Effects of Creatine Supplementation on Lower-Limb Muscle Endurance Following an Acute Bout of Aerobic Exercise in Young Men

Abstract

We aimed to determine whether creatine supplementation influences lower-limb muscle endurance following an acute bout of aerobic exercise (AE) in young healthy men. Using a randomized, double-blind, placebo-controlled crossover design, 11 men (26.5 ± 6.2 years, body mass index 26.6 ± 2.1 kg/m2),with 12 months of experience in strength training (three times/week) and AE (two times/week) were randomized to receive creatine (20 g/day plus 20 g/day maltodextrin) and placebo (40 g/day maltodextrin) for 7 days, separated by a washout period of 14 days, before performing an acute bout of AE (30 min on treadmill at 80% baseline maximum velocity) which was followed by four sets of bilateral leg extension endurance exercise using a 10-repetition maximum protocol (10 RM)). There was a significant decrease in the number of repetitions performed in the third (Placebo: −20% vs. Creatine: −22%) and fourth set (Placebo: −22% vs. Creatine: −28%) compared with the first set (p < 0.05), with no differences between creatine and placebo. Additionally, no differences were observed between creatine and placebo for the total number of repetitions performed across all four sets (Placebo: 33.9 ± 7.0 vs. Creatine: 34.0 ± 6.9 repetitions, p = 0.97), nor for total work volume (Placebo: 3030.5 ± 1068.2 vs. Creatine: 3039.8 ± 1087.7 kg, p = 0.98). Short-term creatine supplementation has no effect on lower-limb muscle endurance following an acute bout of aerobic exercise in trained young men.

Full text

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Sports2020,8,12;doi:10.3390/sports8020012www.mdpi.com/journal/sports
Article
EffectsofCreatineSupplementationonLower‐Limb
MuscleEnduranceFollowinganAcuteBoutof
AerobicExerciseinYoungMen
ItamarP.Vieira
1
,AmandaG.dePaula
1
,PauloGentil
2
,ClaudePichard
3
,DarrenG.Candow
4

andGustavoD.Pimentel
1,
*
1
ClinicalandSportsNutritionResearchLaboratory(Labince),FacultyofNutrition,FederalUniversityof
Goias,74605‐080Goiânia,Brazil;itamarpef@gmail.com(I.P.V.);mnd.gms1@gmail.com(A.G.d.P.)
2
FacultyofPhysicalEducationandDance,FederalUniversityofGoias,74605‐080Goiânia,Brazil;
paulogentil@hotmail.com
3
ClinicalNutrition,GenevaUniversityHospital,1205Geneva,Switzerland;claude.pichard@unige.ch
4
FacultyofKinesiologyandHealthStudies,UniversityofRegina,Regina,SKS4SOA2,Canada;
darren.candow@uregina.ca
*Correspondence:gdpimentel@gmail.com;Tel.:+55‐62‐3209‐6270
Received:25November2019;Accepted:6January2020;Published:21January2020
Abstract:Weaimedtodeterminewhethercreatinesupplementationinfluenceslower‐limbmuscle
endurancefollowinganacuteboutofaerobicexercise(AE)inyounghealthymen.Usinga
randomized,double‐blind,placebo‐controlledcrossoverdesign,11men(26.5±6.2years,bodymass
index26.6±2.1kg/m
2
),with12monthsofexperienceinstrengthtraining(threetimes/week)andAE
(twotimes/week)wererandomizedtoreceivecreatine(20g/dayplus20g/daymaltodextrin)and
placebo(40g/daymaltodextrin)for7days,separatedbyawashoutperiodof14days,before
performinganacuteboutofAE(30minontreadmillat80%baselinemaximumvelocity)whichwas
followedbyfoursetsofbilaterallegextensionenduranceexerciseusinga10‐repetitionmaximum
protocol(10RM)).Therewasasignificantdecreaseinthenumberofrepetitionsperformedinthe
third(Placebo:−20%vs.Creatine:−22%)andfourthset(Placebo:−22%vs.Creatine:−28%)compared
withthefirstset(p<0.05),withnodifferencesbetweencreatineandplacebo.Additionally,no
differenceswereobservedbetweencreatineandplaceboforthetotalnumberofrepetitions
performedacrossallfoursets(Placebo:33.9±7.0vs.Creatine:34.0±6.9repetitions,p=0.97),nor
fortotalworkvolume(Placebo:3030.5±1068.2vs.Creatine:3039.8±1087.7kg,p=0.98).Short‐term
creatinesupplementationhasnoeffectonlower‐limbmuscleendurancefollowinganacuteboutof
aerobicexerciseintrainedyoungmen.
Keywords:creatine;aerobicexercise;concurrentexercise;strengthloss;muscle

