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R E S E A R C H A R T I C L E Open Access
Muscle contraction velocity, strength and
power output changes following different
degrees of hypohydration in competitive
olympic combat sports
J. G. Pallarés
1,2
, A. Martínez-Abellán
1
, J. M. López-Gullón
1
, R. Morán-Navarro
1,2
, E. De la Cruz-Sánchez
1
and R. Mora-Rodríguez
2*
Abstract
Background: It is habitual for combat sports athletes to lose weight rapidly to get into a lower weight class. Fluid
restriction, dehydration by sweating (sauna or exercise) and the use of diuretics are among the most recurrent
means of weight cutting. Although it is difficult to dissuade athletes from this practice due to the possible negative
effect of severe dehydration on their health, athletes may be receptive to avoid weight cutting if there is evidence
that it could affect their muscle performance. Therefore, the purpose of the present study was to investigate if
hypohydration, to reach a weight category, affects neuromuscular performance and combat sports competition
results.
Methods: We tested 163 (124 men and 39 woman) combat sports athletes during the 2013 senior Spanish
National Championships. Body mass and urine osmolality (U
OSM
) were measured at the official weigh-in (PRE) and
13–18 h later, right before competing (POST). Athletes were divided according to their U
SOM
at PRE in euhydrated
(EUH; U
OSM
250–700 mOsm · kgH
2
O
−1
), hypohydrated (HYP; U
OSM
701–1080 mOsm · kgH
2
O
−1
) and severely
hypohydrated (S-HYP; U
OSM
1081–1500 mOsm · kgH
2
O
−1
). Athletes’muscle strength, power output and contraction
velocity were measured in upper (bench press and grip) and lower body (countermovement jump - CMJ) muscle
actions at PRE and POST time-points.
Results: At weigh-in 84 % of the participants were hypohydrated. Before competition (POST) U
OSM
in S-HYP and
HYP decreased but did not reach euhydration levels. However, this partial rehydration increased bench press
contraction velocity (2.8-7.3 %; p< 0.05) and CMJ power (2.8 %; p< 0.05) in S-HYP. Sixty-three percent of the
participants competed with a body mass above their previous day’s weight category and 70 of them (69 % of that
sample) obtained a medal.
Conclusions: Hypohydration is highly prevalent among combat sports athletes at weigh-in and not fully reversed
in the 13–18 h from weigh-in to competition. Nonetheless, partial rehydration recovers upper and lower body
neuromuscular performance in the severely hypohydrated participants. Our data suggest that the advantage of
competing in a lower weight category could compensate the declines in neuromuscular performance at the onset
of competition, since 69 % of medal winners underwent marked hypohydration.
Keywords: Hydration, Urine osmolality, Bench press, Taekwondo, Olympic wrestling and boxing
* Correspondence: Ricardo.Mora@uclm.es
2
Exercise Physiology Laboratory, University of Castilla-La Mancha, Toledo,
Spain
Full list of author information is available at the end of the article
© 2016 Pallarés et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10
DOI 10.1186/s12970-016-0121-3
Background
Olympic weight-class combat sports (i.e., wrestling, box-
ing, judo and taekwondo) match their athletes before
competition, separating them by sex and weight class.
Weight class divisions have the purpose of making com-
petition fair by matching opponents of similar muscle
mass and strength and by doing so, reducing the risk of
injury [1, 2]. However, the timing between weigh-in and
competition can turn this noble purpose into a perverse
rule. In Olympic weight-class sports the official weigh-in
is typically held 6–24 h before competition for both the
amateur and professional fighters. This allows most ath-
letes to use aggressive weight-cut practices to lose
weight and enter competition in a lower weight class,
followed by fast weight regain during the hours before
competition.
In 1997 dehydration ranging from 7–10 % contributed
to the death of three collegiate level wrestlers in the
USA. Those episodes persuaded authorities to advance
the weigh-in period to 1–2 h before competition in high
school and collegiate wrestling. Unfortunately, this rule
has not spread into the European or international feder-
ations of any combat sport and, as a consequence,
weight-cutting practices prevail [3]. The American Col-
lege of Sports Medicine (ACSM) has, for long time, been
suggesting that athletes should not lower their body
mass below the weight at which body fat levels are lower
than 5 % [4]. Thus, minimal combat weight has habit-
ually been established based on body fat estimations (i.e.,
skinfolds or bioimpedance [5]), while educational pro-
grams have been administered [6] to prevent rapid
weight loss practices inducing severe dehydration in
combat athletes. Nevertheless, the success of these edu-
cational programs is tenuous [7] since approximately
one third of these athletes compete below their calcu-
lated minimal weight and are still very successful [8].
