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Short-Duration Beta-Alanine Supplementation Did Not Prevent the Detrimental Effects of an Intense Preparatory Period on Exercise Capacity in Top-Level Female Footballers

  • Brazilian National Football Confederation

Abstract and Figures

Purpose: High-intensity activity is an important aspect of football performance during competitive match play. The aim of this study was to investigate the effect of beta-alanine supplementation throughout a short-duration intense football-specific training period prior to an international competition on measures of high-intensity running performance. Methods: Twenty-four elite international U20 female footballers (age 18 ± 1 y, height 1.67 ± 0.07 m, body mass 62.7 ± 7.4 kg) volunteered to perform the YoYo Intermittent Recovery Test Level 1 (YoYo IR1), the Running Anaerobic Sprint Test (RAST) and a 20-m maximal sprint test on two separate occasions, separated by 3 weeks of training and supplementation. Participants were randomly assigned to receive either 6.4 g·day−1 sustained-release beta-alanine (BA, N = 12) or an equivalent dose of maltodextrin (placebo, PL, N = 12) throughout a 3-week standardized training camp. Results: There was a main effect of group (P = 0.05) and time (P = 0.004) on YoYo IR1; overall values were lower in PL and distance covered was lower post- vs. pre-supplementation. There was no group × time interaction (P = 0.07). There was an effect of sprint number for RAST, but no further main effects and there were no effect for the 20-m sprint. Conclusions: Top-level female footballers involved in this intense 3-week training period prior to a competition worsened their high-intensity intermittent exercise capacity, and this negative result was not attenuated by a short-duration BA supplementation protocol throughout the same period. Further work is necessary to elucidate whether adapted training protocols and BA dosing regimens could lead to better results.
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published: 21 April 2020
doi: 10.3389/fnut.2020.00043
Frontiers in Nutrition | 1April 2020 | Volume 7 | Article 43
Edited by:
David Christopher Nieman,
Appalachian State University,
United States
Reviewed by:
David Hooper,
Jacksonville University, United States
Sophie C. Killer,
English Institute of Sport,
United Kingdom
Bryan Saunders
Specialty section:
This article was submitted to
Sport and Exercise Nutrition,
a section of the journal
Frontiers in Nutrition
Received: 13 January 2020
Accepted: 20 March 2020
Published: 21 April 2020
Ribeiro R, Duarte B, Guedes da
Silva A, Ramos GP, Rossi Picanço A,
Penna EM, Coswig V, Barbalho M,
Gentil P, Gualano B and Saunders B
(2020) Short-Duration Beta-Alanine
Supplementation Did Not Prevent the
Detrimental Effects of an Intense
Preparatory Period on Exercise
Capacity in Top-Level Female
Footballers. Front. Nutr. 7:43.
doi: 10.3389/fnut.2020.00043
Short-Duration Beta-Alanine
Supplementation Did Not Prevent the
Detrimental Effects of an Intense
Preparatory Period on Exercise
Capacity in Top-Level Female
Rafael Ribeiro 1, Breno Duarte 1, André Guedes da Silva 1, Guilherme Passos Ramos 2,
Andreia Rossi Picanço 2, Eduardo Macedo Penna 3, Victor Coswig 3, Matheus Barbalho 4,
Paulo Gentil 4, Bruno Gualano 1and Bryan Saunders 1,5
1Applied Physiology and Nutrition Research Group, School of Physical Education and Sport, Rheumatology Division,
Faculdade de Medicina FMUSP, Universidade de São Paulo, São Paulo, Brazil, 2Confederação Brasileira de Futebol, Rio de
Janeiro, Brazil, 3Physical Education, Federal University of Pará – Campus Castanhal, Castanhal, Brazil, 4Physical Education
and Dance Institute, Federal University of Goiás, Goiânia, Brazil, 5Institute of Orthopaedics and Traumatology, Faculty of
Medicine FMUSP, University of São Paulo, São Paulo, Brazil
Purpose: High-intensity activity is an important aspect of football performance during
competitive match play. The aim of this study was to investigate the effect of beta-alanine
supplementation throughout a short-duration intense football-specific training period
prior to an international competition on measures of high-intensity running performance.
Methods: Twenty-four elite international U20 female footballers (age 18 ±1 y, height
1.67 ±0.07 m, body mass 62.7 ±7.4 kg) volunteered to perform the YoYo Intermittent
Recovery Test Level 1 (YoYo IR1), the Running Anaerobic Sprint Test (RAST) and a 20-m
maximal sprint test on two separate occasions, separated by 3 weeks of training and
supplementation. Participants were randomly assigned to receive either 6.4 g·day1
sustained-release beta-alanine (BA, N=12) or an equivalent dose of maltodextrin
(placebo, PL, N=12) throughout a 3-week standardized training camp.
Results: There was a main effect of group (P=0.05) and time (P=0.004) on YoYo
IR1; overall values were lower in PL and distance covered was lower post- vs. pre-
supplementation. There was no group ×time interaction (P=0.07). There was an effect
of sprint number for RAST, but no further main effects and there were no effect for the
20-m sprint.
Conclusions: Top-level female footballers involved in this intense 3-week training period
prior to a competition worsened their high-intensity intermittent exercise capacity, and
this negative result was not attenuated by a short-duration BA supplementation protocol
throughout the same period. Further work is necessary to elucidate whether adapted
training protocols and BA dosing regimens could lead to better results.
Keywords: football training, nutritional supplementation, YoYo intermittent recovery test, repeated sprints,
competition, fatigue, elite
Ribeiro et al. Short-Duration Beta-Alanine Supplementation Female Footballers
Football, also commonly termed as soccer, is the world’s most
popular sport, practiced by men and women all around the
world (1). The women’s game has seen a stark increase in
both popularity and professionalism over the past decade,
with research into the physiological demands of the women’s
game following a similar rise in popularity (2). The general
characteristics of women’s football demonstrate that match-
play is predominantly performed at low-intensity activities
interspersed by numerous high-intensity actions throughout
(2,3). Key moments that can affect the outcome of a game
generally occur at high-intensities. High-intensity efforts are
reduced during various phases of international matches and vary
according to position (4) and top-level women players have
been shown to perform more high-intensity running and sprints
during games than their less successful counterparts (5). High-
intensity activity, therefore, appears to be an important aspect of
football performance during competitive match play.
