
concluded that both, U
and U
correlate and are good
measurements of hydration status. This data is also in agreement
with results from our laboratory [21] reporting that U
is as
sensitive as serum osmolality to detect 2 to 3% hypohydration.
Based on the present results using an important sample size of elite
athletes in a wide range of hydration statuses, we can substantiate
that U
is a highly recommended index to assess hypohydration.
Nevertheless, when dehydration increases U
presents lower
correlation values (G2: r = 0.75; G3: r = 0.66; both p = 0.000;
Figure 1). This validity decline, as body water loss increase, has
been previously observed by Oppliger et al [24]. Nevertheless,
dehydration is usually assessed based on a threshold value that is
much below the values where U
starts to deviate from U
Thus, a lowering in this correlation will rarely affect the
classification of an individual as dehydrated or euhydrated.
Previous studies agreed that U
presents lower precision and
accuracy values to determine the hydration status in humans
compared to U
and U
[17,18,25]. Nevertheless, different
researchers consider that U
would be helpful in athletic, army
or industrial settings where high precision assessment of body fluid
deficit is not required [17,22,25]. Likewise, our data coincides in
that U
is effective at discriminating different levels of
dehydration (Figure 2) despite its lack of preciseness (G2:
r = 0.498; p = 0.002, G3: r = 0.398; p = 0.004; Figure 1). As in
previous studies, we can recommend U
analysis as an index to
estimate hydration status of combat sports athletes; especially
when water loss is not extreme. The low precision level of U
could be offset by its simplicity and low cost to assess hydration
status on the field.
Some studies propose that BIA is a valid tool to assess hydration
status in different populations [26,27,29]. However, our data
suggests that BIA is not a good instrument to assess hydration level
in combat sports athletes (Figure 1). In agreement with our results,
other investigations argued that BIA may be a non-adequate
instrument to evaluate exercise induced dehydration [28,42–44].
Furthermore, our results show that during dehydration and severe
dehydration (G2 and G3) BIA agreement with U
compared to euhydration (G1) (Figure 1). This is in accordance
with the investigation of Asselin et al [45] which indicated that
with dehydration levels of 2–3% of body mass, BIA standard
equations failed to predict changes in total body water. As a
limitation we used segmental BIA but mono-frequency analysis
since, in our experience, this are the technical characteristics of the
BIA equipment commonly found in combat sports clubs and high
performance sports centers. Novel systems of BIA employ multi-
frequency to determine the characteristics of the body fluids and
tissues. Although they have shown even lower validity to estimate
body composition [46], it has been recently reported that they are
sensitive to evaluate acute dehydration in wrestlers [29]. It is
unclear if the use of multi-frequency BIA could have increased its
association with U
in our data set.
Engell et al. [30] showed a high correlation between the
perceived thirst and hypohydration before and after exercise in the
heat. Young et al [33] agreed with this statement and added that
using the 9 point scale (1 = not at all thirsty; 9 = very, very thirsty)
a score between 3 and 5 could be a good indication that an
individual is mildly dehydrated. Our results suggest that this
perception scale is a valid indicator of hydration status, but only
discriminating between euhydration and extreme dehydration.
However, it does not distinguish low levels of dehydration from
correct hydration (Figure 2). Maresh group [31,32] provided data
showing a thigh correlation between hypohydration and thirst
perception when subjects are moderately dehydrated (i.e., ,4%).
It is known that numerous factors, apart from body water deficit,
may alter the perception of thirst such us fluid palatability, time
allowed for fluid consumption, time since last fluid ingestion,
gastric distention, older age, gender, and heat acclimatization
status[17]. Thus, while thirst perception may serve as an indicator
of extreme dehydration, our data suggest that TPS is not accurate
enough to correctly evaluate low and moderate levels of
hypohydration during weight cutting in Olympic combat athletes.