The reluctance of the combat sports ruling authorities
to impede these weight-cut practices despite the accu-
mulation of scientific literature showing the negative ef-
fects of hypohydration on performance and health
seems peculiar. However, it is understandable that ath-
letes and their coaches do not take into account the
negative effects of hypohydration on their physical per-
formance, compared to the advantage of competing in a
lower weight category. To our knowledge, one study
stands alone addressing whether competition results are
negatively correlated with body mass gained between
weigh-in and competition (an index of initial dehydra-
tion). The results reported in that study do not discour-
age athletes from undergoing weight cutting practices
[8]. This is, 60 % of the wrestlers below their minimal
competition weight ranked among the first 4 in each cat-
egory, while only 33 % of the wrestlers in their natural
combat body mass were winners during the competition.
Losses of fat mass require weeks of dieting, and
losses of the carbohydrate stored in the body can
only account for ~0.5 kg of body mass loss. Thus,
most of the weight loss achieved by these combat
sport athletes during weight-cut is due to loss of body
water. Extreme reductions in fluid and food intake,
sauna exposure, diuretic pills use [7] and exercise
using rubberized sweat suits are common means used
by combat sport athletes to reduce body mass during
the days prior to weigh-in [2]. Hypohydration nega-
tively impacts on the capacity of the body to thermo-
regulate, resulting in increased core temperature
during exercise [9]. In turn, hyperthermia has been
repeatedly shown to result in premature fatigue dur-
ing intense aerobic exercise [10, 11]. In addition,
hypohydration and the resulting hyperthermia, in-
duces cardiovascular drift, which is associated with
performance impairments such as declines in cycling
peak power [12], anaerobic power and maximal aer-
obic capacity [13].
Although success in Olympic combat sports is multi-
factorial, recent studies have shown that muscle strength
and power are key factors affecting performance in these
sports [1, 14]. However, the effects of rapid dehydration
and rehydration on neuromuscular performance (i.e.,
muscle strength and power) have not been sufficiently
explored. Weight loss by dehydration has been shown to
affect boxing and wrestling performance [13, 15]. How-
ever, if the weight loss is quickly recovered, the effects
on performance are not evident [16]. Maximal isometric
muscle strength is found to be either reduced [17] or
unchanged [18] after rapid weight loss. Montain and co-
workers found that 4 % dehydration reduced muscle en-
durance, but not isokinetic knee extension strength,
while neither pH or Pi were affected by hypohydration
[19]. Nevertheless, recent studies argue that hypohydra-
tion may impair isometric-eccentric strength, and par-
ticularly the rate of force development [20, 21].
Therefore, the purpose of this study was to determine
whether the hypohydration which competitive Olympic
combat sport athletes undergo to get into a lower
weight-class category, reduces their neuromuscular per-
formance. In addition, we investigated whether the mag-
nitude of body mass gained between the weigh-in and
the beginning of competition (an index of initial dehy-
dration) is related to the performance results in a real
competition event.
Methods
Subjects
One hundred and twenty-four male (age 22.4 ± 4.3
years, body mass 75.1 ± 14.7 kg, height 177.1 ± 7.1 cm)
and thirty nine female (age 22.7 ± 4.4 years, body mass
56.9 ± 8.8 kg, height 164.7 ± 7.0 cm) high performance
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 2 of 9
athletes of three different Olympic combat sports volun-
teered to participate in this study: wrestling (n= 76),
taekwondo (n= 62) and boxing (n= 25). This sample
can be considered representative of the population stud-
ied, not only for its size in absolute terms, but because
these 163 participants represented 61.7 % of all athletes
competing at the 2013 Spanish National Championship
in these three Olympic combat sports. All participants
had at least 4 years of training and competition experi-
ence. Athletes and coaches were informed in detail
about the experimental procedures and the possible risks
and benefits of the project. The study complied with the
Declaration of Helsinki and was approved by the Bioeth-
ics Commission of the University of Murcia. Written in-
formed consent was obtained from athletes prior to
participation. The four medal winners of each weight
category (1
st
,2
nd
and the two 3
rd
classified) in the
Spanish National Championship were grouped as the
Elite group. The remaining participants were assigned
to the non-Elite group [1, 14].
