Article

Effects of re-warm-up protocols on the physical performance of soccer players: A systematic review with meta-analysis

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ABSTRACT: This systematic review aimed to (1) identify and summarize studies that have examined the effects of re-warm-up (RWU) protocols on the physical performance of soccer players (vertical height jump and sprinting time) and (2) establish a meta-comparison between performing a re-warm-up and not performing one regarding the outcomes of the aforementioned outcomes. A systematic review of EBSCO, PubMed, Scielo, SPORTDiscus, and Web of Science databases was performed on January 12th, 2021, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 892 studies initially identified, four studies were reviewed, and three of these were included in the present meta-analysis. Compared to a control condition, there was a moderate effect of RWU on vertical height jump (ES = 0.66; p = 0.001; I2 = 0.0%). However, compared to a control condition, there was a trivial effect of RWU on linear sprint time (ES = 0.19; p = 0.440; I2 = 38.4%). The nature of RWU enhances the performance of players with an emphasis on actions requiring vertical jumps. Therefore, the results provide essential and crucial information that soccer coaching staff can use to improve the performance of their teams. The reduced number of studies available for meta-analysis may have magnified the impact of heterogeneity on linear sprint time findings. More high-quality studies, with homogeneous study designs, may help to clarify the potential benefits of RWU on linear sprint time.
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Biology of Sport, Vol. 40 No2, 2023 335
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
INTRODUCTION
In soccer, re-warm-up (RWU) may increase players’ readiness to
perform actions at different intensity levels[1] at the start of the
second half of amatch, thereby enhancing their athletic perfor-
mance[2]. Indeed, RWU strategies have demonstrated that soccer
players’ acute explosive performance improved during the rst min-
utes of the second half of the match[3–5].
Areview of the literature reveals that the physical performance
of soccer players decreases during the second half of the match[6].
Common examples of this evidence can be found in studies show-
ing poorer performances for different variables, such as the
Effects of re-warm-up protocols on the physical performance
of soccer players: Asystematic review with meta-analysis
AUTHORS: Francisco Tomás González Fernández1,2, Hugo Sarmento3, Álvaro Infantes-Paniagua4,
Rodrigo Ramirez-Campillo5,6,7, Sixto González-Víllora4, Filipe Manuel Clemente8,9
1Department ofPhysicalActivity andSportSciences, PonticalUniversity ofComillas.CESAG, 07013Palma,
Spain
2SERResearchGroup,PonticalUniversityofComillas.CESAG,07013Palma,Spain
3University ofCoimbra,Research UnitforSport andPhysicalActivity.Facultyof SportSciencesand Physical
Education,Coimbra,Portugal
4FacultyofEducationofAlbacete,DepartmentofPhysicalEducation,ArtsEducation,andMusic,Universityof
Castilla-LaMancha.02071Albacete,Spain
5HumanPerformanceLaboratory.DepartmentofPhysicalActivitySciences.UniversidaddeLosLagos.Santiago,
Chile
6CentrodeInvestigaciónenFisiologíadelEjercicio.FacultaddeCiencias.UniversidadMayor.Santiago,Chile
7ExerciseandRehabilitationSciencesLaboratory.SchoolofPhysicalTherapy.FacultyofRehabilitationSciences.
UniversidadAndresBello.Santiago,Chile
8EscolaSuperiorDesportoeLazer,InstitutoPolitécnicodeVianadoCastelo,RuaEscolaIndustrialeComercial
deNun’Álvares,4900-347VianadoCastelo,Portugal
9InstitutodeTelecomunicações,DelegaçãodaCovilhã,Lisboa1049-001,Portugal
ABSTRACT:Thissystematicreviewaimedto(1)identifyandsummarizestudiesthathaveexaminedtheeffects
ofre-warm-up (RWU)protocols onthe physicalperformanceofsoccerplayers(verticaljumpheightandsprint
time)and(2)establishameta-comparisonbetweenperformingare-warm-upandnotperformingoneregarding
theoutcomes oftheaforementionedoutcomes.AsystematicreviewofEBSCO,PubMed,SciELO,SPORTDiscus,
andWebofSciencedatabaseswasperformedon12January,2021,accordingtothePreferredReportingItems
forSystematicReviews andMeta-Analyses(PRISMA) guidelines.Fromthe 892studiesinitiallyidentied, four
studieswere reviewed,and threeofthesewereincludedinthepresentmeta-analysis.Comparedtoacontrol
condition,therewas amoderateeffect ofRWUon verticaljumpheight (ES=0.66;
p
=0.001; I2=0.0%).