Athletes involved in combat sports (e.g., wrestling, taekwondo
and boxing) habitually weight-cut (i.e. weight loss through
dehydration) to be included in a lower category at the official
weigh-in before competition. Our study compares four different
non-invasive hydration indexes (U
, TPS, and BIA) to
as our gold standard non-invasive measure in a wide sample
of competitive Olympic combat sports athletes. The aim is to find
an alternative measure that, unlike U
, does not involve costly
Figure 2. Descriptive values (whisker and box plot) and group differences according to U
status classification. Also, differences
according to the Kruskal-Wallis test and Dunn’s pairwise comparisons (Bonferroni correction for multiple comparisons).G1: U
250–700 mOsm?kg
; G2: U
701–1.080 mOsm?kg H
; G3.U
1.081–1.500 mOsm?kg H
Validity of Hydration Status Markers
PLOS ONE | 5 April 2014 | Volume 9 | Issue 4 | e95336
biochemical analysis and that can be readily used by sports
medicine doctors, coaches and trainers on the combat arena. Our
data suggests that U
is a good alternative to U
since it highly
correlates with U
, in conditions of low and severe dehydration
(i.e. G2 and G3). However, U
can be an alternative and
adequate tool to evaluate dehydration, especially if the dehydra-
tion level is not extreme. In contrast, our data discourages the use
of TPS and BIA to measure hydration status after weigh-cut in
combat sports athletes.
Author Contributions
Conceived and designed the experiments: VEFE AMA JGP RMR.
Performed the experiments: VEFE AMA RMN JMLG JGP. Analyzed the
data: EDCS JGP RMR. Contributed reagents/materials/analysis tools:
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Validity of Hydration Status Markers
PLOS ONE | 6 April 2014 | Volume 9 | Issue 4 | e95336
... Drinking behaviour, which subsequently affects hydration status, is influenced by thirst and it has been suggested that thirst may provide a valid means of assessing hydration status . However, few studies have examined the perception of thirst as a potential marker of hydration status in professional athletes Fernández-Elías et al., 2014;Hew-Butler et al., 2018). Therefore, the objective of the present study was to determine the hydration status of Czech male soccer league players, and to compare the reported beverage intake, perceived consumption of the beverage and thirst sensation between euhydrated (EU) and dehydrated (DE) athletes. ...
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The objective of this cross-sectional study was to evaluate the hydration status of Czech First League soccer players, and to compare the reported fluid intake, perceived fluid intake and thirst sensation of euhydrated (EU) and dehydrated (DE) players. The study involved 124 Czech male professional soccer players (age 25.2±5.0 years) participating in annual winter, pre-season laboratory testing. Hydration status was assessed based on urine specific gravity (USG), euhydration was set at USG≤1.020. Fluid intake and thirst perception were evaluated by a questionnaire. The sample mean for USG was 1.021±0.008, 56% of players were dehydrated. Reported daily fluid intake was significantly (p<0.001, d=0.95, large effect) higher in EU compared to DE players. Daily fluid intake negatively correlated with USG (rS=-0.46, p<0.001, medium effect). The fluid intake perception score was significantly (p=0.005, d=0.54, medium effect) better in EU compared to DE players. Reported intake perception scores negatively correlated with USG (rS=-0.32, p<0.001, medium effect). However, there was no correlation (rS=-0.09, p=0.34, trivial effect) between thirst perception scores and USG. Thirst perception scores were not significantly different between EU and DE players (p=0.35, d=0.18, trivial effect). Our results indicated that self-assessment of both daily fluid intake and perceived fluid intake matched with objective hydration status, while self-assessment of thirst perception was not an appropriate indicator of hydration status in elite soccer players.
... Other research utilizing BIA as a reference method found large limits of agreement with other techniques, which resulted in significant overestimations and underestimations [4]. Thus, BIA has been proposed as an instrument to evaluate hydration level in combat sport athletes [35], however, other researchers question its validity for this purpose [36]. Furthermore, Hetzlet et al. [37] analyzed the concordance between BIA and anthropometry in wrestlers and concluded that they are not to be used interchangeably. ...