Several field tests are employed to evaluate the training
status of football players and are commonly used to predict
match performance and determine the effectiveness of a training
intervention. The YoYo Intermittent Recovery Tests (Level 1
[YoYo IR1] and 2 [YoYo IR2]) evaluate an individual’s capacity
to repeatedly perform and recover from intense exercise bouts,
and is applicable to team sports players due to the specificity of
the exercise undertaken (6). The Yo-Yo IR1 and IR2 have been
shown to correlate to various variables of match performance
and can be used as an indicator of the physical performance
of elite female players throughout competitive matches (7,8),
making them appropriate models to examine the effect of any
intervention designed to manipulate changes in performance
during team sports. In addition to differentiating between playing
standard, these tests can be used to monitor training adaptations,
seasonal variation and determine differences between playing
position [for review, see (9)]. The running anaerobic sprint test
(RAST) is another protocol that has been shown to be reliable
and valid to assess anaerobic power and is a good predictor of
short-distance running performances (10) while the 20-m sprint
test is a commonly used measure to assess team sport players (11).
Any changes in these performance measures may be reflective of
an enhanced capacity to improve in-match performance and thus
are useful tools to determine the efficacy of any intervention.
The preparation period prior to an international competition
is a delicate one in which fitness training must ensure a
maintenance and rebuilding process following an intense season
to ensure peak condition for the subsequent intense period
of matches (12). During this phase there may also be an
additional focus on technical and tactical preparation as opposed
to intense physical conditioning (13).This is commonly referred
to as the taper, which involves reducing the training loads
from a previously intense program to optimise recovery and
maximise performance (14,15). Athletes commonly employ
supplementation methods to enhance any adaptations from
training routines. Beta-alanine is an amino acid that is ingested
over several weeks to increase muscle carnosine content (16)
and improve exercise capacity and performance (17). It is
considered an effective ergogenic aid by the International
Olympic Committee (18), although the effects of beta-alanine
on football-specific protocols is unclear and contradictory.
Beta-alanine has previously improved YoYo IR2 performance
in amateur male footballers throughout a competitive season
(19), although YoYo IR1 was not improved in young elite
male basketball players (20). Evidence to support beta-alanine
supplementation during shorter-duration repeated sprints is
distinctly lacking (2123) although supplementation alongside
plyometric training did lead to greater improvements in RAST
than training alone in female soccer players (11). This suggests
that the combination of training and beta-alanine may be
additive, something previously demonstrated with cycling sprint
training (24), although no study to date has investigated the
combined effect of a football-specific training period alongside
beta-alanine supplementation on football-specific performance
in females.
The aim of this study was to investigate the effect of beta-
alanine supplementation throughout a short-duration intense
football-specific training period prior to an international
competition on measures of high-intensity running performance.
We hypothesised that supplementation would lead to greater
improvements in exercise measures than any seen with
training alone.
Twenty-four elite international under-20 (U20) female
footballers (age 18 ±1 y, height 1.67 ±0.07 m, body mass
62.7 ±7.4 kg) from different clubs competing in the elite
divisions of the Brazilian football pyramid that were part of the
national Brazilian team preparing for the South American U20
Women’s Championship, volunteered for the study and were
randomly assigned to receive either beta-alanine (BA, N=12)
or placebo (PL, N=12). Subjects had not taken any creatine
supplement in the 3 months prior to the study and had not taken
BA for at least 6 months. None of the subjects were vegetarian
and, therefore, would have encountered small amounts of
beta-alanine in their diet from the hydrolysis of carnosine and
its methyl derivatives in meat. The study was approved by the
institution’s Ethical Advisory Committee.
Experimental Design
All athletes in this study routinely performed the exercise
protocols as part of standard fitness testing throughout their
respective seasons. Participants performed the YoYo IR1, RAST,
and 20-m sprint test on two separate occasions, separated by
3 weeks of training and supplementation. The exercise tests
were performed in a standardized order: Sprint Test and the
YoYo IR1 in the morning and the RAST test in the evening.
All players performed the same 3-week standardized training
program, which consisted of 1 to 2 training sessions per day and
received 5 meals per day at standardized timepoints. Sleeping
and waking times during the training period were controlled and
identical for all athletes. Training and diet, including caffeine
consumption, in the 24 h period prior to the first main exercise
Frontiers in Nutrition | 2April 2020 | Volume 7 | Article 43
Ribeiro et al. Short-Duration Beta-Alanine Supplementation Female Footballers
session were standardized and the athletes repeated this prior to
the second main session.
Supplement group allocation was conducted in blocks with
groups being equalized according to performance in the
YoYo IR1. Throughout the same 3-week period, participants
were supplemented with either 6.4 g·day1of beta-alanine
(CarnoSynTM, NAI, USA) or placebo (maltodextrin; NAI, USA)
in sustained-release tablets. The dosing regimen consisted of
two 800 mg BA or PL tablets ingested four times per day (7
AM/12 PM/5 PM/10 PM). Participants ingested the supplements
alongside their standardized meals and a final dose before
bed, ensuring all had 100% compliance to the supplementation
regimen. No participant in either group reported any symptoms
of paraesthesia throughout supplementation.
Experimental Procedures
YoYo Intermittent Recovery Test – Level 1
The YoYo IR1 consists of repeated 2 ×20 m runs between
markers at progressively increasing speeds dictated by an audio
signal. At the end of each 2 ×20 m bout, individuals performed
10 s of active recovery between consisting of a 10 m (2 ×5 m)
walk. The test ended if the player failed to reach the finish line
within the given time frame on two consecutive occasions or if
the player felt unable to continue (volitional exhaustion). The
total distance covered (m) during the test was recorded as the
outcome measure.
Running Anaerobic Sprint Test (RAST) and 20-m
The RAST consisted of seven 20-m maximal sprints with a
passive 10 s recovery period between each sprint; the start of each
sprint was indicated by a beep from the photocell equipment
(CEFISE standard photocells, Brazil) which measured run time
for every individual sprint. The photocells were connected to
a computer with specific software (CEFISE, Brasil) for speed
analysis. Outcome measures were sprint time of each sprint
(s), total sprint time (s), mean, maximum and minimum
power output (W) [calculated as Power =(Body Mass ×
Distance2)/Time3] and fatigue index (FI, %) [calculated as FI
=(peak power - minimum power/peak power) ×100)] (10).
Participants also performed 3 separate attempts of a maximum
20 m sprint test, with 5 min passive recovery between efforts. To
start the sprint, the volunteer was positioned 1 m behind the
first photocell to prevent premature activation of the timer. The
timing of the start of each maximal sprint was determined by
the athlete.