However, comparedto acontrol condition,there wasa trivialeffectofRWUonlinearsprinttime(ES=0.19;
p=0.440;I2=38.4%).ThenatureofRWUenhancestheperformanceofplayerswithanemphasisonactions
requiringverticaljumps.Therefore,theresultsprovideessentialinformationthatsoccercoachingstaffcanuse
toimprovetheperformanceoftheirteams.Thelimitednumberofstudiesavailableforthemeta-analysismay
havemagniedthe impactofheterogeneity onlinearsprint timendings.More high-qualitystudies,with
homogeneousstudydesigns,mayhelptoclarifythepotentialbenetsofRWUforlinearsprinttime.
CITATION: GonzálezFernándezFT,SarmentoH,Infantes-PaniaguaAetal.Effectsofre-warm-upprotocolson
thephysicalperformanceof soccerplayers:A systematicreviewwith meta-analysis.BiolSport.
2023;40(2):335–344.
Received:2021-08-13;Reviewed:2022-01-19;Re-submitted:2022-02-23;Accepted:2022-04-28;Published:2022-06-01.
number of high-intensity actions and the total distance covered in
the second half in comparison with the rst half[7,8]. Tradition-
ally, these effects have been linked to changes in muscle and core
temperatures[9] induced by passive half-time practice[10]. Nev-
ertheless, improvements in physical performance in the second
half have also been associated with RWU based on post-activa-
tion potentiation and supplementation with carbohydrate and caf-
feine[11]. Therefore, the direction of these physiological changes
depends on the active behaviours performed during the 15min-
utes of rest between halves[12].
Review Paper
DOI: https://doi.org/10.5114/biolsport.2023.116013
Key words:
Soccer
Football
Performance
Sports training
Warm-up
Neuromuscular
Vertical heigh jump
Linear sprinting
Half-time
Corresponding author:
Sixto González-Víllora
Faculty of Education of Albacete
Department of Physical
Education, Arts Education
and Music, University
of Castilla-La Mancha
02071 Albacete, Spain
E-mail: Sixto.Gonzalez@uclm.es
ORCID:
Francisco Tomás González
Fernández
0000-0002-1480-7521
Hugo Sarmento
0000-0001-8681-0642
Rodrigo Ramirez-Campillo
0000-0003-2035-3279
Álvaro Infantes-Paniagua
0000-0002-3552-300X
Sixto González-Víllora
0000-0003-2473-5223
Filipe Manuel Clemente
0000-0001-9813-2842
336
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
MATERIALS AND METHODS
Design and protocol
The systematic review strategy was conducted according to Preferred
Reporting Items for Systematic Reviews and Meta-analyses (PRISMA)
guidelines[16]. The protocol was registered with the International
Platform of Registered Systematic Review and Meta-Analysis Proto-
cols with the number 202110055 and DOI: 10.37766/inpla-
sy2021.1.0055.
Eligibility criteria
The inclusion and exclusion criteria can be found in Table1accord-
ing to the PICOS approach[17].
Information sources and search
Five electronic databases (EBSCO, PubMed, SciELO, SPORTDiscus,
and Web of Science) were explored for relevant publications prior to
29January 2022. The Web of Science database search was per-
formed restricting the search to the area of “sport sciences”. Keywords
and synonyms were entered in various combinations in the title,
abstract or keywords: (soccer OR football) AND (“re-warm-up” OR
“post-warm-up” OR “warm-up” OR “pre-activity” OR “post-activation
potentiation” OR “stretch*”) AND (“jump*” OR “sprint*” OR “change-
of-direction” OR “agility”).