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Combat sports athletes competing in the same discipline exhibit notable and substantial differences in body weight, body composition (BC) and adiposity. No studies have considered the influence of adiposity levels in the agreement between different BC assessment methods. The aim of this study was to analyze the influence of adiposity in the agreement between different methods used to estimate relative body fat (%BF) in Olympic combat sport athletes. A total of 38 male athletes were evaluated using air displacement plethysmography and dual-energy X-ray absorptiometry (DXA) as laboratory methods, and bioelectrical impedance analysis (BIA), near-infrared interactance (NIR) and anthropometry as field methods. All methods were compared to DXA. Agreement analyses were performed by means of individual intraclass correlation coefficients (ICCs) for each method compared to DXA, Bland–Altman plots and paired Student t-tests. The ICCs for the different methods compared to DXA were analyzed, considering tertiles of %BF, tertiles of body weight and type of sport. For the whole group, individual ICCs oscillated between 0.806 for BIA and 0.942 for anthropometry. BIA showed a statistically significant underestimation of %BF when compared to DXA. The agreement between every method and DXA was not affected by %BF, but it was highest in athletes at the highest %BF tertile (>13%). The ICC between NIR and DXA was poor in 72–82 kg athletes. Our results indicate that field methods are useful for routine %BF analysis, and that anthropometry is particularly appropriate, as it showed the highest accuracy irrespective of the athletes’ adiposity.
... Urine specific gravity (USG) is an easy and reliable method to monitor the hydration status of combat sports athletes with urine concentration [27,28]. Each athlete's urine sample was taken immediately before each body mass measurement. ...
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Background: This study aimed to investigate the effect of 5% rapid weight loss on hydration status and judo performance in highly trained judo athletes. Methods: Eighteen male judo athletes participated in the study and were divided into two groups: control and rapid weight loss (RWL). RWL athletes were given 48 h to cut 5% of their body mass while the control group followed their routines. Athletes performed three measurements, including hydration, body mass and three consecutive special judo fitness tests (SJFTs). At the 1st and 6th minutes following each SJFT and 1st, 6th and 15th minutes following the last SJFT, blood lactate and heart rate (HR) was monitored. Results: The effect of RWL on variables was tested with split-plot ANOVA. RWL significantly affected urine specific gravity with a higher value following weight loss compared to baseline and recovery (F2-32 = 13.2, p < 0.001). In addition, athletes' SJFT total throw numbers differed among measurements (F2-32 = 7.70, p < 0.001). Athletes presented worse SJFT index after weight loss (F2-32 = 8.05, p = 0.01; F1-16 = 6.43, p = 0.02, respectively). HR changed significantly among measurements days and times (F28-448 = 143.10, p < 0.001). Conclusion: RWL induced dehydration and impaired heart rate recovery in highly trained judo athletes, and they could not rehydrate between competition simulated weigh-in and 15 h of recovery.
... and serious dehydration (>1.030). USG whose correlation with urine osmolality that is acceptable as gold standard for hydration measurement in combat sports was r = 0.89 (p = 0.000) is accepted as an affordable, valid and reliable tool to monitor hydration status in combat sports (Fernández-Elías et al., 2014). ...
This study aimed to investigate the sex differences in short-term weight change and hydration status in judo athletes. Thirty-five men and 15 women judo athletes voluntarily participated in this descriptive and repeated measures design study. Body mass, urine-specific gravity (USG), and body composition of the athletes were measured at the official weigh-in and the competition day's morning. Body mass of the athletes increased during recovery time between official weigh-in and before the competition (time factor; F 1-48 = 71.81, p < 0.001), this increase was higher in men athletes compared to women athletes (time-sex interaction; F 1-48 = 6.56, p = 0.01). With RWG, USG values of the women and men athletes decreased (time factor; F 1-48 = 8.53, p = 0.005). However, most of the athletes were still in significant or serious dehydration state. Unchanged values of total body water rates (TBW) supported dehydration in athletes before the competition (time factor, F 1-48 = 2.9, p = 0.091; time-sex interaction; F 1-48 = 2.4, p = 0.122). The findings of the study indicated that RWG was higher in men athletes compared to women athletes, but hydration status was not affected by sex factor.Notwithstanding 15 hours of recovery between official weigh-in and the start of the competition, judo athletes were still in dehydrated state despite remaining within the limit set for RWG.