Data Analysis
Data were analysed using the SAS statistical package (SAS R
University Edition, SAS Institute Inc., USA), and are presented
as mean ±1SD unless stated. Exercise data were analysed using
mixed model analysis with individuals assumed as a random
factor and supplementation (2 levels; BA and PL) and time (2
levels; Day 0 and 20) assumed as fixed factors. Repeated sprints
during the RAST were analysed using mixed model analysis with
individuals assumed as a random factor and supplementation
(2 levels; BA and PL), time (2 levels; Day 0 and 20) and sprint
number (7 levels; 0-7) assumed as fixed factors. Tukey–Kramer
FIGURE 1 | Distance covered during the YoYo IR 1 test in the beta-alanine
(BA) and placebo (PL) groups pre- and post-supplementation. *P=0.004.
Effect of time.
adjustments were performed when a significant F value was
obtained, and the significance level was set a priori at P0.05.
Individual responses for the YoYo IR1 were calculated according
to time-to-completion using the spreadsheet of Swinton et al. (25)
using 90% confidence intervals, a typical error calculated from
reproducibility data (26) and a smallest worthwhile change of 0.2
×the standard deviation of the control session (27). Due to issues
unrelated to the intervention (due to minor illness or injury, the
coaches instructed the athletes not to complete all protocols as
a precautionary measure), complete data for the YoYo IR1 was
obtained for 20 athletes (BA =10, PL =10) and 22 athletes
completed the 20-m sprint (BA =11, PL =11); all athletes
completed the RAST pre- and post-supplementation.
YoYo IR1
YoYo performance was not significantly different between groups
at baseline (BA: 644 ±114 m, PL: 513 ±125 m; P=0.07),
although this almost reached statistical significance. This might
be due to missing data (2 individuals from BA and 2 from
PL). There was a main effect of group (P=0.046), with lower
overall values in the PL vs. BA group, and time (P=0.004);
distance covered was lower post- versus per-supplementation
(7.4 ±14.4%). The group ×time interaction did not reach
statistical significance (P=0.07; Figure 1). Individual data
analysis revealed that no individuals in either group improved
performance above the smallest worthwhile change during
the YoYo IR1, although two athletes in BA and one in PL
worsened performance.
RAST and 20 m Sprint
There was no effect of group (P=0.67) or time (P=0.45) for
sprint times during the RAST, but there was an effect of sprint
number (P<0.0001), reflecting an increase in time to complete
each sprint with increasing sprint number (Table 1). There were
Frontiers in Nutrition | 3April 2020 | Volume 7 | Article 43
Ribeiro et al. Short-Duration Beta-Alanine Supplementation Female Footballers
TABLE 1 | Sprint times (s) during the RAST for the beta-alanine (BA) and placebo
(PL) groups pre- and post-supplementation.
Pre Post Pre Post
Sprint 1 (s) 3.6 ±0.1 3.5 ±0.1 3.5 ±0.1 3.6 ±0.1
Sprint 2 (s) 3.6 ±0.2 3.6 ±0.1 3.6 ±0.1 3.6 ±0.1
Sprint 3 (s) 3.7 ±0.1* 3.7 ±0.2* 3.6 ±0.1* 3.7 ±0.2*
Sprint 4 (s) 3.8 ±0.2* 3.8 ±0.2* 3.7 ±0.1* 3.7 ±0.2*
Sprint 5 (s) 3.8 ±0.1* 3.8 ±0.2* 3.8 ±0.1* 3.8 ±0.2*
Sprint 6 (s) 3.9 ±0.2* 3.9 ±0.2* 3.8 ±0.1* 3.9 ±0.2*
Sprint 7 (s) 3.9 ±0.1* 3.9 ±0.2* 3.9 ±0.1* 3.9 ±0.1*
Total sprint time (s) 26.1 ±1.0 26.2 ±1.0 26.0 ±0.6 26.0 ±1.0
20-m sprint 3.5 ±0.1 3.5 ±0.2 3.5 ±0.1 3.4 ±0.1
P<0.0001 Effect of sprint, *indicates a significant difference from Sprint 1.
no group ×time ×sprint interaction effects for sprint times (P
=0.96). There were no group, time or group ×time interactions
for total time, maximum, mean and minimum power and fatigue
index during the RAST (all P>0.05) (Figure 2). There was no
effect of group (P=0.91), time (P=0.50) or group ×time
interaction (P=0.25) for the 20-m sprint test.
This study aimed to investigate the effect of BA supplementation
in high-level Brazilian female soccer players during a three-
week preparatory training period. The main findings showed that
responses to BA supplementation were not different from those
obtained with placebo and were unable to avoid decreases in
performance during the YoYo IR1, which likely occurred due to
high workloads imposed in this preparatory period. There were
no changes in repeated or maximal sprint performance.
The training load employed with these athletes resulted in a
reduced exercise capacity during the YoYo IR1 (7.4%). Prior to
major events, such as an international tournament, it is common
to taper, namely reducing the training load from a previously
intense program in order to optimise gains and recovery and
maximise subsequent performance (14,15). Our data suggest
that, not only was the training intervention too intense in nature
to illicit improvements in exercise capacity, it actually worsened
performance which is contrary to the aims of the training.
Previous data from an under-20 female football team preparing
for the World Cup showed a progressive improvement in YoYo
IR1 performance leading up to competition (Tunstall H, personal
communication in (6)), although the authors suggest this was
reflective of a more focused fitness training schedule and the low
starting fitness levels of these female players. In the current study,
our athletes all plied their trade for top-level national sides, and
most were regular starters for their respective teams. It is possible
that a long grueling season took its toll on the players, and that
performance was a result of accumulated fatigue over the season
and would have reduced over this three-week period regardless
of the intense training. In fact, YoYo IR1 performance of these
FIGURE 2 | Sprint performance during the RAST for the beta-alanine (A) and
placebo (B) groups pre- (clear bars) and post- (striped bars) supplementation.
*P<0.0001. Effect of sprint number.
athletes prior to the training and supplementation intervention
was lower than that shown previously in elite female footballers
(7,9), which provides support for this theory.