Experimental approach to the problem
Athletes’body mass, hydration status and neuromus-
cular performance were evaluated on two separate oc-
casions: i) between 60 and 5 min before the official
weigh-in of their respective National Championship
(PRE) and, ii) between 60 and 5 min before the be-
ginning of the first combat bout (POST). PRE trials
were conducted between 16:00 and 19:00 h, and
POST trial between 8:00 and 10:00 h the following
day. No instructions were given to athletes or their
coaches about weight control management. Eight sub-
jects were excluded from the study for ingesting vita-
mins, nutritional supplements or prescription drugs
prone to alter urine composition [22]. Three women
were excluded because they were in the proliferative
phase of their menstrual cycle which could alter urine
composition. In addition, 20 subjects were not
allowed to participate in the study due to lack of
familiarization with the weight lifting procedures.
At arrival to the testing facilities, a 10 ml mid flow
urine sample was obtained from each athlete. After the
tube with the urine sample was handed over and codi-
fied, subjects’body mass was determined and fat-free
mass percentage estimated using a calibrated scale
(Tanita BC-418, Tanita Corp., Tokyo, Japan). Urine spec-
imens were immediately analyzed for urine osmolality
(U
OSM
) by the same experienced investigator. After a
standardized warm-up that consisted of 5 min of joint
mobilization exercises, the subjects entered the labora-
tory to start the neuromuscular test battery assessments
under a paced schedule. These tests consisted of i) the
measurement of bar displacement velocity against 3 to 5
incremental loads in the bench press exercise, ii)
maximal isometric grip strength test, and iii) counter-
movement jump height test. Only participants who re-
ported being familiar with these resistance training
exercises were included in the study (final sample 163
combat sport athletes). Neuromuscular testing was com-
pleted for all participants in the three National Champi-
onships and two time points (PRE and POST) at the
same human performance laboratory close to the official
weigh-in and competition facilities.
Procedures
Isoinertial strength assessment
After a warm-up for bench press exercise (i.e., 2 sets of
10 repetitions against 20 kg and 35 kg) all participants
performed a graded submaximal loading test in a Smith
machine (Multipower Fitness Line, Peroga, Spain) with a
linear encoder and its associated software (T-Force Sys-
tem, Ergotech, Murcia, Spain, 0.25 % accuracy) attached
to the bar by a light retractable metal cable. The initial
load was set at 20 kg for all participants and was grad-
ually increased by 20 kg for men and 10 kg for women
until mean propulsive velocity was between 0.60 m · s
−1
and 0.50 m · s
−1
(~70–80 % 1RM; [23]). To attain that
propulsive velocity each participant lifted between 3 to 5
increasing loads. The same warm up and loads per-
formed during the PRE trial (i.e., before the official
weigh-in) were replicated in the POST trial (i.e., before
the beginning of the tournament).
Mean propulsive velocity (MPV) was calculated as the
average velocity measured only during the propulsive
phase, defined as the portion of the concentric action
during which the bar acceleration is greater than acceler-
ation due to gravity [23]. In each trial (PRE and POST),
three repetitions were executed for light (MPV between
1.40 and 1.00 m · s
−1
), two for medium (MPV between
0.99 and 0.75 m · s
−1
), and only one for the heaviest
(MPV between 0.74 and 0.50 m · s
−1
) loads interspersed
with 5-min of passive rest.
Individual range of movement was carefully replicated
in each trial with the help of two telescopic bar holders
with a precision of ± 1.0 cm. The bar holders were posi-
tioned to allow the bar to descend to 1 cm off each sub-
ject’s chest. Subjects were instructed to perform the
eccentric phase in a slow and controlled manner, remain
paused for 2 s at the bar holders, momentarily releasing
the weight, and thereafter to perform a purely concentric
action, pushing at the maximal possible velocity. The
momentary pause imposed between the eccentric and
concentric actions was designed to minimize the contri-
bution of the stretch-shortening cycle (i.e., rebound ef-
fect) and allow for a more reliable and consistent
measurement [23].
Given the close relationship between the bar mean
propulsive velocity (i.e., MPV) attained during the
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 3 of 9
concentric phase and the load (% 1RM; r > 0.995 [24]) it
was not necessary to reach the one repetition maximum
load (1RM) to quantify the effects that the 13–18 h that
separated the PRE and the POST time points had on
neuromuscular performance. We analyzed the MPV dif-
ference between the PRE and POST trials against the
heaviest load lifted during the incremental loading test
(MPV between 0.60 and 0.50 m · s
−1
). As recently re-
ported, the MPV at this load represents the most valid
and reliable test to predict maximum strength through
bar displacement velocity [23, 24]. In addition, this pro-
cedure avoids the physical and mental stress associated
with 1RM assessment, it drastically reduces testing time
and injury risk.