... There are a number of ways to monitor athletes for dehydration. Urinary specific gravity is widely used to certify athletes' hydration status for sports that require athletes to "make weight" (6,10,11). The advantage or urinary specific gravity is that it gives an objective measurement of hydration compared with an expected standard. ...
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Preventing impairments in athletic performance is an important concept for students that are preparing for careers that involve working with athletes. Gaining hands on, laboratory-based experience in measuring exercise induced dehydration can help students understand how to help athletes prevent dehydration induced impairment in performance. This article describes a laboratory exercise for junior and senior students in a sports nutrition class, in which the students measure changes in body mass (as a measure of dehydration) due to 40 min of moderate-intensity exercise and 40 min of vigorous-intensity exercise. The students also measure how much water is in a mouthful from a sports bottle and from a drinking fountain. The students then calculate how many mouthfuls are necessary to replace exercise induced fluid losses. This laboratory exercise has been well received by students and has improved performance on the test regarding hydration.
... The main problem of inadequate body weight regulation is not visible only in wrestling, the same problems occur in other combat sports as boxing, judo, taekwondo, kickboxing athletes and martial mixed arts practitioners [8,14,[18][19][20] as well as other sports with weight categories as rowing and equitation [3] or weight lifting. All research studies but one have indicated negative psychological aspects of RWL; the exception is a study presenting a theory that wrestlers successful in RWL gain mental advantage over their opponents [15]. ...
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Reasons why wrestlers and athletes of other combat sports (boxing, judo, taekwondo, etc.) reduce weight loss are better anthropometric characteristics of wrestlers (longitudinal and skeletal volume) compared to opponents in lower weight categories, better focus and motivation of wrestlers, etc. Main cognitive goal of this research was knowledge about the relationship of rapid weight loss indicators and selected psychological indicators on success of Croatian wrestlers. The research was conducted on 200 Croatian Greco-Roman style wrestlers. The amount of weight loss, the percentage of weight loss, and specific urine density (USG) were determined. Profile of Mood States Questionnaires (POMS), pre-competition anxiety (SCAI-2), goal orientation (TESQ), and intrinsic motivation (IMI) were used. Statistically significant correlation (p = 0.003) of rapid weight loss indicators and selected psychological indicators, with success was determined. Statistically significant correlation was found in the POMS variables (fatigue, p = 0.014), pre-competitive anxiety (self-confidence, p = −0.017), task orientation (p = 0.019) and intrinsic motivation (competence, p = −0.025). Successful wrestlers, despite being dehydrated, are less tired, more interested, more satisfied, have greater confidence and are more task-oriented than less-successful wrestlers. It is assumed that there are differences between age groups of wrestlers which should be investigated by future research.
... A 10 mL quantity was used to obtain the different evaluated parameters. Specific gravity was analyzed in situ with a precalibrated refractometer (URC-Ne, Atago, Japan), as previously described [32]. Biochemical variables (pH, microalbuminuria (MA), erythrocytes) were measured by placing a reagent strip (Combur Test, Roche, Spain) in a small portion of urine samples. ...
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Citation: Pradas, F.; García-Giménez, A.; Toro-Román, V.; Ochiana, N.; Castellar, C. Gender Differences in Neuromuscular, Haematological and Urinary Responses during Padel Matches. Int. J. Environ. Res. Public Health 2021, 18, 5864. Abstract: Research on the acute physiological response to a padel match is limited. The present study aimed to: (a) evaluate neuromuscular, urinary, and hematological responses after simulated padel competition (SC) and (b) analyze possible gender differences. In this study, 28 high-level padel players participated (men = 13, age = 26.83 ± 6.57 years; women = 15, age = 30.07 ± 4.36 years). The following parameters were analyzed before and after SC: neuromuscular (hand grip strength, squat jump (SJ), countermovement jump (CMJ), and Abalakov jump (ABK)), hematological (red blood cells, hemoglobin, and hematocrit), and urinary (pH, specific gravity, microalbuminuria, and red blood cells). Significant gender differences were found in neuromuscular and hematological responses, with men obtaining higher values (p < 0.05). For the SC influence, changes were noted in ABK and microalbuminuria (p < 0.05). The percentages of change in hand grip strength, SJ (height and watts), CMJ (height), and ABK (height) were higher for men than women (p < 0.05). SC negatively influenced the neuromuscular parameters to a greater extent in women. Our results could be related to gender differences in game actions, the temporal structure, and anthropometric and physiological characteristics. Game dynamics and a different organic response between male and female padel playing were confirmed.