Short-term BA supplementation (3 weeks) was unable
to attenuate this training-associated decline in YoYo IR1
performance. The lack of an effect shown here is line with
previous research showing no changes in YoYo IR1 in young elite
male basketball players with BA supplementation (20), although
BA did improve YoYo IR2 (19) in amateur male footballers. The
YoYo IR2 is initiated at a higher intensity than the YoYo IR1,
with a higher contribution from anaerobic glycolytic pathways
increasing the contribution of buffering capacity to performance
(9), making it more susceptible to improvements with BA. It is
also possible that the relatively short loading period in this study
did not meet the threshold necessary for a sufficient increase
in muscle carnosine to elicit performance improvements. Smith
et al. (28) showed similar improvement in cycling capacity
following 3 weeks of high-intensity interval training with both
BA and PL, but greater improvements from weeks 3–6 were
shown with BA. It is currently unknown what the minimal
necessary increase in muscle carnosine is to elicit a performance
improvement (29) and any definitive conclusions here are not
Frontiers in Nutrition | 4April 2020 | Volume 7 | Article 43
Ribeiro et al. Short-Duration Beta-Alanine Supplementation Female Footballers
possible due to the lack of muscle carnosine content analysis in
the current study. Had the athletes commenced supplementation
prior to the training phase, thus ensuring increased muscle
carnosine content prior to the intense training period, it is
possible that results may have been different. However, we were
unable to enforce the supplementation protocol prior to the
international period during which we had access to the players,
a potential consequence of working with elite club players on
international duty. As it stands, short-term BA supplementation
was unable to attenuate the decline in YoYo IR1 performance
following the training period in this study.
Neither training nor supplementation led to changes in
repeated sprint ability or sprint performance. These data are
in line with previous studies showing no effect of BA on
short-duration repeated sprints in team sports players (21,
22). However, previous research in female football players
has shown BA supplementation to improve mean power
output during repeated 30-s Wingate sprints (30) and induce
greater improvements in repeated-sprint tests when combined
with plyometric training compared to training alone (11).
It is possible that the highly trained nature of our athletes
contributed to these results, since meta-analytical data has
shown well-trained individuals to achieve smaller performance
gains with supplementation than non-trained individuals (17).
The aforementioned studies recruited university level (30) and
amateur (11) players, while we employed elite youth players. It is
also important to again emphasise that the lack of any changes
in these tests may similarly be due to the intense nature of the
training program, inhibiting any potential adaptations with or
without supplementation.
One of the strengths of this study is that it was a real-
world intervention in which we implemented a double-blind
placebo-controlled supplementation protocol in top-level female
athletes who were part of a competitive international set-up
performing their normal pre-competition training program. The
standardized pre-tournament training camp provided a unique
environment that required all athletes to undergo identical daily
routines such as training, nutritional intake and sleep, thus
removing several variables which could contribute to individual
variability. Indeed, our data showed striking consistency with all
but one individual in BA showing a reduction in distance covered
during the YoYo IR1, while six athletes in PL also covered less
distance; however, statistical analysis revealed that only two in BA
and one in PL could be considered to have worsened performance
with >90% certainty (25). The controlled nature of this study has
great practical applicability to similar athletes undergoing these
types of intervention by showing BA to be ineffective during such
a short and intense training period. However, alternative methods
might be implemented, such as lighter training loads and earlier
implementation of the supplementation regime, which might
lead to different results. Indeed, this study also highlights the
delicate nature of working with an international team since we
could not make any changes to their usual routines until their
individual seasons with their respective national clubs had ended.
Intense preparatory training periods prior to international
competitions may place unnecessary strain on top-level
footballers following a grueling season. Our data suggest
that international teams may inadvertently overload
their players leading to a reduced high-intensity exercise
capacity in these players. Reduced exercise capacity was
not counteracted by short-duration BA supplementation,
although it is possible that the supplementation protocol
was sub-optimal. Perhaps more communication between
clubs and international teams may facilitate this process and
avoid overreaching or overtraining, while prior initiation
of the supplementation protocol would further benefit any
potential adaptation.
Top-level female footballers involved in this intense 3-week
training period prior to a competition worsened their high-
intensity intermittent exercise capacity, and this negative result
was not attenuated by a short-duration BA supplementation
protocol throughout the same period. Further work is necessary
to elucidate whether adapted training protocols and BA dosing
regimens could lead to better results.
The datasets generated for this study are available on request to
the corresponding author.
The studies involving human participants were reviewed and
approved by University of São Paulo. The patients/participants
provided their written informed consent to participate in
this study.
GR, AR, EP, VC, MB, PG, BG, and BS contributed to the
conception and design of the study. RR, EP, and BS organized the
database and performed the statistical analysis. RR, BD, AG, EP,
and BS wrote the first draft of the manuscript. GR, AR, VC, MB,
PG, and BG contributed to the subsequent versions. All authors
contributed to manuscript revision, and read and approved the
final submitted version.
No specific funding was received for this investigation. BD
(2019/06140-5) and BS (2016/50438-0 and 2017/04973-4) have
been financially supported by Fundação de Amparo à Pesquisa
do Estado de São Paulo.
Frontiers in Nutrition | 5April 2020 | Volume 7 | Article 43
Ribeiro et al. Short-Duration Beta-Alanine Supplementation Female Footballers
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Conflict of Interest: BS has previously received financial support from Natural
Alternatives International (NAI), a company that produces BA, to undertake a
study unrelated to this one. NAI has also provided BA supplements free of charge
for this and further experimental investigations and supported open access page
charges for numerous publications involving the authors. NAI have not had any
input (financial, intellectual, or otherwise) into this original investigation.
The remaining authors declare that the research was conducted in the absence of
any commercial or financial relationships that could be construed as a potential
conflict of interest.
Copyright © 2020 Ribeiro, Duarte, Guedes da Silva, Ramos, Rossi Picanço, Penna,
Coswig, Barbalho, Gentil, Gualano and Saunders. This is an open-access article
distributed under the terms of the Creative Commons Attribution License (CC BY).
The use, distribution or reproduction in other forums is permitted, provided the
original author(s) and the copyright owner(s) are credited and that the original
publication in this journal is cited, in accordance with accepted academic practice.
No use, distribution or reproduction is permitted which does not comply with these
Frontiers in Nutrition | 6April 2020 | Volume 7 | Article 43
... Regarding the EAs used to enhance performance, CAF was used alone in 18 studies, (41.9%) [10,29,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54], combined with BJ in 2 articles [55,56], and with taurine (TAU) [57] and sodium phosphate (SP) [58] in another 2 studies. BA was presented alone in five studies [59][60][61][62][63] and combined with CRE in one study [64]. CRE was utilized in three studies [65][66][67]. ...
... Sprint capacity was assessed in six studies [29,52,58,63,73,75], with a total of k = 8 variables included in the analysis. The observed SMD presented values between −0.62 and 0.67, with the majority of estimates being positive (88%). ...