The searches, the removal of duplicates, screening of titles and
abstracts, and analysis of the full texts in an independent way were
performed by two authors (FTGF and AIP). The inter-rater agreement
Player’s capability of keep high values of physical strength plays
an important role in the performance of soccer players in terms of
their maximal strength, jumping ability, and sprint performance[7,13]
and decrease over the course of amatch. In this sense, it is widely
known that efcient neuronal activation generates more applicated
weight reected in vertical jump height, and improves the change-
of-direction and linear sprinting performance in elite soccer play-
ers[14]. On the one hand, the higher level of fatigue generated dur-
ing the rst half and the team’s passive behaviour negatively impact
players’ sprint and jump performance at the beginning of the second
half. On the other hand, the implementation of RWU is positively re-
lated to an improvement in the performance at the beginning of the
second half[15].
Even though there is evidence supporting the inuence of acute
effects of RWU on the physical performance of soccer players, de-
scribed in asystematic review[4–6], little is known about its effect
on certain physical variables of the game, such as vertical jump
height, and sprint time. In fact, the most recent systematic review
in RWU (asfar as we know), centred the analysis in amyriad of per-
formance analyses without aquantitative synthesis in the form of
ameta-analysis[5]. Therefore, the aim of this systematic review was
twofold: (i) to identify and summarize studies that have examined
the effects of RWU protocols on the physical performance of soccer
players (vertical jump height and sprint time) and (ii) to establish
ameta-comparison between performing and not performing an RWU
protocol regarding vertical jump height and sprint time.
TABLE 1. Inclusion and exclusion criteria
Inclusion criteria Exclusion criteria
Population Soccer players of any age or sex with no injury or illness,
with normal vision, no partial/chronic injury or illness,
and no history of neuropsychological impairment.
Population other than soccer players or members of the
soccer player population with special conditions (e.g.,
injury, treatment, illness, diseases).
Intervention RWU protocols (always performed after an initial warm-
up) conducted under one of the two following possible
conditions:
(i) after the warm-up and before the match.
(ii) between the halves of the match.
Warm-up protocols.
Comparator Passive control conditions. Intervention conditions other than passive conditions.
Outcome Vertical jump height, and sprint time Physiological or physical conditions not related to the
included outcomes.
Study design Counterbalanced cross-over design (randomized and non-
randomized can be included since none of them reveal
signicant differences in control conditions).
Study designs that do not allow within-subjects comparisons
for the two conditions (control and RWU).
Additional criteria Only original and full-text studies written in English. Studies written in any language other than English. Articles
other than original research (e.g., reviews, letters to editors,
trial registrations, proposals for protocols, editorials, book
chapters, and conference abstracts).
Biology of Sport, Vol. 40 No2, 2023 337
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
was measured through Cohen’s kappa[17], which was found to be
good (kappa=0.70). Any discrepancy in the selection process was
solved by consensus with athird author (HS).
Data extraction
An ad-hoc Microsoft Excel sheet (Microsoft Corporation, Redmond,
WA, USA) was used to assess inclusion requirements in accordance
with the Cochrane Consumers and Communication Review Group’s
data extraction template[18]. The Excel sheet was used to assess
inclusion requirements and subsequently tested for all selected stud-
ies. The process was independently conducted by two authors (HSand
FTGF). Any disagreement regarding study eligibility was resolved in
adiscussion. Full text articles excluded, with reasons, were recorded.
All the records were stored in the sheet.