... Water allows for homeostasis, facilitates most biochemical reactions, and allows numerous particles and compounds to dilute. It helps in the transport of metabolites and utilization of by-products [10,11]. Several comprehensive reviews of the effect of dehydration on local muscular endurance, strength, anaerobic capacity, jumping performance, and specific sport skills in team sports games have revealed negative effects of dehydration <2% body mass [6,12,13]. ...
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In combat sports, anaerobic power and anaerobic capacity determine sport performance and the dominant metabolic pathways. The decline in performance during exercise that is attributed to the cumulative effects of fatigue, including excessive accumulation of metabolites, depletion of energy substrates, and water and electrolyte disturbances, seems to be of greatest significance. In our experiment, we evaluated the effectiveness of three weeks of bicarbonate-rich water ingestion on anaerobic performance in a state of hydration and dehydration in elite judo athletes. Eight male, elite judo athletes participated in two single-blind, repeated-measures trials. They were assigned to two hydration protocols, ingesting low mineralized table water and bicarbonate-rich water. Anaerobic performance was evaluated by two 30 s Wingate tests for lower and upper limbs, respectively, under conditions of hydration as well as exercise-induced dehydration. Resting, post-ingestion, and post-exercise concentrations of bicarbonate (HCO3), urine osmolality (UOSM), urine specific gravity (UGRAV), and lactate (La) were measured. The current investigation assessed two related factors that impair anaerobic performance—hypohydration and buffering capacity. High-bicarbonate water ingestion improved buffering capacity, and we demonstrated the potential role of this mechanism and its phenomenon in masking the adverse effects of dehydration in the context of repeated high-intensity anaerobic exercise (HIAE).
... The magnitude of the percentage of weight athlete's loss varies depending on the time they implement the strategy before the official weigh-in. RWL occurs often (Artioli et al., 2010b;Brito et al., 2012;Franchini et al., 2012;Khodaee et al., 2015) with the aim to qualify in a class lower than the athletes training weight, seeking to gain an advantage by competing against lighter, smaller and weaker opponents (Artioli et al., 2010d;Fernández-Elías et al., 2014;Reale et al., 2016b) These practices take place within a structural, social and cultural context. There are studies that tell us about the adoption of the practices, how the rules are accepted within the sports community becoming a key part of the sport and, as a consequence, these practices are well-established. ...
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The practice of strategies for rapid weight loss (RWL) involve diverse factors, such as individual expectations, social interactions, structural elements, etc., conforming to a “culture” of RWL, which must be evaluated and understood in a broad sense. Based on the need of a comprehensive evaluation of the use of RWL in practitioners of combat sports, an ad hoc questionnaire designed for this study, which includes the types and detailed descriptions of RWL strategies, that athletes currently use, the prevalence and frequency of use, the physiological and psychological consequences, the perception of the effect of RWL on their own performance and finally, the individuals who influence the adoption of this practice. One hundred and sixty combat athletes from wrestling and taekwondo disciplines, from Mexico, filled out this questionnaire. Data collected for their statistical analyses. Results revealed a RWL strategies prevalence of 96% across the participants. Our results revealed that 57% of those athletes using RWL lose more than 5% of their body mass. Across the athletes, the most commonly used RWL strategies and with higher intensity were increased exercise and training with plastic or thick clothes. The greater the relative weight loss, the greater the presence of physiological symptoms in athletes, such as rapid breathing and blood pressure. Athletes also mentioned mood states such as tiredness, sadness, confusion, fatigue and vigor, these last two positive and negative mood states are associated with the relative weight loss, respectively. Finally, the people who most influenced the adoption of RWL strategies were the coaches, parents and nutritionists. In conclusion, the questionnaire prepared for this study allowed us to obtain valuable information about the several factors, and their interactions, involved in the practice of RWL in combat athletes. This type of practice could increase health risks and decrease their performance. Therefore, here we state the importance of a comprehensive evaluation of RWL strategies that allows the development of psycho-educational and social-based interventions and programs for the promotion of proper weight maintenance, and prevention against RWL strategies, involving the individuals who influence the adoption of these practices and supporting it with the help of communication technologies.