... Thus, even though the average outcome is taken to be positive, in some studies the true outcome may in fact be negative. The studentized residuals revealed that one variable (Ribeiro, 20 m-BA) [63] may be a potential outlier in the context of this model due to a value higher than ± 2.73. In addition, based on the Cook's distances, this variable could be considered to be overly influential ( Figure 5). ...
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Most intervention studies investigating the effects of ergogenic aids (EAs) on sports performance have been carried out in the male population. Thus, the aim of this systematic review and meta-analysis was to summarize the effects in the existing literature of EAs used by female athletes on performance. A literature research was conducted, and a descriptive analysis of the articles included in the systematic review was carried out. Meta-analyses could be performed on 32 of the included articles, evaluating performance in strength, sprint, and cardiovascular capacity. A random-effects model and the standardized mean differences (SMD) ± 95% confidence intervals (CI) were reported. The results showed that caffeine helped to improve jumping performance, isometric strength values, and the number of repetitions until failure. Caffeine and sodium phosphate helped to improve sprint performance. Aerobic tests could be improved with the use of taurine, caffeine, and beta-alanine. No conclusive effects of beetroot juice, polyphenols, or creatine in improving aerobic performance were shown. In terms of anaerobic variables, both caffeine and sodium phosphate could help to improve repeated sprint ability. More studies are needed in female athletes that measure the effects of different EAs on sports performance, such as beetroot juice, beta-alanine or sodium phosphate, as the studies to date are scarce and there are many types of EA that need to be further considered in this population, such as creatine and taurine.
... In addition to the main analysis, two subgroup analyses were also performed. In one subgroup analysis, data were analyzed after excluding one study [17] that used a 3-week supplementation protocol, which is shorter than other studies, as they used 6-12 weeks of supplementation. In another subgroup analysis, data were analyzed after excluding two studies that used the intermittent recovery level 1 version of the Yo-Yo test, as it has been suggested that greater effects of beta-alanine may be observed in the level 2 version [17,18]. ...
... In one subgroup analysis, data were analyzed after excluding one study [17] that used a 3-week supplementation protocol, which is shorter than other studies, as they used 6-12 weeks of supplementation. In another subgroup analysis, data were analyzed after excluding two studies that used the intermittent recovery level 1 version of the Yo-Yo test, as it has been suggested that greater effects of beta-alanine may be observed in the level 2 version [17,18]. SMDs were interpreted as: "trivial" (<0.20), "small" (0.20-0.39), "medium" (0.40-0.59), "large" (0.60-0.80), and "very large" (>0.80). ...
... There was a total of 226 results across the primary and secondary searches. Out of this pool of references, ten full-text papers were read, and five studies [12,13,[17][18][19] with a total of 10 groups satisfied the outlined inclusion criteria (Fig. 1). ...
Objective: The aim of this meta-analysis was to explore the effects of beta-alanine supplementation on Yo-Yo test performance. Methods: Nine databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses were conducted to explore the effects of beta-alanine supplementation duration on Yo-Yo test performance, and the effects of beta-alanine supplementation on performance only in Yo-Yo level 2 test variants. Results: Ten study groups were included in the meta-analysis. All studies included athletes as study participants. When considering all available studies, there was no significant difference between the placebo/control and beta-alanine groups (SMD: 0.68; 95% confidence interval [CI]: –0.30, 1.67). When considering only the studies that used supplementation protocols lasting between 6 and 12 weeks, there was a significant ergogenic effect of beta-alanine (SMD: 1.02; 95% CI: 0.01, 2.05). When considering only the studies that used the level 2 variants of the Yo-Yo test, there was a significant ergogenic effect of beta-alanine (SMD: 1.41; 95% CI: 0.35, 2.48). Conclusions: This meta-analysis found that beta-alanine is ergogenic for Yo-Yo test performance in athletes when the supplementation protocol lasts between 6 and 12 weeks and when using the level 2 variants of the Yo-Yo test.
... Considering the effective strategies of beta-alanine supplementation (4.8-6.4 g/day) in previous studies, the participants were instructed to consume 6.4 g/day of beta-alanine or maltodextrin supplements for eight weeks [25]. A capsule with 100% purity was provided for consumption. ...
... The results were consistent with the results of Ribeiro et al. (2020), who examined the effect of β-alanine supplementation on the performance of elite female soccer players. Ribeiro et al. showed that β-alanine supplementation increases the aerobic capacity measured in the RAST test [25]. ...
Full-text available
The purpose of this study was to evaluate the effect of 8-week β-alanine supplementation on C-Reactive Protein (CRP), interleukin-6 (IL-6), body composition, and bio-motor abilities in elite male basketball players. Twenty male basketball players (age: 23 + 0.6 years; body mass: 78.3 + 4.8 kg; height:185.3 + 5.4 cm, %BF, 15.2 ± 4.8) volunteered to participate in this study. They were divided into a β-alanine group (BG, N = 10) and a placebo group (PG, N = 10). All players were preparing for university competitions and had played for over five years. Players used 6.4 g/d of β-alanine in BG and maltodextrin in PG. The participants were involved in regular basketball training three months before the study. CRP, IL-6, body composition parameters, and bio-motor abilities were measured before starting the exercises and after completing the eight-week training period. The research findings showed a significant decrease in CRP and IL-6 and an increase in anaerobic peak power between the pre-test and post-test, as well as between BG and PG groups (p < 0.05). Although the other measured factors were a relative improvement compared to the pre-test and also compared to PG, these changes were not statistically significant (p < 0.05). Eight weeks of β-alanine supplementation ameliorated increases in IL-6 and CRP associated with in-season physical stressors in collegiate basketball players. These changes in pro-inflammatory cytokines suggest that β-alanine supplementation may be a useful nutritional strategy for immune regulation and can also improve anaerobic performance compared to PG.
... Overreaching is common at various points during the season in competitive cyclists, in response to increased volumes of training or competition [28,29] which ultimately reduces performance capacity [30]. To the best of our knowledge, only one study tested short-duration β-ala on males during an intensive training camp (last 9 days, 135 g of β-ala along 30 days) which did not improve anaerobic cycling capacity (Wingate test), but fatigue feelings [31], in line with another study on females which did not mitigate a reduction in high-intensity intermittent exercise capacity (YoYo and sprint test) during this preparatory period [32]. Both studies, together with this study, tested short-duration β-ala to help maintain performance when athletes are subject to a highly demanding physiological load, as is the case in intensive training camps or consecutive races during a professional athlete season. ...