Jumping test (CMJ)
Participants completed three repetitions of a counter-
movement vertical jump (CMJ). For this test, partici-
pants squatted down into a self-selected depth prior to
explosively performing the concentric action. Partici-
pants were instructed to keep their hands on their hips
at all times and to maintain the same position at take-off
and landing. Flight times were measured using an infra-
red jump system (Optojump, Microgate, Italy). The re-
corded height for this test was the average of three trials.
Absolute mechanical power during CMJ was calculated
with the following formula: CMJ
P
= BM g (2 g h)
1/2
in
which “BM”is body mass in kg, “g”the acceleration of
gravity in m s
−2
, and “h”the jumping height in meters.
The detailed testing procedures, validity, and reliability
(i.e., test–retest ICC and CV were 0.94 and 3.3 %, re-
spectively) have recently been established elsewhere [1].
Maximal hand grip strength tests
Each subject’s grip strength was measured for dominant
and non-dominant hands with a Baseline Hydraulic
Dynamometer (Country Technology Inc; Gays Mills,
USA). Participants sat with 0° of shoulder flexion and
90° of elbow flexion and the forearm in neutral position.
The average result of two repetitions with each arm was
recorded.
Urine osmolality
U
OSM
isthemeasureofthetotalurinesolutecontent.
As has been repeatedly reported, this procedure is
considered the gold standardnon-invasivemeasureto
determine the athletes’hydration status [3, 25]. Upon
collection, athlete’s urine specimens (10 mL) were im-
mediately analyzed in duplicate by freezing point
depression osmometry (Model 3250, Advanced Instru-
ments, USA).
Statistical analysis
Standard statistical methods were used for the calcu-
lation of means, standard deviation (SD), standard
error of the means (SEM) and effect size (ES). Subjects
were stratified in three groups according to their hydration
status based on U
OSM
values [26] at PRE data collection. As
recently described [3] three intervals of equal amplitude
were established according to the following cutoff values:
from 250 to 700 mOsm · kg H
2
O
−1
(euhydrated -
EUH; n= 26), from 701 to 1.080 mOsm · kg H
2
O
−1
(hypohydrated - HYP; n= 69) and from 1.081 to
1.500 mOsm · kg H
2
O
−1
(severely hypohydrated - S-
HYP; n= 68). The Shapiro-Wilk test was used to
assess normal distribution of data. A two-way (hydra-
tion level x time) ANOVA was used to detect differ-
ences in U
OSM
values. One-way ANOVA was run for
comparison of change scores (PRE vs. POST) in body
composition and neuromuscular performance vari-
ables. The Greenhouse-Geisser adjustment for spher-
icity was calculated. After a significant F test,
differences among means were identified using pair-
wise comparisons with Bonferroni’sadjustment.Dif-
ferences in the change scores between the elite and
non-elite groups were analysed using Student’sttest.
Additionally, a chi-square test for association was
conducted between competitive levels and hydration
status, with all expected cell frequencies greater than
five. The p< 0.05 criterion was used for establishing
statistical significance.
Results
Urine osmolality and body mass
When the PRE urine osmolality results of the three groups
were compared, S-HYP 1215 ± 95 mOsm · L
−1
;SEM=12
mOsm · L
−1
) showed significantly higher values than HYP
(975 ± 79 mOsm · L
−1
SEM = 9 mOsm · L
−1
;24.6%
higher; ES = 2.74; p< 0.001) and EUH (618 ± 187 mOsm ·
L
−1
; SEM = 37 mOsm · L
−1
;96.4%higher;ES=
4.22; p< 0.001). Significantly higher U
OSM
values
were detected in the HYP compared to EUH in PRE
(57.7 % higher; ES = 2.67; p< 0.001). Similarly, POST
U
OSM
in S-HYP (1000 ± 185 mOsm · L
−1
;SEM=22
mOsm · L
−1
) was significantly higher than HYP (883 ±
224 mOsm · L
−1
; SEM = 26 mOsm · L
−1
; 13.3 % higher;
ES = 0.57; p< 0.02) and EUH (749 ± 238 mOsm · L
−1
;
SEM = 48 mOsm · L
−1
; 33.5 % higher; ES = 1.18;
p< 0.001). Also, significant higher values were de-
tected in the HYP compared to EUH at POST
(17.8 % higher; ES = 0.58; p<0.001;Fig.1).