1.Introduction
Concurrentexercise(CE)involvesthecombinationofaerobicexercise(AE)andresistance
traininginthesametrainingsession[1].CEiscommonpracticeamongexercisingindividualsand
athletesandincreasesphysicalperformanceandbodycomposition[2–6].However,previousstudies
haveshownthatperformingAEbeforeresistancetrainingresultsinacutedecreasesinmuscle
performance[2,4,7–10],possiblyduetoanincreaseinperipheralfatigue,AMP‐activatedprotein
kinase(AMPK)andPeroxisomeproliferator‐activatedreceptorgammacoactivator1‐alpha(PGC‐1α)
signalinganddecreaseinsatellitecellactivity[1].

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Supplementationwithcreatine,anorganicacidderivedfromreactionsinvolvingarginine,
methionine,andglycineinthekidneyandliver[1],hasbeenshowntoincreasemuscleperformance,
possiblybyinfluencinghigh‐energyphosphatemetabolism,satellitecellactivity,muscleprotein
kinetics,andinflammation[11,12].Theoretically,creatinesupplementationmaybeaneffective
nutritionalinterventionfollowingAEtomaintainmuscleperformance.Forexample,Painellietal.
[4]showedthatcreatinesupplementation(20g/dayfor7days+5g/daythereafter)maintainedlower‐
bodymuscleendurance(numberofrepetitionsperformed)followingacuteboutsofintermittentand
continuousAEinstrength‐trainedmalescomparedwithadecreaseinmaleswhoreceivedplacebo.
However,thisstudywaslimitedbytheparallelgroupdesign.
Thepurposeofthisstudywastodeterminewhethercreatinesupplementationmaintainsmuscle
performancefollowinganacuteboutofAEintrainedyoungmalesusingarandomized,cross‐over
design.Cross‐overdesignstypicallyreducetheinfluenceofconfoundingvariablesonthedependent
outcomemeasuresandareconsideredmorestatisticallypowerful(lessvariance)comparedwith
parallelgroupdesigns.BasedonthemechanisticactionsofcreatineandthefindingsofPainellietal.
[4],itwashypothesizedthatcreatinesupplementationwouldmaintainlower‐limbmuscleendurance
followinganacuteboutofAEcomparedwithplacebointrainedyoungmales.
2.Methods
2.1.Participants
Seventeenmenwith12monthsofstrengthtraining(threetimesperweek)andAE(twotimes
perweek)experiencevolunteered.Participantswereexcludediftheywerevegetarian,hadconsumed
proteinorcreatinesupplementssixmonthspriortothestartofthestudy,iftheyhadahistoryof
hormonaltherapyinterventionsoranabolicsteroiduse,oriftheyhadpre‐existingkidneyorliver
abnormalities.Participantswereinstructednottochangetheirdietorphysicalactivitypatterns
duringthestudy.Participantswereinformedoftherisksanddiscomfortsassociatedwiththestudy
beforeprovidingwrittenconsent.ExperimentaldesignwasapprovedbytheResearchEthics
Committee(no.2.507.216),andafterestablishingtheinclusionandexclusioncriteria,theparticipants
signedtheinformconsentform.
2.2.StudyOverview
Thestudywasadouble‐blind,placebo‐controlledcrossovertrialwhereparticipantswere
randomizedusingacomputer‐generatedschedule(https://www.randomizer.org/)toconsume
creatineandplacebofor7days,separatedbya14daywashoutperiod.Aftereach7days
supplementationphase,participantsperformedanacuteboutofAEexperimentaltestconsistingof
a30minrunonatreadmill(Technogym®,ExciteRun1000,Cesena,Italy)at80%maximumvelocity
(MV)obtainedinthetest.Immediatelyfollowingthetreadmillexercise,participantsperformedfour
setsofbilaterallegextensionexercise(Technogym®,LegExtensionMed,SãoPaulo,Brazil)withthe
loadobtainedonthe10‐repetitionmaximum(10RM)test.Allsetswereperformedtomomentary
musclefailureaspreviouslydefined[13].Restbetweensetswas2min.Bloodglucoseandlactate
concentrationsweredeterminedbeforeandaftertheacuteboutofAEtests.Duringthe14days
washoutperiod,nosupplementwasconsumed(Figure1).PriortotheacuteboutofAE,participants
wereinstructedtoabstainfromalcohol,caffeine,othersupplements,andstrenuousexercisefor48h.
Participantsarrivedfortesting1haftertheirlastmealandpre‐testfeedingwasstandardized(yogurt
withbanana).Adlibitumwaterconsumptionwasallowedduringthetestsandfoodintakewas
measuredusingthree24hfoodrecalls.Priortorandomizationandsupplementation,participants
performedafamiliarizationtrialwiththeexerciseequipmenttoreducetheamountoflearningwhich
mayhavecontributedtoourfindings.