... However, the buffering capacity of muscles did not change in these studies in spite of an increased muscle carnosine, suggesting an improved muscle force in shortduration high-intensity movements by acting on neuromuscular fatigue. In the current study, as the training week progressed, cyclists probably accumulated tiredness and fatigue characteristic of these intensive training camps [30,32], and β-ala helped to maintain mean power due to a preservation of the muscle buffering systems, action on central fatigue, or a combination of both. Recent studies in elite endurance athletes, sprinters and combat sports, suggest metabolic adaptation benefits (lower ammonia concentrations after exercise) during training periods [37,38] which may be an additional benefit of short-duration high-dose β-ala in lack of a visible performance improvement, in addition to a performance benefit. ...
Full-text available
Supplementation with β-alanine is becoming a common practice in high-performance athletes. The purpose of the present study was to investigate the effects of a one-week high-dose β-alanine loading phase employing a sustained-release powder on preserving the time-trial performance capacity of world tour cyclists during overreaching training. Per day, 20 g of sustained-release β-alanine was administered during one week (7 days) of intensive team training camp in a randomised balanced placebo-controlled parallel trial design, with six participants in each β-alanine (BA) or placebo (PLA) group. A 10-min time trial (10′ TT) was carried out to analyse performance and biochemical variables. Anthropometry, paresthesia, and adverse event data were also collected. Power-based relative training load was quantified. Compared to placebo, the BA improved mean power (6.21%, 37.23 W; 95% CI: 3.98–70.48 W, p = 0.046), distance travelled (2.16%, p = 0.046) and total work (4.85%, p = 0.046) without differences in cadence (p = 0.506) or RPE. Lactate (p = 0.036) and anion gap (p = 0.047) were also higher in the BA group, without differences in pH or Bicarbonate. High daily and single doses were well tolerated. One-week high-dose β-alanine loading with a sustained-release powder blend can help attenuate 10′ TT performance losses of world tour cyclists due to intensive training.
... Unfortunately, the effects of BA on football specific protocols are unclear and contradictory. In international youth female footballers, BA supplementation did not attenuate a drop in exercise intensity over an intense period of training (Ribeiro et al., 2020). Previous research in elite female soccer players found that a combination of BA and plyometric training compared to plyometric training alone did improve a running aerobic sprint test (Rosas et al., 2017). ...
Full-text available
The physical demands of professional female football have intensified in recent years. Supplements are only advised in addition to a healthy, balanced diet, but may warrant a greater prevalence in the professional game to support well-being, recovery, and performance. Supplements used by players should be safe, legal, and scientifically proven to be effective. An individual approach should be taken to using supplements dependant on the needs and goals of the player. Female players should aim to improve the frequency of protein intake throughout the day, whilst tailoring doses to individual body mass. Vitamin D supplementation is vital throughout the winter months in countries with limited sun exposure, however doses should be administered based on individual blood test results. Iron is likely to be important to the well-being of female athletes throughout the season, in particular during the menses. Omega-3 and collagen may be of greater benefit to female than male athletes during recovery from soft tissue injury, whilst probiotics and creatine are beneficial throughout the season for reducing risk of illness and optimising recovery, respectively. Ergogenic supplements for football include beta-alanine, nitrate and caffeine. Caution should be taken with caffeine use due to the varying tolerance of difference athletes and sleep impairments that can follow.
... Likewise, the daily intake of 2.4 g of β-alanine for 4 weeks resulted in a significant improvement in mean power during the Wingate anaerobic test among female footballers (Rodríguez Rodríguez et al., 2014). Otherwise, a 3-week clinical trial on female footballers showed that the administration of 6.4 g of β-alanine had no effect on sprint times during the RAST (Ribeiro et al., 2020). Likewise, in another study, no significant improvement in Wingate anaerobic power test and fatigue rate in 200-yd shuttle runs was observed with supplementation of 4.5 g β-alanine during 4 weeks in football players (Hoffman et al., 2008). ...
Full-text available
Background There are growing interests in using dietary supplements to improve athletic performance. This study aimed to evaluate the effect of the food ration bar enriched with β-alanine, L-arginine, and Nigella sativa on athletic performance and inflammation following intense military training. Methods This double-blind, randomized, controlled clinical trial was conducted on 54 new cadets. Eligible participants were randomly assigned in a 1:1 ratio to receive food ration bars enriched with arginine (2 g/day), β-alanine (2 g/day), and Nigella sativa (2 g/day) or nonenriched food ration bars during a 2-week military training. Aerobic and anaerobic performances were evaluated by the Cooper and RAST tests, respectively. Results A significant increase in anaerobic powers (min, mean, and max) and a significant reduction in fatigue index were observed in the intervention group as compared to the control group, even after the adjustment for confounding factors. Also, increased levels of hs-CRP and TNF-α following military training were significantly lower in the intervention group as compared to the control group (hs-CRP: 0.55 ± 0.1 versus 2.43 ± 0.1 mg/L; p-value: 0.01; TNF-α: 0.12 ± 0.04 versus 0.62 ± 0.04 pg/ml; p-value: 0.03). No significant changes were observed in VO2 max in both groups. Conclusions Our results showed that the combination of β-alanine, L-arginine, and Nigella sativa can improve anaerobic performance and reduce inflammation following intense physical activities. Further studies with long-term duration are needed to confirm the cumulative/synergic effects of these ingredients in trained and nontrained subjects.
Beta-alanine, caffeine, and nitrate are dietary supplements generally recognized by the sport and exercise science community as evidence-based ergogenic performance aids. Evidence supporting the efficacy of these supplements, however, is greatly skewed due to research being conducted primarily in men. The physiological differences between men and women, most notably in sex hormones and menstrual cycle fluctuations, make generalizing male data to the female athlete inappropriate, and potentially harmful to women. This narrative review outlines the studies conducted in women regarding the efficacy of beta-alanine, caffeine, and nitrate supplementation for performance enhancement. Only nine studies on beta-alanine, 15 on caffeine, and 10 on nitrate in healthy women under the age of 40 years conducted in normoxia conditions were identified as relevant to this research question. Evidence suggests that beta-alanine may lower the rate of perceived exertion and extend training bouts in women, leading to greater functional adaptations. Studies of caffeine in women suggest the physiological responder status and caffeine habituation may contribute to caffeine’s efficacy, with a potential plateau in the dose–response relationship of performance enhancement. Nitrate appears to vary in influence based on activity type and primary muscle group examined. However, the results summarized in the limited literature for each of these three supplements provide no consensus on dosage, timing, or efficacy for women. Furthermore, the literature lacks considerations for hormonal status and its role in metabolism. This gap in sex-based knowledge necessitates further research on these ergogenic supplements in women with greater considerations for the effects of hormonal status.