Background: Heat waves are known to cause increased morbidity and mortality in susceptible populations like old and functionally impaired people. The objective of the study was to assess renal tubular stress, a predictor for development of acute kidney injury, during heat waves in Central Europe. As a marker of renal tubular stress tissue inhibitor of metalloproteinases-2 [TIMP-2]·insulin-like growth factor binding protein-7 [IGFBP7], a new FDA-cleared renal tubular stress biomarker, was used. Materials and methods: 68 residents from facilities of sheltered housing with urine samples collected at heat waves in 2015 and at control visits were included. Urinary [TIMP-2]·[IGFBP7] was compared between the heat waves and the control visits. Multivariate linear models were adjusted for age, frailty index, and functional comorbidity index. Results: The median age was 82.0 years, 82.3% were women. The percentage of elevated levels of urinary [TIMP-2]·[IGFBP7] (>0.3 [ng/mL]2/1,000) in the total study population was higher at the heat waves than at the control visits (25.0% vs. 17.7%). The effect of the heat waves on urinary [TIMP-2]·[IGFBP7] was stronger in men than in women: The percentage of elevated levels was 75.0% in men and 14.3% in women. In the multivariate analysis, the mean urinary [TIMP-2]·[IGFBP7] was 0.48 (95% CI 0.25; 0.70) (ng/mL)2/1,000 higher in men than in women. Except gender, a number of additional variables did not show an association with urinary [TIMP-2]·[IGFBP7] at the heat waves or the control visits. Conclusions: At heat waves, urinary [TIMP-2]·[IGFBP7] was elevated and higher in men than in women. This suggests gender-specific differences in renal heat tolerance in older people.
To assess the effects of rapid weight reduction, four university wrestlers decreased their body weight by 8% over a four-day period by food and liquid intake reductions. Significant decreases in muscle glycogen concentration and dynamic strength, but not aerobic or anaerobic capacity, accompanied weight loss. A three-hour rehydration period did not improve glycogen levels or strength performance. These results suggest that rapid weight reduction may impair wrestling performance.
Weight category athletes are known for practicing rapid weight loss prior to competition weigh-in. After weigh-in, athletes strive to restore euhydration and body mass through food and fluid intake. The aim of the present study was to assess prevalence of hypohydration at competition time among elite athletes' in four different combat sports, and how water intake and timing of official weigh-in were related to hydration status. Participants were 31 taekwondo practitioners and wrestlers who performed evening weigh-in (EWI) the night before competition day and had thus time for rehydration, and 32 boxers and judokas conducting competition day morning weigh-in (MWI). In total, 32% were female. Urine specific gravity (USG) was measured by refractometry on the competition day's first morning urine sample. Hypohydration was defined as USG ≥1.020 and serious hypohydration as USG>1.030. Water intake was measured by means of dietary records. The prevalence of hypohydration was 89% in the morning of competition day. Serious hypohydration was also prevalent. This was found in over 50% of MWI athletes and was also present in 42% of the EWI group. A higher water intake, from both fluids and solid foods, in the evening before competition day was not associated with a more favourable hydration status the following morning. In conclusion, neither weigh-in close to competition nor evening weigh-in with more time for rehydration seems to prevent hypohydration prior to competition.
This paper considers the use of rank sums from a combined ranking of k independent samples in order to decide which populations differ. Such a procedure is suggested as a convenient alternative to making separate rankings for each pair of samples, and the two methods are compared. Asymptotic use of the normal tables is given and the treatment of ties is discussed. A numerical example is given.