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Figure1.Experimentaldesign.Afteranamnesis,anthropometricevaluation,strengthtests,and
exercisefamiliarization,elevenparticipantsonahigh‐proteindietandplaceboorcreatine
supplementationforoneweekweresubmittedtoacuteconcurrentexercisesession.Afterawashout
periodoffourteendays,thesameprotocolwasrepeated.
2.3.Supplementation
Participantsingested20gofcreatinemonohydrate(20g;MaxTitanium®,Supley,Matão,Brazil;
99.9%purity)and20gmaltodextrinor40gofmaltodextrin(placebo,MaxTitanium®,Supley,Matão,
Brazil)for7days.Afterthe14dayswashoutperiod,participantscrossed‐overandconsumedthe
oppositesupplementfor7days.Thetotaldailyamountofsupplementwasdividedintofourequal
portionsandconsumedwithfoodthroughouttheday.Creatineandplacebowereidenticalintaste,
color,texture,andappearance.Supplementpackageswereunmarkedsoneithertheparticipantnor
theresearcherknewthecontent.
2.4.AnthropometricMeasures
Bodymasswasmeasuredusingadigitalpersonalscale(HN‐289LA®OmronHealthcareCo.,
Muko,Kyoto,Japan)andheightusingaportablestadiometer(Sanny®,SãoPaulo,Brazil),andbody
massindex(BMI)wasthencalculated.Upper‐ andlower‐limbandwaistcircumferencewas
measuredtwiceusingatapemeasure.Skinfoldthicknesses(subcutaneousadiposetissue)were
measuredusingacaliper(Lange®SkinfolderCaliper,BetaTechnology,SantaCruz,USA)andbody
fatwascalculatedaccordingtotheJacksonandPollockprotocol[14].Anthropometricassessments
wereperformedbythesametrainedresearcher.
2.5.DietaryIntakeAnalyses
Dietaryintakewasassessedbyhavingparticipantsfilloutthree24hfooddiariesonseparate
days(twoweekdaysandoneweekendday)toevaluatehabitualfoodconsumption[15].Thedietary
intakeanalysisconsistedoftotalcalories,carbohydrate,lipids,proteins,leucine,valine,and
isoleucine.FoodintakecalculuswasperformedusingtheDietPro®software(version6.0,Viçosa,
Brazil)usingtheFoodDatabaseTableoftheUnitedStatesDepartmentofAgriculture[16].
2.6.MaximumGradedTest
Amaximalgradedexercisetestwasperformedonatreadmill(Technogym®,ExciteRun1000,
Cesena,Italy),withslopesetat1%.Afterawarm‐upthatconsistedofwalkingat6.0km/hfor3min,
thetreadmillwasadjustedwiththespeedof8.0km/h,followedbyanincreaseof1.0km/hineach
subsequentminuteuntiltheparticipantsreachedexhaustion.Thevelocityatthelastcompletestage
beforeexhaustionwasrecordastheMV.Participantswerestronglyencouragedverballytoexert
maximumeffort[17].