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Beta-alanine (BA) supplementation increases muscle carnosine content (MCarn), and is ergogenic in many situations. Currently, many questions on the nature of the Mcarn response to supplementation are open, and the response to these has considerable potential to enhance the efficacy and applications of this supplementation strategy. Objective To conduct a Bayesian analysis of available data on the Mcarn response to BA supplementation. Methods A systematic review with meta-analysis of individual and published aggregate data using a dose response (Emax) model was conducted. The protocol was designed according to PRISMA guidelines. A three-step screening strategy was undertaken to identify studies that measured the Mcarn response to BA supplementation. In addition, individual data from 5 separate studies conducted in the authors’ laboratory were analysed. Data were extracted from all controlled and uncontrolled supplementation studies conducted on healthy humans. Meta-regression was used to consider the influence of potential moderators (including dose, sex, age, baseline Mcarn and analysis method used) on the primary outcome. Results and Conclusion The Emax model indicated that human skeletal muscle has large capacity for non-linear Mcarn accumulation, and that commonly used BA supplementation protocols may not come close to saturating muscle carnosine content. Neither baseline values, nor sex, appear to influence subsequent response to supplementation. Analysis of individual data indicated that Mcarn is relatively stable in the absence of intervention, and effectually all participants respond to BA supplementation (99.3% response [95%CrI: 96.2 – 100]).
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Background: Although Yo-Yo intermittent tests are frequently used in a variety of sports and research studies to determine physical fitness, no structured reference exists for comparison and rating of test results. This systematic review of the most common Yo-Yo tests aimed to provide reference values for test results by statistical aggregation of published data. Methods: A systematic literature search for articles published until August 2017 was performed in MEDLINE, Web of Science, SPORTDiscus and Google Scholar. Original reports on healthy females and males ≥16 years were eligible for the analysis. Sub-maximal test versions and the Yo-Yo Intermittent Recovery Level 1 Children's test (YYIR1C) were not included. Results: 248 studies with 9,440 participants were included in the structured analysis. The Yo-Yo test types most frequently used were the Yo-Yo Intermittent Recovery Level 1 (YYIR1, 57.7%), the Yo-Yo Intermittent Recovery Level 2 (YYIR2, 28.0%), the Yo-Yo Intermittent Endurance Level 2 (YYIE2, 11.4%), and the Yo-Yo Intermittent Endurance Level 1 (YYIE1, 2.9%) test. For each separate test, reference values (global means and percentiles) for sports at different levels and both genders were calculated. Conclusions: Our analysis provides evidence that Yo-Yo intermittent tests reference values differ with respect to the type and level of sport performed.The presented results may be used by practitioners, trainers and athletes to rate Yo-Yo intermittent test performance levels and monitor training effects.
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The concept of personalised nutrition and exercise prescription represents a topical and exciting progression for the discipline given the large inter-individual variability that exists in response to virtually all performance and health related interventions. Appropriate interpretation of intervention-based data from an individual or group of individuals requires practitioners and researchers to consider a range of concepts including the confounding influence of measurement error and biological variability. In addition, the means to quantify likely statistical and practical improvements are facilitated by concepts such as confidence intervals (CIs) and smallest worthwhile change (SWC). The purpose of this review is to provide accessible and applicable recommendations for practitioners and researchers that interpret, and report personalised data. To achieve this, the review is structured in three sections that progressively develop a statistical framework. Section 1 explores fundamental concepts related to measurement error and describes how typical error and CIs can be used to express uncertainty in baseline measurements. Section 2 builds upon these concepts and demonstrates how CIs can be combined with the concept of SWC to assess whether meaningful improvements occur post-intervention. Finally, Section 3 introduces the concept of biological variability and discusses the subsequent challenges in identifying individual response and non-response to an intervention. Worked numerical examples and interactive supplementary material are incorporated to solidify concepts and assist with implementation in practice.
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Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete’s health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete’s health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.
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Supplementation with b-alanine plays an important role as a precursor of carnosine, the most effective intramuscular buffer, and has been seen as a potential ergogenic aid, especially for high-intensity modalities such as basketball. Thus, the aim of the present study was to investigate the effects of 6 weeks of b-alanine supplementation on repeated sprint ability (RSA) and technical performances in young elite Brazilian basketball players. In total, 27 young basketball players (17+1 years) were randomized into a b-alanine group (Gb – 6.4 g day À1 of b-alanine) and a placebo group (GP – 6.4 g day À1 of dextrose). Before and after the supplementation period the athletes performed a RSA test composed of ten 30 m sprints with two 180 changes of direction interspaced by 30 s of recovery. During the recovery period (i.e., after the sprints) the athletes performed a countermovement jump (CMJ) and a set of three free throws. After 48 h they performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1). Both groups increased the distance covered in the Yo-Yo IR1 after the supplementation period (p ¼ 0.001). On the other hand, both groups presented impairment in RSA time-performance (total time, best time, and mean time, p 0.04), while no significant changes were observed for technical task performances (i.e., CMJ and free throws) (p ! 0.07). No between-group interactions were observed for any variable measured (p ! 0.31). Thus, 6 weeks of b-alanine supplementation did not improve RSA or technical performances in young elite basketball players.
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Plyometric training and beta-alanine supplementation are common among soccer players, although its synergistic use had never been tested. Therefore, a randomized, double-blind, placebo-controlled trial was conducted to compare the effects of a plyometric training program, with or without beta-alanine supplementation, on maximal-intensity and endurance performance in female soccer players during an in-season training period. Athletes (23.7 ± 2.4 years) were assigned to either a plyometric training group receiving a placebo (PLACEBO, n = 8), a plyometric training group receiving beta-alanine supplementation (BA, n = 8), or a control group receiving placebo without following a plyometric training program (CONTROL, n = 9). Athletes were evaluated for single and repeated jumps and sprints, endurance, and change-of-direction speed performance before and after the intervention. Both plyometric training groups improved in explosive jumping (ES = 0.27 to 1.0), sprinting (ES = 0.31 to 0.78), repeated sprinting (ES = 0.39 to 0.91), 60 s repeated jumping (ES = 0.32 to 0.45), endurance (ES = 0.35 to 0.37), and change-of-direction speed performance (ES = 0.36 to 0.58), whereas no significant changes were observed for the CONTROL group. Nevertheless, compared to the CONTROL group, only the BA group showed greater improvements in endurance, repeated sprinting and repeated jumping performances. It was concluded that beta-alanine supplementation during plyometric training may add further adaptive changes related to endurance, repeated sprinting and jumping ability.