U
OSM
changed between PRE and POST time points in
all groups. The euhydrated group (EUH) significantly in-
creased its osmolality in the 13–18 h that separated the
official weigh-in and the beginning of the tournament
(21.2 %; ES = 0.61; p< 0.01). By contrast, the
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 4 of 9
hypohydrated (HYP) and severely hypohydrated (S-HYP)
groups significantly decreased their urine osmolality (i.e.,
rehydration) in the same period of time (HYP = −9.5 %,
ES = 0.61; p<0.01;S-HYP=−17.7 %, ES = 1.53; p<0.01;
Fig. 1).
Body mass difference between PRE and POST time
points (i.e., another index of rehydration) did not change
for the euhydrated group (i.e., EUH). However, the hypo-
hydrated group HYP recovered 1.2 % of body mass and
the group severely hypohydrated (i.e., S-HYP) recovered
3.1 % of body mass. The recovery in the S-HYP group
was higher than the recovery in the rest of the groups
(ES = 0.49 –1.41; p< 0.05; Fig. 2).
A strong linear negative correlation was detected be-
tween body mass changes and U
OSM
changes between
thePREandPOSTtimepointsinthewholesample
(r= 0.504; p< 0.001; n= 163; Fig. 3).
Neuromuscular assessments
The increases in MPV in the severely hypohydrated
group (i.e., S-HYP) was higher than in the EUH and
HYP groups (7.3 ± 2.6 % compared to −3.4 ± 2.6 % for
EUH and 0.2 ± 1.4 % for HYP; p< 0,001; Fig. 4a). Like-
wise, significantly higher CMJ power increases were de-
tected in the S-HYP group (2.8 ± 3.9 %) compared to
EUH (−0.6 ± 4.7 %; ES = 0.79; p< 0.001) and close to
significance when compared to HYP (1.1 ± 3.1 %; ES =
0.49; p= 0.08; Fig. 4b). No significant differences were
detected in the relative changes of maximum grip
strength for dominant or non-dominant hands, neither
between PRE and POST values, nor between groups
(EUH, HYP and S-HYP) at any time point (Fig. 4c).
Results by competitive level
When PRE hydration status of all medals winners at
their respective National Championships (Elite) were
compared to the remaining competitors (i.e., non-Elite),
Elite showed higher mean urine osmolality (Elite =
1034.3 ± 28.6 mOsm · kg H
2
O
−1
; non-Elite = 955.8 ±
22.4 mOsm · kg H
2
O
−1
;p< 0.05). Chi-squared test
showed a significantly higher proportion of severe dehy-
dration (U
OSM
> 1080 mOsm · kg H
2
O
−1
) in the Elite
group (46.8 % vs. 26.2 %; χ2(2) = 7.519, p= 0.023). How-
ever, no significant differences were detected between
competitive levels before the beginning of the tourna-
ment (i.e., POST; Elite = 906.8 ± 28.1 mOsm · kg H
2
O
−1
;
non-Elite = 888.0 ± 22.9 mOsm · kg H
2
O
−1
). Larger
MPV changes were detected between PRE and POST in
the Elite group compared to the non-Elite (3.4 ± 2.6 %
vs. 1.4 ± 2.5; p< 0.05; Fig. 5a). Also, significant higher
increases in CMJ power were detected in the Elite group
Fig. 1 Changes in urine osmolality between PRE and POST time
points for each group (EUH, HYP and S-HYP). Data are presented as
mean ± SEM. *Significant difference respective to the PRE time
point.
a
significant difference when compared to EUH at PRE;
b
when
compared to HYP at PRE;
c
when compared to EUH at POST;
d
when
compared to HYP at POST
Fig 2 Relative changes in body mass for each group (EUH, HYP and S-
HYP). Data are presented as mean ± SEM. Significant differences
a
when
compared to EUH;
b
when compared to HYP
Fig. 3 Correlation between U
OSM
changes and body mass changes
between PRE and POST time points in the whole sample
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 5 of 9
compared to the non-Elite athletes (3.4 ± 4.7 % vs. 1.5 ±
4.1; p< 0.05; Fig. 5b).