Data items
The outcomes chosen for this systematic review and meta-analysis
included vertical jump height (VJH) and sprint time (ST). The VJH
(measured in cm) was usually assessed during acountermovement
jump (CMJ) with or without arm swing. The linear ST (measured
in seconds) at different distances was also collected, without in-
cluding values of partial times. Additionally, the following data
items were extracted: (i) type of study design, number of participants
(n), age group (youth, adults or both), sex (men, women or both),
competitive level, moment of the season; (ii) characteristics of the
RWU protocol (duration and intensity); (iii) moment of the match
(after warm-up and between halves); (iv) characteristics of the
experimental approach to the problem, procedures and settings of
each study.
Methodological assessment
The included studies were assessed according to their methodologi-
cal quality with the Risk of Bias 2(RoB2) tool for RCTs[19]. We
conducted arisk of bias assessment using the RoB-2 tool for RCTs[20]
and the ROBINS-I for nonrandomized interventions[21]. These tools
allow one to assess the risk of bias (i.e., “low risk,” “some concerns,”
or “high risk”) of several dimensions, which vary according to the
study design (namely, bias arising from the randomization process,
bias due to deviations from intended interventions, bias due to miss-
ing outcome data, bias in measurement of the outcome, and bias in
selection of the reported result). Altogether an overall level of risk of
bias per study was computed. Risk of bias assessments were based
on the published articles. Two of the authors (FTGF and AIP) inde-
pendently screened and assessed the included articles. The inter-
rater agreement was very good (Cohen’s kappa=0.99). Discrepan-
cies were solved by consensus between the two authors.
Summary measures, synthesis of results, and publication bias
Although meta-analyses can be done with as few as two studies[22],
considering the fact that reduced sample sizes are common in the
sports science literature[23], meta-analysis was only conducted in
the present case when three or more studies were available for the
same outcome. Effect sizes (ES; Hedge’s g) for each outcome (i.e.,
linear sprint; vertical jump) in the experimental and control groups
were calculated using pre-intervention and post-intervention mean
and standard deviation (SD) for each outcome. Data were standard-
ized using post-intervention SD values. The random-effects model
was used to account for differences between studies that might im-
pact the intervention effect[24–25]. The ES values are presented
with 95% condence intervals (95% CIs). Calculated ES were inter-
preted using the following scale: < 0.2, trivial; 0.2–0.6,
small;>0.6–1.2, moderate;>1.2–2.0, large;>2.0_4.0, very
large;>4.0, extremely large[26]. In studies including more than
one intervention group, the sample size in the active control group
was proportionately divided to facilitate comparisons across multiple
groups[27] The impact of heterogeneity in the ndings was assessed
using the I2 statistic, with values of<25%, 25–75%, and>75%
representing low, moderate, and high levels of heterogeneity, respec-
tively. The risk of reporting bias was explored using Egger’s test[28],
with p <0.05implying bias. To adjust for risk of reporting bias,
asensitivity analysis was conducted using the trim and ll meth-
od[29], with L0 as the default estimator for the number of missing
studies[30]. All analyses were carried out using the Comprehensive
Meta-Analysis software (Version 2.0; Biostat, Englewood, NJ, USA).
Statistical signicance was set at p<0.05.
RESULTS
Study identification and selection
The search of databases identied atotal of 1309titles (PubMed
=267; Scopus=352; SPORTDiscus=327; Web of Science
=363). These studies were then exported to reference manager
software (EndNote X9, Clarivate Analytics, Philadelphia, PA, USA).
Duplicates (664references) were subsequently removed either
automatically or manually. The remaining 645articles were
screened for their relevance based on the information contained in
titles and abstracts and considering the selection and exclusion
criteria (seeTable1). This resulted in the removal of afurther
619studies. Following the screening procedure, 26articles were
selected for in depth reading and analysis. After reading full texts,
four studies were selected (Figure1).
Methodological quality
Table2shows the overall methodological quality assessment of the
cross-sectional studies. Two out of three studies were classied as
presenting high risk of bias studies, based on their overall RoB 2qual-
ity scale[9,31], and the other one was considered as having some
concerns[32], while another study was classied as showing serious
risk of bias in ROBINS-I[15]. Some issues were found regarding the
quality of the information reported on the randomization process, the
reporting of possible deviations from the intended interventions, the
treatment of missing outcome data, and the selection of the re-
ported result.