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Purpose: The present study investigated the effects of β-alanine supplementation only, and in combination with sprint-interval training (SIT), on training intensity, and energy provision and performance during exhaustive supramaximal-intensity cycling and a 4- and 10-km time trial (TT). Methods: Fourteen trained cyclists (VO2max = 4.5 ± 0.6 L·min) participated in this placebo-controlled, double-blind study. Subjects performed a supramaximal cycling test to exhaustion (equivalent to 120% VO2max) and a 4- and 10-km TT and 4 x 1-km sprints at three time points: before and after 28 d of supplementation loading (6.4 g·d) with β-alanine (n = 7) or a placebo (n = 7), and after a 5-wk supervised, SIT program performed twice weekly (repeated 1-km cycling sprints) whilst maintaining supplementation with β-alanine (1.2 g·d) or a placebo. Results: Following the loading period, sprint 3 and 4 of the 4 x 1-km sprint intervals were improved with β-alanine supplementation (4.5 ± 3.4% and 7.0 ± 4.0%; P < 0.05, respectively). After 5 wk of SIT, training intensity increased in both groups but the change was greater with β-alanine supplementation (9.9 ± 5.0% vs. 4.9 ± 5.0; P = 0.04). β-alanine supplementation also improved supramaximal cycling time to exhaustion to a greater extent than placebo (14.9 ± 9.2% vs. 9.0 ± 6.9%; P = 0.04), while 4- and 10-km TT performance improved to a similar magnitude in both groups. Following SIT, β-alanine also increased anaerobic capacity (5.5 ± 4.2%; P = 0.04), while VO2peak increased similarly in each group (3.1 ± 2.9% vs. 3.5 ± 2.9%; P < 0.05). Conclusion: These findings indicate that β-alanine supplementation enhances training intensity during SIT and provides additional benefits to exhaustive supramaximal cycling compared to SIT alone.
Objectives: This study compared the activity profile of different types of soccer-specific training activity with the demands of competitive international female match-play. Methods: Twenty-one female players from the Brazilian National Soccer Team were monitored in twenty-two on-field training sessions during the 30-day preparatory training camp prior to the 2016 Olympic Games and activities were categorized into warmup (WU), small sided games (SSG), technical and tactical training (TTT) and friendly matches (FM). The activity profile in each type of drill was then compared to the ones of the 6 matches performed during the Olympic Games. Results: Total distance and distance traveled at different speeds were higher during matches compared to WU, SSG and TTT, but not compared to FM. Frequency of accelerations was higher than matches during WU and TTT, and repeated acceleration and sprints were higher during SSG and TTT relative to match-play, whereas FM presented similar results. Conclusions: Although there were different acceleration and deceleration demands amongst WU, SSG, and TTT compared to match-play, FM was the only training activity which consistently replicated or exceeded Olympic matches’ physical demands.
The aim of this study was to determine the match locomotor characteristics of a sample of U-20 Brazilian female soccer players. Seven international matches were analyzed during the 2015 U-20 South American Championship, using global positioning technology. During a typical match, fullbacks and forwards covered greater distances in high-intensity running and sprinting than central defenders and midfielders (effect size [ES]=1.42-3.69). In the final 15 min of a game, total and high-intensity running distance and player load were ≈20 to 35% (ES=0.41-3.86) lower than in the first 15 min period for midfielders, fullbacks, forwards, and central defenders. Sprinting, and high-intensity running distances, and the frequency of accelerations >2 m.s⁻² immediately after the most intense 5-min period declined in forwards (ES=1.78-2.67), fullbacks (ES=1.96-5.25), midfielders (ES=1.66-3.77), and central defenders (ES=1.50-4.22). Maintaining 'high' levels of activity in the first half resulted in ≈19% reductions in the second half for sprinting distance and frequency of accelerations >2 m.s⁻² (ES=0.43 and 0.88), while increases in these locomotor activities were observed in situations with 'low' levels of activity (ES=0.64 and 1.12, for sprinting and accelerations >2 m.s⁻², respectively) (within-subject analysis). The data demonstrate that high-intensity efforts are reduced during various phases of international matches and overall activity patterns vary among playing positions. This information could be useful in the development and prescription of sex- and age-specific training regimes. © Georg Thieme Verlag KG Stuttgart · New York.
Objective To conduct a systematic review and meta-analysis of the evidence on the effects of β-alanine supplementation on exercise capacity and performance. Design This study was designed in accordance with PRISMA guidelines. A 3-level mixed effects model was employed to model effect sizes and account for dependencies within data. Data sources 3 databases (PubMed, Google Scholar, Web of Science) were searched using a number of terms (‘β-alanine’ and ‘Beta-alanine’ combined with ‘supplementation’, ‘exercise’, ‘training’, ‘athlete’, ‘performance’ and ‘carnosine’). Eligibility criteria for selecting studies Inclusion/exclusion criteria limited articles to double-blinded, placebo-controlled studies investigating the effects of β-alanine supplementation on an exercise measure. All healthy participant populations were considered, while supplementation protocols were restricted to chronic ingestion. Cross-over designs were excluded due to the long washout period for skeletal muscle carnosine following supplementation. A single outcome measure was extracted for each exercise protocol and converted to effect sizes for meta-analyses. Results 40 individual studies employing 65 different exercise protocols and totalling 70 exercise measures in 1461 participants were included in the analyses. A significant overall effect size of 0.18 (95% CI 0.08 to 0.28) was shown. Meta-regression demonstrated that exercise duration significantly (p=0.004) moderated effect sizes. Subgroup analyses also identified the type of exercise as a significant (p=0.013) moderator of effect sizes within an exercise time frame of 0.5–10 min with greater effect sizes for exercise capacity (0.4998 (95% CI 0.246 to 0.753)) versus performance (0.1078 (95% CI −0.201 to 0.416)). There was no moderating effect of training status (p=0.559), intermittent or continuous exercise (p=0.436) or total amount of β-alanine ingested (p=0.438). Co-supplementation with sodium bicarbonate resulted in the largest effect size when compared with placebo (0.43 (95% CI 0.22 to 0.64)). Summary/conclusions β-alanine had a significant overall effect while subgroup analyses revealed a number of modifying factors. These data allow individuals to make informed decisions as to the likelihood of an ergogenic effect with β-alanine supplementation based on their chosen exercise modality.