We assessed the urinary indexes of hydration status of Greco-Roman wrestlers in an authentic precompetition situation at the time of official weigh-in (OWI). A total of 51 of 89 wrestlers competing in the Estonian Championship in 2009 donated a urine sample. Questionnaire responses revealed that 27 wrestlers (body mass losers (BMLs)) reduced body mass before the competition, whereas 24 wrestlers (those who do not lose body mass (n-BMLs)) did not. In 42 wrestlers, values of urine specific gravity ≥1.020 and urine osmolality ≥700 mOsmol·kg(-1) revealed a hypohydrated status. The prevalence of hypohydration in the BMLs (96%) was higher than in the n-BMLs (67%) (χ(2) = 7.68; p < 0.05). The prevalence of serious hypohydration (urine specific gravity >1.030) was 5.3 times greater (χ(2) = 8.32; p < 0.05) in the BMLs than in the n-BMLs. In the BMLs, the extent of body mass gain during the 16-h recovery (2.5 ± 1.2 kg) was associated (r = 0.764; p < 0.05) with self-reported precompetition body mass loss (4.3 ± 2.0 kg) and exceeded the body mass gain observed in the n-BMLs (0.7 ± 1.2 kg; p < 0.05). We conclude that hypohydration is prevalent among Greco-Roman wrestlers at the time of OWI. The prevalence of hypohydration and serious hypohydration is especially high among wrestlers who are accustomed to reducing body mass before competition. These results suggest that an effective rehydration strategy is needed for Olympic-style wrestlers, and that changes in wrestling rules should be considered to reduce the prevalence of harmful body mass management behaviours.
Context: The combination of extensive weight loss and inadequate nutritional strategies used to lose weight rapidly for competition in weight-category sports may negatively affect athletic performance and health. Objective: To explore the reasoning of elite combat-sport athletes about rapid weight loss and regaining of weight before competitions. Design: Qualitative study. Setting: With grounded theory as a theoretical framework, we employed a cross-examinational approach including interviews, observations, and Internet sources. Sports observations were obtained at competitions and statements by combat-sport athletes were collected on the Internet. Patients or other participants: Participants in the interviews were 14 Swedish national team athletes (9 men, 5 women; age range, 18 to 36 years) in 3 Olympic combat sports (wrestling, judo, and taekwondo). Data collection and analysis: Semistructured interviews with 14 athletes from the Swedish national teams in wrestling, judo, and taekwondo were conducted at a location of each participant's choice. The field observations were conducted at European competitions in these 3 sports. In addition, interviews and statements made by athletes in combat sports were collected on the Internet. Results: Positive aspects of weight regulation other than gaining physical advantage emerged from the data during the analysis: sport identity, mental diversion, and mental advantage. Together and individually, these categories point toward the positive aspects of weight regulation experienced by the athletes. Practicing weight regulation mediates a self-image of being "a real athlete." Weight regulation is also considered mentally important as a part of the precompetition preparation, serving as a coping strategy by creating a feeling of increased focus and commitment. Moreover, a mental advantage relative to one's opponents can be gained through the practice of weight regulation. Conclusions: Weight regulation has mentally important functions extending beyond the common notion that combat-sport athletes reduce their weight merely to gain a physical edge over their opponents.
The purpose of this study was to characterize the magnitude of acute weight gain (AWG) and dehydration in mixed martial arts (MMA) fighters prior to competition. Urinary measures of hydration status and body mass were determined ∼24 h prior and then again ∼2 h prior to competition in 40 MMA fighters (Mean ± SE, age: 25.2 ± 0.65 yr, height: 1.77 ± 0.01 m, body mass: 75.8 ± 1.5 kg). AWG was defined as the amount of body weight the fighters gained in the ∼22 h period between the official weigh-in and the actual competition. On average, the MMA fighters gained 3.40 ± 2.2 kg or 4.4% of their body weight in the ∼22 h period prior to competition. Urine specific gravity significantly decreased (P < 0.001) from 1.028 ± 0.001 to 1.020 ± 0.001 during the ∼22 h rehydration period. Results demonstrated that 39% of the MMA fighters presented with a Usg of greater than 1.021 immediately prior to competition indicating significant or serious dehydration. MMA fighters undergo significant dehydration and fluctuations in body mass (4.4% avg.) in the 24 h period prior to competition. Urinary measures of hydration status indicate that a significant proportion of MMA fighters are not successfully rehydrating prior to competition and subsequently are competing in a dehydrated state. Weight management guidelines to prevent acute dehydration in MMA fighters are warranted to prevent unnecessary adverse health events secondary to dehydration.