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2.7.Maximum‐RepetitionStrength(10RM)andStrengthEnduranceTest
The10‐repetitionmaximum(10RM)testwasperformedusingthelegextensionmachine
(Technogym®,LegExtensionMed,SãoPaulo,Brazil).Theproceduresfollowedtherecommendations
previouslydescribed[10,18].Theparticipantsperformedthewarm‐upwithtenrepetitions
performedataself‐selectedcomfortableload.Afterarestof5min,theestimated10RMloadwas
adjustedbasedonthetraininghistoryofeachparticipant.Ifthevolunteerwasnotabletoperform
tenrepetitionsorperformedmorethantenrepetitions,theloadwasadjustedforthenextattempt.
Onlythreeattemptswereallowed,withrestof5minbetweenthem.The10RMloadswereobtained
forallparticipantsintwotothreeattempts.Participantsperformedthetestswiththeirbacksin
contactwiththesupportandwerenotallowedtousetrunkmovementsorraisetheirhipsfromthe
chair.Thetestswerestoppedwhentheparticipantswereunabletodothemovementproperly(total
rangeofmotionwithoutchangesinthetechnique)fortwoconsecutiverepetitions.The
familiarizationofstrengthendurancetestinvolvedoftheconclusionoffoursetstofailureat80%of
theloadaspertheprotocolpublishedpreviously[4].Thetestswereperformedbytrained
professionalsandverbalmotivationwasusedinallsets.
2.8.BiochemicalAnalysis
Bloodlactatewasmeasuredusingaportablelactometer(Accutrend®Plus;RocheAccutrend
Plus,NewYork,NY,USA).Bloodglucosewasmeasuredbydigitalglucosemeter(Accu‐chek®
Active;Roche,SãoPaulo,Brazil).Allbloodsamplesweretakenfromthefingerbyatrained
professional.
2.9.StatisticalAnalyses
ThenormalityofthedatawastestedusingtheKolmogorov–Smirnovtest.General
characteristics,dietaryfoodintake,legextensionrepetitions,andbloodlactateconcentrationsare
presentedasmean±standarddeviationandglucoselevelsarepresentedasmedian(minimumand
maximum).Strengthdatawereanalyzedusingthetwo‐wayANOVAfollowedbyTukeytest.The
unpairedttestwasusedtocomparethetotalworkvolumeandbloodlactateconcentrationsbetween
groups.TheMann–Whitneytestwasusedtocomparethedeltabloodglucoseconcentrations.The
Fisherexacttestwasperformedtoassesstherateofparticipantswhocorrectlyguessedtheir
allocationinthegroup.AllstatisticalanalysesweredoneusingtheMedCalc®Seoul,Korea,software,
andp<0.05wasdefinedassignificantdifference.
3.Results
Ofthe17participantswhoinitiallyvolunteered,sixwereexcludedfornotadheringtotheproper
supplementationprotocol.Therefore,resultsfrom11participantswereusedintheanalyses.(Table
1).Priortostartingthestudy,allparticipantsfrombothgroupsingestedalow‐carb(3.0±1.0
g/kg/day)andhigh‐proteindiet(1.5±0.3g/kg/day),withnodifferenceindietaryintakebetween
interventionperiods(Table2).Nosideeffectswerereportedfromthesupplementationorexercise
intervention.Verbalconfirmationofsupplementationcompliancewas100%.
Table1.Participants’characteristics.
CharacteristicsMean±SD
Age(years)26.5±6.2
Bodyweight(kg)77.6±7.2
Height(m)1.7±0.0
Bodymassindex(kg/m2)26.6±2.1
Bodyfat(%)14.4±6.6
Workvolumelegextension(kg)88.1±18.6
Totalworkvolume(kg)3030.5±1068.2
Efforttimerunfor5km(min)25.5±2.6

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Table2.Dietaryfoodintake.
NutrientsMean±SD
Totalcalories(kcal)2196.6±702.9
Carbohydrate(%)43.6±8.2
Carbohydrate(g/kg)3.0±1.0
Protein(%)26.4±4.3
Protein(g/kg)1.5±0.3
BCAA(g)19.0±6.1
Leucine(g)8.3±2.9
Valine(g)5.8±1.8
Isoleucine(g)4.8±1.5
Lipids(%)29.9±9.5
BCAA:Branched‐chainaminoacids.
AfterAE,therewasasignificantreduction(p<0.05)inlegextensionmuscleendurance(number
ofrepetitionsperformed)inthethird(Placebo:−20%vs.Creatine:−22%)andfourthset(Placebo:
−22%vs.Creatine:−28%)comparedwiththefirstset.However,therewerenodifferencesbetween
creatineandplacebo(Figure2A).Acrossallfoursets,nodifferenceswereobservedinthetotal
numberofrepetitionsperformed(Placebo:33.9±7.0vs.Creatine:34.0±6.9repetitions,p=0.97)
(Figure2B).Additionally,nodifferenceintotalworkvolumewasfoundbetweencreatineand
placeboinkg(Placebo:3030.5±1068.2vs.Creatine:3039.8±1087.7kg,p=0.98)(Figure3)andjoules
(Placebo:3030.4±1068.2vs.Creatine:3035.5±1092.8J/m,p=0.99).