338
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
FIG. 1. PRISMA ow diagram highlighting the selection process for studies.
TABLE 2. Methodological assessment of the included studies.
Study Outcome D1a D1b D2 D3 D4 D5 DS Overall
Edholm etal.[15]* All S L M L NI M M S
Fashioni, Langley & Page[31] All SC SC H L SC L H
Lovell etal.[32] All SC SC L L SC LSC
Mohr etal.[9] All SC SC H L SC H
Note. D1a: Randomization process; D1b: Timing of identication or recruitment of participants in acluster-randomized trial; D2:
Deviations from the intended interventions; D3: Missing outcome data; D4: Measurement of the outcome; D5: Selection of the reported
result; DS: Period and carryover effects. C: Critical; H: High risk; L: Low risk; M: Moderate; NI: No information; S: Serious; SC: Some
concerns. * Assessment from ROBINS-I: D1a: Bias due to confounding; D1b: Bias in selection of participants for the study; D2: Bias
in classication of interventions; D3: Bias due to deviations from intended interventions; D4: Bias due to missing data; D5: Bias in
measurement of outcomes; DS: Bias in selection of the reported result.
Biology of Sport, Vol. 40 No2, 2023 339
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
Characteristics of individual studies
The characteristics of the included studies and details of the RWU
protocols can be found in Table3.
Three out of the four studies followed a cross-over de-
sign[15,31,32], and the other one was arandomized parallel-
groups study[9]. Regarding the participants, all studies were per-
formed with male soccer players[9,15,31,32]. The level of
participants was amateur in two studies[9,32], whereas one study
included semi-professional players[15], and the other one involved
professional players[31]. In addition, sample sizes varied from
10participants[15,32] to 22participants[31]. The parallel-group
study included 16participants (eight in each group)[9]. Lastly, con-
cerning the studies’ RWU protocols, all studies employed atradition-
al RWU during the 15-min resting period between match halves
while approaching the active RWU (7ʹ rest + 7ʹ jog + exercises at
135beats/min[9], 9ʹ rest + 5ʹ intermittent agility exercises[15],
7 rest + 7ʹ jog and calisthenics[31] and 12ʹ + 3ʹ RWU[32]).
Sprint time was measured in all studies[9,15,31,32], through
repeated sprint test, 30m[9], 10msprint[15,32], and 5m,
10mand 20msprint[31]. Non-signicant effects of RWU were
found on 30msprint[9]. In fact, positive effects of RWU were found
on 10msprint[15,32]. Last, 20msprint improved after RWU,
but non-signicant effects were found on 5mand 10m[31].
Vertical jump height was assessed with CMJ[15,31,32] and
squat jump (SJ)[31]. Signicant positive effects of RWU protocols
were found on CMJ[15,31,32] and SJ[31].
Effects of re-warm-up on vertical jump height
Three studies provided data for vertical jump height (pooled n=104).
Compared to acontrol condition, there was amoderate effect of RWU
TABLE 3. Characteristics of selected studies
Study Age (years)
Mean ± SD
Sample
size (
n
)Level / Sex RWU
characteristics Design Outcomes
Vertical jump height Sprint time
Mohr etal.[9]
27.0. ± 1.5 8 CG
8 EG
Male Soccer
players
competing in
the Danish 4th
Division
Re Warm Up1:
15 rest (control)
Re Warm Up2: 7
rest + 7 jog +
exercises at
135beat/ min
Randomized
(participants)
Parallel groups
Re Warm Up2>Re
Warm Up
1d=−0.66
0.67%
Test (Repeated sprint
test. 30m sprint)
Lovell etal.[32]
20 ± 1 10
Semi-
professional
male soccer
players
Re Warm Up1:
rest (control)
Re Warm Up2: 9
rest + 5
Intermittent Agility
Exercise
Re Warm Up3: 9
rest+5 Whole
Body vibration at
40Hz
Counterbalanced
Crossover design.