The purpose of this investigation was to compare the effects of oral and intravenous saline rehydration on differentiated ratings of perceived exertion(RPE) and thirst. Eight men underwent three randomly assigned rehydration treatments following a 2- to 4-h exercise-induced dehydration bout to reduce body weight by 4%. Treatments included 0.45% saline infusion (IV), 0.45% saline oral ingestion (ORAL), and no fluid (NF). Following rehydration and rest (2 h total), subjects walked at 50% ˙VO2max for 90 min at 36°C (EX). Central RPE during ORAL was lower (P < 0.05) than IV and NF throughout EX. Local RPE during NF was higher (P < 0.05) than IV and ORAL at minutes 20 and 40 of EX and overall RPE during NF was higher (P < 0.05) than ORAL at minutes 20 and 40 of EX. Significant correlations were found between overall RPE and mean skin temperature for IV (r = 0.72) and NF (r = 0.75), and between overall RPE and thirst ratings for IV (r = 0.70). Thirst ratings were not different among trials at postdehydration. Following rehydration, thirst was higher(P < 0.05) during NF than IV and ORAL and lower (P < 0.05) during ORAL than IV at all subsequent time points. Results suggest that oral rehydration is likely to elicit lower RPE and thirst ratings compared with intravenous rehydration.
Blood serum osmolality (S OSM) is the gold standard to assess body fluid balance. Urine specific gravity (U SG) is also a body fluid balance index but it is not invasive. However, U SG capability to detect the minimal level of dehydration that affects athletic performance (i.e., 2 %) remains untested. We collected urine and blood samples in eighteen euhydrated trained athletes in the morning and that evening while dehydrating by 1, 2, and 3 % of body mass by cycling (60 % \( \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} \)) in the heat (32 °C, 46 % rh, 2.5 m s−1 air flow). At 9:00 pm, subjects left the laboratory and went to bed after ingesting 0.7 ± 0.2 L of a sports drink. The next morning, subjects awoke 3 % hypohydrated, and blood and urine samples were collected and test terminated. We found that 2 % dehydration increased S OSM and U SG above exercise-baseline values (P
The objective of this study was to examine the validity of multifrequency direct segmental bioelectrical impedance analysis (DSM-BIA) measures to detect changes in the hydration status of wrestlers after they underwent 3% acute dehydration and a 2-hour rehydration period. Fifty-six National Collegiate Athletic Association wrestlers: (mean ± SEM); age 19.5 ± 0.2 years, height 1.73 ± 0.01 m, and body mass (BM) 82.5 ± 2.3 kg were tested in euhydrated, dehydrated (-3.5%), and 2-hour rehydration conditions using DSM-BIA to detect the changes in hydration status. The hydration status was quantified by measuring the changes in plasma osmolality (P(osm)), urine osmolality (Uosm), urine specific gravity (U(sg)), BM, and weighted segmental impedance at frequencies of 5, 20, 50, 100, and 500 kHz. Weighted segmental impedance significantly increased after a 3.5% reduction in the body weight for all the 5 frequencies evaluated, but it did not return to baseline at 2-hour rehydration. P(osm) (303 ± 0.6 mOsm·L(-1)), Uosm (617 ± 47 mOsm·L(-1)), and U(sg) (1.017 ± 0.001) all significantly increased at postdehydration and returned to baseline at 2-hour rehydration. Estimations of extracellular water were significantly different throughout the trial, but there were no significant changes in the estimations of the total body water or intracellular water. The results of this study demonstrate the potential use of DSM-BIA as a field measure to assess the hydration status of wrestlers for the purpose of minimal weight certification before the competitive season. When employing DSM-BIA to assess the hydration status, the results indicated that the changes in weighted segmental impedance at the frequencies evaluated (5, 20, 50, 100, and 500 kHz) are sensitive to acute changes in dehydration but lag behind changes in the standard physiological (plasma and urinary) markers of hydration status after a 2-hour rehydration period.