Figure2.Strengthenduranceinlegextension(repetitions)amongthesets(A)andlegextension(sum
ofrepetitions)(B).

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Figure3.Meanvaluefortotalwork(kg)usingthelegextensionmachineeitheronplaceboorcreatine
supplementation.
Therewerenosignificantdifferencesbetweencreatineandplaceboforchangesindeltablood
glucose(Placebo:5.0(−73.0–67.0)vs.Creatine:1.0(−53.0–49.0)mg/dL,p=0.73)andbloodlactate
(Placebo:5.1±2.9vs.Creatine:7.9±4.9nmol/L,p=0.11)concentrations(seeSupplementaryFigure
S1).
Regardingsupplementblindingefficacy,6/11participantscorrectlyguessedwhentheywere
consumingplaceboand5/11correctlyguessedwhentheywereconsumingcreatine,whichwasnot
statisticallydifferent(p=1.00).
4.Discussion
TherearetwohypothesesforthereductioninmuscleendurancefollowingAE,(i)acute;
peripheralfatiguetriggeredbymuscledamageandglycogendepletionduringAEtrainingreduces
theabilityofskeletalmuscletoproducetensionduringresistancetraining[2,3],and(ii)chronic;
skeletalmuscleattemptstoadapttobothformsoftraining,however,morpho‐functionaladaptations,
suchasfibertypeandsizeafterenduranceexerciseandweighttrainingarepartiallyopposed
resultinginaninterferenceeffect.
Thecurrentstudyaimedtoassesstheinfluenceofcreatinesupplementationonmuscle
endurancefollowinganacuteboutofAEintrainedyoungmales.Resultsshowedthatcreatinehad
noeffectonmuscleenduranceortotalworkperformedwhichisincontrasttothefindingsofPainelli
etal.[4],whoshowedthatcreatinesupplementation(20g/dayfor7days+5g/daythereafter)
maintainedlower‐bodymuscleendurance(numberofrepetitionsperformed)followingacutebouts
ofintermittentandcontinuousAEinstrength‐trainedmales(n=15)comparedwithadecreasein
males(n=16)whoreceivedplacebo.Theauthorssuggestthattheincreasedavailabilityofphosphoryl
creatineanditspotentialbufferingcapacity(reductionofH+ions)wouldberesponsiblefor
maintainingmuscleenduranceinthelegs.Furthermore,infemaleswhoperformedaleg‐press1RM
priortoandimmediatelyfollowinganacuteboutofenduranceexercise,therewasapositiveeffect
fromcreatinesupplementationontheperformanceoffoursetsoflegpressat80%of1RM[8].While
itisdifficulttocompareresultsacrossstudies,methodologicaldifferencesmaybeinvolved.Inthe
Painellietal.[4]study,legpressandchestpressmuscleendurance(bothmulti‐jointexercises)was
assessedwhereasweonlyassessedlegextensionendurance(single‐jointexercise).Furthermore,
femaleswereassessedinthestudybyAokiwhereasweassessedonlymales.Previousstudieshave
showndifferencesinmusclefatigability[6,8,19]andresponsivenesstocreatinesupplementation
betweensexes[20,21].
Additionally,nodifferenceinbloodlactateconcentrationswasreported.Thesedataaresimilar
tothosefromapreviousstudy[22].