Re Warm Up2>Re
Warm Up 1
Test (CMJ)
Re Warm Up2>Re
Warm Up1
Test (10msprint)
Edholm
etal. [15]
Range
18–33 22
Twenty-two
male
professional
soccer
players
Re Warm Up1:
traditional
half-time break
Re Warm Up2: 7
rest + 7: jog and
calisthenics
Crossover design.
Re Warm Up2>Re
Warm Up1
d=0.293.02%
Test (CMJ)
Re Warm Up2>Re
Warm Up1
d=−0.72− 2.02%
Test (10msprint)
Fashioni, Langley &
Page[31]
23 ± 4 10Male Amateur
Soccer Players
Control Trial:
15-min Half Time
Passive
Re Warm Up
Trial: 12min +
3min Re Warm
Up.
Cross-over design.
Re Warm Up
improvement in squat
(d=0.6; CON:
26.96 ± 5.00CM; RWU:
30.17 ± 5.13)
II) CMJ=(d=07;
CON: 28.15 ± 4.72CM;
RWU: 31.53 ± 5.43)
Test (CMJand AJ)
Re Warm Up
improvement in
20msprint times.
(d=0.6; CON:
3.42 ± 0.20S; RWU:
3.32 ± 0.12).
Test (5m, 10m and
20m sprint)
340
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
Effects of RWU on vertical jump height
Traditionally, the countermovement jump (CMJ) has been explored
in different ways (SeeMorin etal., 2019 for more information[33]),
namely as aphysical quality associated with lower-limb power[34]
and as areadiness marker to detect the inuence of fatigue on neu-
romuscular properties[35]. In the case of soccer, CMJ has also been
conrmed as adeterminant of other qualities such as sprinting or
change of direction[36,37]. Since CMJ is dependent on the recruit-
ment of higher-order motor units, potentiation mechanisms, and/or
muscle activation[38,39], it can be expected that warming up plays
an important role in immediate performance maximization.
The meta-analysis presented in this systematic review revealed
moderate and signicant benecial effects of RWU protocols on CMJ.
These changes were identied using the p-value and effect size. How-
ever, in apractical scenario, it would be necessary to analyse the
raw data for the smallest worthwhile change. However, in this par-
ticular review, we did not have access to the raw data of included
articles, which justies the option for using the p-value and effect
size to sustain the evidence of the benecial effects of RWU on CMJ.
Although the protocols of exposure to RWU were generally based on
RAMP (raise, activate, mobilize, and potentiate), the effects were
on vertical jump height with no heterogeneity (ES=0.66; 95%
CI=0.28to 1.05; p=0.001; I2=0.0%; Egger’s test p=0.098;
Figure2). The weight used in each study in the analysis ranged from
18.8% to 42.5%.
Effects of re-warm-up on sprint time
Three studies provided data for linear sprint time (pooled n=104).
Compared to acontrol condition, there was atrivial effect of RWU
on linear sprint time with moderate heterogeneity (ES=0.19; 95%
CI=-0.30to 0.69; p=0.440; I2=38.4%; Egger’s test p=0.692;
Figure3). The relative weight of each study in the analysis ranged
from 21.8% to 34.0%.
DISCUSSION
The aim of this systematic review with meta-analysis was to determine
the effects of RWU protocols on the vertical jump height and sprint-
ing performance of soccer players. The meta-analysis revealed asig-
nicant and moderate benecial effect of RWU on players’ vertical
jump height, although no signicant benets were found in sprinting
performance.
FIG. 2. Forest plot of effects of re-warm-up on vertical jump height compared to acontrol condition.
FIG. 3. Forest plot of effects of re-warm-up on sprint time compared to acontrol condition.
Biology of Sport, Vol. 40 No2, 2023 341
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
large enough to signify the importance of using RWU to preserve
players’ jumping performance immediately before the match re-start.