Out of the 163 participants in this study, 102 (i.e., 63 %)
started the competition with a body mass above the
weight category they entered at weigh-in (i.e., 13–18 h
before competition). Thus, those 102 participants are sus-
pected of having undergone dehydration to cut weight. Of
these 102 athletes, 70 of them obtained a medal (i.e., Elite)
in the championship. This is, 69 % of all the hypohydrated
athletes at weigh-in were successful at competition.
Conversely, only an 11 % of the athletes obtaining a
medal did not enter a lower weight category at
weigh-in, and thus did not undergo dehydration. If
weigh-in had taken place right before competition, 89 %
of the Elite (medal winners) would not have entered the
weight category at which they competed. However, only
44 % of the non-Elite would not have entered the weight
category they ended up competing in.
Discussion
In this study we measured upper and lower body muscle
power and isometric strength in 163 Olympic weight-
class athletes (e.g. wrestling, boxing and taekwondo) at
the official weigh-in (PRE) and 13–18 h after (POST),
immediately prior to a National Championship competi-
tion. We found that based on urine osmolality, at weigh-
Fig. 4 Relative changes in (a), bench press mean propulsive velocity,
(b) countermovement jump power and (c) grip strength (between
PRE and POST time points for each group (EUH, HYP and S-HYP). Data
are presented as mean ± SEM.
a
Significantly different compared to
EUH.
b
Significantly different compared to HYP
Fig. 5 Relative changes in (a) bench press mean propulsive velocity
and (b) countermovement jump power between PRE and POST
testing for Elite and non-Elite groups. Data are presented as mean ±
SEM. *Significantly different when compared to Elite
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 6 of 9
in, 42 % of the athletes were moderately hypohydrated
(700–1080 mOsm · kg H
2
O
−1
; HYP), 42 % were severely
hypohydrated (1081–1500 mOsm · kg H
2
O
−1
; S-HYP)
and only 16 % were not hypohydrated (<700 mOsm · kg
H
2
O
−1
; EUH). In the hypohydrated groups (i.e., HYP
and S-HYP) 13–18 h after weigh-in, body mass was re-
covered by 1.2 and 3.1 %, respectively. This gain in body
mass in this relatively short period of time is attributable
mostly to body water restoration. This fast rehydration
did not increase isometric grip strength. However, lower
body (i.e., CMJ) and upper body (i.e., bench press)
muscle power increased in the group which was more
hypohydrated (i.e., S-HYP) compared to the other
groups. Thus, although severe dehydration permits
fighters to enter a lower weight category, it reduces their
neuromuscular performance. However, weight regain be-
tween weigh-in and the beginning of the competition
(i.e., 13–18 h rehydration) offsets at least part of muscle
function losses.
We observed that medal winners in the National
Championship ranked among the more hypohydrated
subjects based in urine osmolality at weigh-in (i.e., PRE).
However, urine osmolality at weight regain (i.e., POST)
was not different between the winners and the rest of
the athletes (907 vs. 888 mOsm · kg H
2
O
−1
). This sug-
gests that medal winners are able to dehydrate more
than their counterparts and recover more fluid during
those 13–18 h before competition. This allows them to
be placed in a lower weight category at weigh-in, while
relapsing to their habitual body mass in a few hours.
This denotes a special ability in the high level competi-
tors for losing and gaining body fluids. The relative
change in bench press MPV in medal winners was larger
than in the rest of the participants, which suggests that
their ability to recover body fluids allows them to also
rapidly recover their muscle power. Our data is in agree-
ment with a previous study on 159 varsity wrestlers [8]
reinforcing the belief that weight cutting and placement
in a lower weight category could be associated with
greater competition success.
Other authors have suggested the relationship between
an athlete’s ability to weight-cut and their success in
competition in combat sports. Horswill [2] pointed out
that successful USA collegiate wrestlers at their national
championship tended to lose more weight than those
not as successful. Wroble and Moxley [8] suggested that
wrestling below minimum wrestling weight is associated
with greater success in competition. Lastly, Artioli’s
group detected, in a descriptive study involving more
than 800 judo athletes, that the level of aggressiveness in
their weight loss behaviors (i.e., larger weight losses in
shorter time) increases in the Elite [27]. However, our
study is unique in explaining the association between
weight loss at weigh-in and competitive success the next
day. First, our measures of U
OSM
allows us to confirm
that in combat sport athletes, the loss of body
mass involves dehydration, since the gains in body
mass are tightly correlated with the reductions in
U
OSM
(r=0.504;p< 0.001; Fig. 3), a recognized marker of
hydration status. Secondly, our study suggests that muscle
power in upper and lower muscles is reduced mostly
when hypohydration is severe (i.e., S-HYP). Furthermore,
our data shows that muscle power can be recovered
(3-7 % in S-HYP) in the 13–18 h between weigh-in
and competition (Figs. 4 and 5). We are not able to
conclude if rehydration during those 13–18 h allowed
full or partial muscle power restoration because we
are lacking a basal measurement. However, the in-
creases were higher in the elite group since they were
more dehydrated at weigh-in. This suggests that al-
though hydration and likely muscle power were not
fully restored, entering a lower weight category com-
pensated for those effects.