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Ourdatashownopositiveeffectofcreatinesupplementationonmusclestrengthusinga
crossoverdesignandwithdietarycontrolduringthestudy.Consideringthattheparticipantswere
onahighprotein‐diet,thecreatinesupplementationmightbenotnecessary.Thismightbeexplained
becauseproteiningestioncanhelpinmusclerecovery[23]andmightinfluencerecoveryfromaerobic
activities.However,creatinesupplementationitseemsdidnotbringadditionalbenefitsinmenwho
intakeahigh‐proteinandlow‐carbdiet.
Arecentstudy[5]investigatedachronicproteinsupplementationeffect(6months)onmuscle
strengthinsedentarywomenandmenonCE.Menwhoingestedproteinsupplementation2.2
g/kg/day,showedhigherincreasesinstrengthinthebenchpresswhencomparedwiththegroupthat
ingested1.1g/kg/dayofprotein.Itisinterestingtonotethatmenwhoreceivedahigh‐protein(2.2
g/kg/day)groupingestedlowercarbohydrate(notlow‐carbdiet)thanthenormalprotein(1.1
g/kg/day)group.Ontheotherhand,inwell‐trainedmalecyclistswhoperformedanacuteexercise
session(high‐intensitycyclingand100drop‐jumps),20ghydrolysateproteinsupplementation
associatedwithahabitualhigh‐proteindiet(1.2g/kg/day)andmoderateincarbohydrate(6g/kg/day)
didnotalleviateexercise‐inducedmuscledamage[7].
Althoughtrainingenhancestheeffectivenessofsupplementationproteinduringresistance
exercise[24],theeffectsofhabitualconsumptionofahigh‐proteindietonmusclestrengthduring
concurrenttrainingarelimited[5].Itwouldbeinterestingiffuturestudiesevaluatetheeffectsof
creatinesupplementationunderhigh‐andlow‐habitualproteinandcarbohydrateintakes.
Althoughwedidnotmeasurethetimingofproteinintake,nosignificanteffectonmuscle
strengthisfoundduringtheresistancetraining[25].Thus,furtherstudiesarewarrantedtoexamine
theeffectsofahigh‐proteindietonmusclestrengthduringaCEbout.
4.1.StudyLimitations
Therewereseverallimitationstothisstudy.First,weuseda14dayswashoutperiodbetween
creatineandplaceboingestionwhichmaynothavebeenlongenoughtoabolishtheresidual(carry‐
over)effectsofcreatine.Forexample,Vandenbergheetal.[26]showedthatcreatinesupplementation
(20g/dayfor4days)increasedintramuscularPCrconcentrations,whichweremaintainedwitha
maintenancedosageofcreatine(5g/day)for10weeks.Uponcreatinecessation,intramuscularPCr
concentrationsremainedelevatedfor28days.Second,nomeasureofintramuscularcreatine(PCr,
freeCr)wasassessedpriortoeachtestingphase.Initialintramuscularcreatinelevelstypically
determinetheresponsivenesstocreatinesupplementation[27].Third,participantsmayhavealready
beenconsuminghighamountsofdietarycreatinefromprotein‐containingfoodproducts(i.e.,
seafood,meat,poultry)[28,29],whichattenuatedtheergogenicresponsetocreatine
supplementation.Foodrecordspriortothestartofsupplementationshowedthatparticipantswere
consumingapproximately1.5±0.3g/dayofprotein.Unfortunately,thefooddiariesdidnot
determinetheamountofdietarycreatineconsumed.Fourth,themajorityofintramuscularcreatine
isfoundintypeIImusclefibers.Youngindividualswiththehighestconcentrationandmusclecross‐
sectionalareaoftypeIIfibersrespondmorefavorablytocreatinesupplementation[30].
Unfortunately,nomeasureofmusclefibermorphologywasmadeinthisstudy.Finally,theabsence
ofpositiveeffectfoundcouldbeduetothefactofasmallsamplesize.Thus,astudywithalarge
samplesizeandparticipantswithdifferenttrainingstagesshouldbeexploredinthefuture.
5.Conclusions
Insummary,short‐termcreatinesupplementationhasnoeffectonlower‐limbmuscleendurance
followinganacuteboutofAEintrainedyoungmales.Ourresultsshownewinformationregarding
musclestrengthrecoveryafteranacuteboutofAEandraiseahypothesisthattheincreasein
carbohydrateintakecombinedwiththehigh‐proteindietshouldbeinvestigated.

Sports2020,8,128of9
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SupplementaryMaterials:Thefollowingareavailableonlineatwww.mdpi.com/xxx/s1,FigureS1:Deltablood
glucose(A)andlactate(B)concentrationsforparticipantseitheronplacebooroncreatinesupplementation.No
significantdifferencesobservedbetweengroups.
AuthorContributions:Conceptualization,I.P.V.,A.G.d.P.,P.G.,C.P.,D.G.C.andG.D.P.;DataCuration,I.P.V.,
A.G.d.P.,P.G.,G.D.P.;FormalAnalysis,I.P.V.,A.G.d.P.andG.D.P.;Investigation,I.P.V.,A.G.d.P.,P.G.and
G.D.P.;Supervision,P.G.,andG.D.P.;Writing—OriginalDraft,I.P.V.,A.G.d.P.,P.G.,C.P.andD.G.C.;Writing—
Review&Editing,P.G.,D.G.C.,andG.D.P.Allauthorshavereadandagreedtothepublishedversionofthe
manuscript.
Funding:Thisresearchreceivednoexternalfunding.
ConflictsofInterest:Nopotentialconflictofinteresttothisarticlehasbeenreported.
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
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