Although post-activation potentiation using heavy loads appears to
represent abetter neuromuscular stimulus for enhancing vertical
jump[40], the protocols consisting of running, dynamic stretching,
and straight sprinting[15,31]; intermittent agility exercises[32]; or
whole-body vibrations[32] had afavourable effect on the reduction
the decremental effects of rest on vertical jump performance.
It is reasonable to hypothesize that elevated muscle temperatures
improve the recruitment of motor units, possibly justifying the ben-
ecial effects of RWU[15]. Additionally, considering that meaning-
ful decreases in eccentric hamstring strength can be observed after
inactivity during half-time[32], are-activation before the second half
of amatch is also recommended to enhance vertical jump height,
which requires the potentiation of muscles to increase players’
performance.
Effects of RWU on sprint time
Sprinting is one of the most important high-intensity demands in
soccer. Although it rarely occurs during matches[41], this action is
crucial since it is related to decisive moments of matches that precede
goal-scoring opportunities[42]. Usually, sprints last 2–4sover dis-
tances shorter than 20m[43]. Since sprinting performance depends
on neuromuscular readiness and neural activation[44], the proper
physiological conditions (e.g., induced by warming up) should be
ensured[45]. Warming up is expected to immediately benet sprint-
ing performance, considering that it plays an important role in fully
activating the working musculature and recruiting motoneurons to
support the high magnitude of contractions[9,46]. Considering that
the half-time break presents along period of rest/inactivity, it can
induce adrop in muscle temperature (~1.5°C), thus negatively im-
pacting sprinting performance[9].
The meta-analysis conducted in the current systematic review re-
vealed atrivial and non-signicant benecial effect of RWU on sprint-
ing performance. Among the included studies, Lovell etal.[32] and
Edholm etal.[15] reported abenecial and signicant effect of RWU
strategies in comparison to control conditions. Lovell etal.[32] stat-
ed that temperature was higher in the RWU group, possibly contrib-
uting to the players’ muscle readiness for sprinting. However, neuro-
muscular facilitation caused by reex potentiation could be another
physiological cause of this benet of RWU[46]. In adifferent study,
the effects of RWU on sprinting performance were positive immedi-
ately after exposure, as well as ten and 15minutes after exposure.
Again, additional factors related to fatigue during the match could
have impacted the comparisons[43]. Therefore, the literature pro-
vides relevant information about the requirements for high level soc-
cer players and specic details to ensure the stability and solidity of
second-half performance.
Generally, the individual studies emphasize the benets of RWU
for mitigating the decline in sprinting performance induced by the
half-time rest period. Thus, from apractical point of view, coaches
can choose to use acombined approach such as jogging, skipping,
dynamic stretching, and straight sprinting[15,31], or implement
intermittent agility exercises[32], or use whole-body vibrations[32],
or even selected alternative strategies such as potentiation-post ac-
tivation based on lifting moderate-to-high loads[47] or short high
cycling efforts[48].
Study limitations, future research, and practical implications
This systematic review has some limitations. One is the small
number of included articles, which should be considered alimiting
factor regarding the generalization of evidence. For example, the
impact of heterogeneity (i.e., I2=0.0%) on the vertical jump height
results was low. In contrast, agreater impact of heterogeneity (i.e.,
I2=38.4%) affected the linear sprint time ndings. The limited
number of studies available for meta-analysis may have magnied
the impact of heterogeneity on linear sprint time ndings. More
high-quality studies, with homogeneous study designs, may help
to clarify the potential benets of RWU for linear sprint time. An-
other limitation is that only articles written in English were in-
cluded; thus, some relevant literature may have been excluded.
However, the results found are promising regarding the implemen-
tation of RWU strategies in soccer players. Eventually, short,
moderate-to-high demanding activities should be ensured to max-
imize the increase in muscle temperature and neuromuscular ac-
tivation in the shortest time possible, thus saving some time for
the recovery during half-time[5].