The group of athletes we tested included 39 women
and 124 men of different competitive levels (National
and International), with a wide range of body mass (45.8
to 119.8 kg), fat free mass (71.1 % to 97.7 %) and thus
amount of muscle mass and potential strength. As a
consequence, within each hydration level group these
athletes present a disparity of neuromuscular perform-
ance in absolute terms for CMJ power, bench press
MPV and isometric grip strength. For instance, a body
mass gain between PRE and POST of 1000 gr in an indi-
vidual of 50 kg (2 % increment) will expectedly have lar-
ger physiological consequences than the same rise in an
individual of 100 kg (1 % increment). In the same way,
an isometric grip strength gain of 2 kg between PRE and
POST in an individual of 30 kg of maximum isometric
grip strength (6.6 % increment) will be more significant
than the same rise in an individual with a maximum
grip strength of 60 kg (3.3 % increment). In contrast,
a urine osmolality increment between the official
weigh-in and the beginning of the tournament of 150
mOsm · kg H
2
O
−1
has the same physiological effect,
and therefore will have the same significance, in an
individual of 50 kg, 70 kg or 90 kg of body mass.
Thus, body mass, hand grip, CMJ power and bench
press muscle contraction velocity changes between
PRE and POST trials were analyzed in relative terms
(i.e., percent changes), while urine osmolality values
were analyzed in absolute terms.
The effects of hypohydration on muscle performance
have been studied using different protocols and meas-
urement techniques. Studies vary in the percentage of
dehydration achieved from 1.7 % to 5.8 % of body mass
reduction [13, 16, 20, 21, 28]. Also, in the mode of dehy-
dration, with either thermally induced passive dehydra-
tion [29], exercise-induced active dehydration [20, 30] or
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 7 of 9
diuretic induced dehydration [28]. Additionally, studies
widely differ in the muscle performance tests used with
studies testing either 1 RM [16], local muscle endurance
[31], isometric strength [17, 20, 21, 31] or isokinetic
force [19, 20]. Recently, Judelson and co-workers [32]
reviewed the literature in this area and concluded that
dehydration ranged between 2.5–5.0 % of body mass
consistently attenuates strength by 2 % and power by ap-
proximately 3 %. The origin of these reductions has been
speculated to reside on alterations in cardiovascular,
metabolic or buffering functions [2]. Unfortunately, none
of these factors have been able to be related to the losses
in strength and power with hypohydration. Alternatively,
hypohydration may affect neuromuscular function [20,
32] although membrane excitability is not reduced by
dehydration [33]. In the present study we use a neuro-
muscular test in a real sports situation. Our subjects
were left to dehydrate using a technique of their choice
and their upper body neuromuscular performance was
tested before and after rehydration using a very reliable
technique [23]. We were able to discriminate a 1.5 % sig-
nificant increases in mean propulsive velocity (MPV)
due to the high reproducibility and sensitivity of this
technique [34].
Our neuromuscular bench press testing is highly
normalized and has high reproducibility [23] and
sensibility [34–36]. However, neuromuscular function
is influenced by circadian rhythm [34, 37]. We have
reported 5.6–8.6 % reductions in bench press muscle
power in the morning (8:00 h) in comparison to the
afternoon (i.e., 18:00 h; [34, 36, 37]). Thus, the lack
of increase in bench press muscle power in the group
that recovered 1.2 % of their body mass (i.e., HYP)
could be partially due to the fact that the test after
rehydration (POST) was conducted in the morning
(between 8:00 h and 10:00 h), while the hypohydrated
test (PRE) was conducted in the evening (between
16:00 h and 19:00 h). Likewise, the percentage increases in
neuromuscular performance found in S-HYP athletes (i.e.,
2.8–7.3 %) could have been larger if they had been tested at
thesametimeofday.Judgingfromurineosmolality,HYP
and S-HYP subjects did not return to a euhydrated condi-
tion after the 18–24 h. However, S-HYP subjects signifi-
cantly increased muscle power although they were still
moderately hypohydrated (urine osmolality 1000.4 ± 23.0
mOsm · kg H
2
O
−1
; Fig. 1). It is possible that full rehydration
would have resulted in larger gains in neuromuscular
performance.