Future research should consider determining the most adequate
and practicable RWU strategies for soccer players, namely by com-
paring post-activation performance enhancement strategies, RAMP,
whole-body vibration, or cycling. Duration of exposure and an anal-
ysis of this parameter’s impact on the rst minutes of the match
should also be integrated into future reports. Determining the inten-
sity and identifying thresholds should also be considered, namely for
individualizing these strategies. As aconsequence, more research is
needed on the effects of RWU, as the dose-response effects on indi-
vidual soccer players need to be better understood in order to achieve
the best possible performance.
As example, the time of RWU is critical. As suggested in astudy
conducted in twelve amateur players comparing the effects of a10-
and 20-minute regular warm-up[49], adetrimental effect of the lon-
ger period on the muscular power output was found, followed by ex-
cessive thermal discomfort and fatigue. Similar evidence was found
in astudy comparing 8-, 15- and 25-minute warm-up protocols, in
which only the condition of 8minutes ensured signicant improve-
ments in the acceleration ability of soccer players[50]. Thus, con-
sidering these examples, time-efcient and optimal RWU strategies
should be compared in crossover study designs. However, the sav-
ing of time should not compromise the effectiveness of RWU for im-
proving some protective factors such as stabilization, balance, or ex-
tremity symmetries. As an example, astudy using the regular warm-up
of FIFA11+ revealed the potential of this condition for improving
342
Francisco Tomás González Fernández et al. Effects of re-warm-up protocols on soccer players
unilateral jumping and dynamic balance and reducing lower limb ex-
tremity symmetries in female soccer players[51].
For now, it is possible to argue only that RWU strategies do not
cause negative effects in comparison to control conditions and that
they have afavourable effect on vertical jump height. For soccer
coaching staff, more evidence is needed on the cost-benet ratio of
implementing an RWU in their match routines, eventually consider-
ing the extent of benets to the rst high-intensity demands occur-
ring in the re-start of matches.
Apractical application of this review is the improvement of sub-
stitution decision-making in high-performance matches[52,53]. In
fact, if soccer coaching staff have information about the evidence of
RWU, they will be able to make much more effective player chang-
es according to the specic tactics with which they intend to change
the dynamics of amatch (e.g., which player to send out when their
team is trailing by one goal and there are 25minutes left in the
match). In this case, it would be appropriate to put players with high
jumping power on the pitch, as this could be benecial for nishing
or heading shots.
In turn, this review provides key information when it comes to
signing players and building abalanced squad, as the factors that
have been shown to be positive can be taken into account to select
the best players for atop-level team.
CONCLUSIONS
The most relevant contribution of this work is that there is asigni-
cant and moderate benecial effect of RWU on vertical jump height,
but not on sprinting performance, in soccer players. This information
is crucial for soccer coaching staff to improve the performance of
their teams. Given the small number of publications found, this re-
search line can be described as emerging, as more studies are need-
ed to consolidate the scientic evidence found.
Funding
Filipe Manuel Clemente: This work is funded by Fundação para
aCiência eTecnologia/ Ministério da Ciência, Tecnologia eEnsino
Superior through national funds and when applicable co-funded EU
funds under the project UIDB/50008/2020. Also was supported by
the startup Football Connection (FOOC) (Marca Nº 4.073.379). No
other specic sources of funding were used to assist in the prepara-
tion of this article.
Conicts of interest/Competing interests
The authors declare that they have no conicts of interest relevant
to the content of this review.
Acknowledgments
FTGF gratefully acknowledges that is supported by Beca de Movilidad
Erasmus+ para recibir formación (PDI) Erasmus 2020–2021. AIP
(FPU16/00082) gratefully acknowledges that his collaboration in
this work was supported by the Spanish Ministry of Universities (grant
number: EST19/00498).
Authorship Contributions
FTGF, HS, AIP and FMC lead the project, established the protocol
and wrote and revised the original manuscript. RRC and SGV wrote
and revised the original manuscript.
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