Grip strength was not sensitive to weight regain (rehy-
dration) in our subjects. Isometric force has been previ-
ously evaluated in athletes prior and after dehydration
but the results are controversial. Maximal isometric
muscle strength is found to be either reduced [17] or
unchanged [18, 19], probably due to the poor reliability
of this measure (CV > 10 %). Furthermore, the effects of
hypohydration on the central or peripheral nervous sys-
tem is not evident when contraction time is not a limita-
tion for motor unit recruitment, as it is during isometric
contraction. Coinciding with our results, Judelson and
co-workers, reported reduced central drive with hypohy-
dration (reduced voluntary activation) however, isomet-
ric strength was unchanged [31].
Some authors sustain that the time allowed between
weigh-in and competition is enough to recover fluid and
energy substrates. Tarnopolsky et al. [38], observed that
the weight loss using energy and fluid restriction before
weigh-in results in a marked decrease in muscle glyco-
gen concentration which could affect high intensity an-
aerobic actions common in combat sports. However,
those reductions in muscle glycogen concentrations are
largely reversed during the 17 h period allowed between
weigh-in and the start of the competition [38]. Recent
reports sustain that the dehydration incurred at weigh-in
by combat sport athletes does not affect their combat
performance. Artioli and co-workers studied judo com-
bat athletes before and after rapid (5 to 7 days) weight
loss (i.e., 5 %) using a self-selected regime that included
voluntary dehydration. They found that weight loss did
not affect judo-related performance (i.e., 5 min simu-
lated combat) or anaerobic power during a Wingate test
(i.e., 30 s all-out effort; [39]). Rapid weight loss did not
affect performance in judo combat athletes that were
not used to weight-cut (non-weight cyclers) and thus
could not be attributable to adaptations to chronic
weight cycling [40]. Thus, it is possible that the increase
in muscle function that we found after 13–18 h of recov-
ery in the S-HYP group which showed a decline in
muscle power when hypohydrated at weigh-in (hypohy-
dration) may not influence combat performance.
Conclusions
In summary, our findings suggest that hypohydration is
highly prevalent (i.e., 84 %) among competitive combat
sports athletes, while 42 % of them undergo severe dehy-
dration at weigh-in. Furthermore, severe dehydration at
weigh-in (group S-HYP) seemed to lower neuromuscular
bench press muscle contraction velocity (7.3 ± 2.6 %)
and jumping power (2.8 ± 3.9 %) when compared to
values after 13–18 h of rest and rehydration. Conversely,
the neuromuscular performance impairment of severe
dehydration can be reversed with rehydration during the
few hours that elapse between weigh-in and competition.
Our experimental design precludes us from ascertaining
if this recovery of power is partial or full since we do not
have a euhydrated control situation to compare it to. Fi-
nally, our data suggest that most successful competitors
(medal winners in these National Championships)
undergo severe dehydration followed by weight regain
Pallarés et al. Journal of the International Society of Sports Nutrition (2016) 13:10 Page 8 of 9
without reaching full rehydration. Perhaps, the advan-
tage of competing in a weight category below the ath-
lete’s habitual weight, balances the negative effects of
competing somewhat hypohydrated.
Competing interests
The authors declare that they have no competing interests.
Authors’contributions
RMR, JGP, and AMA were involved with study design, subject recruitment,
scheduling and coordination, protocol setup and supervision, data
acquisition, data analysis and interpretation, and preparation of the
manuscript. RMN, ECS, and JMLG were involved in study design, data
interpretation, and preparation of the manuscript. All authors read and
approved the final manuscript.
Acknowledgements
The authors acknowledge the dedication, commitment, and professionalism
of athletes and coaches who took part in this investigation. The authors
report no conflicts of interest. The authors have no financial or personal
conflicts of interest to declare.
Author details
1
Human Performance and Sports Science Laboratory, University of Murcia,
Murcia, Spain.
2
Exercise Physiology Laboratory, University of Castilla-La
Mancha, Toledo, Spain.
Received: 29 September 2015 Accepted: 29 February 2016
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