Type and quantity of physical activity and screen based activities of students from the 7th to the 12th grades: characterization and association

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w w w . e l s e v i e r . p t / r p s p

Original

article

Type

and

quantity

of

physical

activity

and

screen

based

activities

of

students

from

the

7th

to

the

12th

grades:

Characterization

and

association

Anabela

G. Silva

a,b,∗

,

Alexandra

Queirós

a,c

,

Maritza

Neto

d

,

Nelson

P. Rocha

c,e

a_School_of_Health_Sciences,_University_of_Aveiro,_Aveiro,_Portugal

b_Center_for_Health_Technology_and_Services_Research_{(CINTESIS.UA),}_Aveiro,_Portugal

c_Institute_of_Electronics_and_Telematics_Engineering_of_Aveiro_(IEETA),_University_of_Aveiro,_Aveiro,_Portugal d_Primary_Healthcare_Center,_Ílhavo,_Portugal

e_Department_of_Medical_Sciences,_University_of_Aveiro,_Aveiro,_Portugal

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received14February2016 Accepted19July2016

Availableonline20October2016 Keywords:

Physicalactivity Students Screentime

a

b

s

t

r

a

c

t

Aim:Toexaminetheassociationbetweenself-reportedphysicalactivityandself-reported screenbasedtime.

Materialsandmethods:969highschoolstudentsfilledinaquestionnaireonphysicalactivity andscreenbasedactivities.Correlationanalysisbetweentimespentinmoderate/vigorous physicalactivitiesandtimespentinscreenbasedactivitieswereperformed.

Results:NoassociationwasfoundbetweenphysicalactivityandtimespentwatchingTV, playingorusingcomputers.Alowcorrelationwasfoundbetweentimeusingmobilephones andtimespentperformingmoderatephysicalactivities(r=0.09,p<0.05),andvigorous phys-icalactivities(r=0.13,p<0.05).

Sa ´udeP ´ublica.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Tipo

e

quantidade

de

atividade

física

e

uso

de

dispositivos

eletrónicos

de

estudantes

do

7.

◦

_ao

_12.

◦

_ano:

_{caracterizac¸ão}

_e

_{associac¸ão}

Palavras-chave: Atividadefísica Estudantes

Dispositivoseletrónicos

r

e

s

u

m

o

Objetivos:Explorara associac¸ãoentreoníveldeatividadefísicaeousode dispositivos eletrónicos.

Materiaisemétodos:Novecentosesessentaenovealunosdosecundáriopreencheramum questionáriosobre atividadefísicae usodedispositivos eletrónicos.Foirealizada uma análisedecorrelac¸ãoentreotempodespendidoematividadefísicamoderadaeintensa eousodedispositivoseletrónicos.

∗ _{Corresponding}_author.

E-mailaddress:[email protected](A.G.Silva). http://dx.doi.org/10.1016/j.rpsp.2016.07.001

0870-9025/©2016TheAuthors.PublishedbyElsevierEspa ña,S.L.U.onbehalfofEscolaNacionaldeSa údeP ública.Thisisanopenaccess articleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

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Resultados: Nãohácorrelac¸ãoentreaatividadefísicaevertelevisão,jogarouusar com-putadores.Háumacorrelac¸ãobaixaentreousodetelemóveiseaatividadefísicamoderada (r=0,09,p<0,05)evigorosa(r=0,13,p<0,05).

Conclusões: Estesresultadossugeremqueousodedispositivoseletrónicosnãointerfere comapráticadaatividadefísica.

Introduction

Theevidenceofthebenefitsofphysicalactivityin maintain-inggoodhealthandfunctionisunquestionable.Forchildren and adolescents in particular, physical activity has been showntobe associatedwithpositivechanges inadiposity, skeletalhealth,psychologicalhealth,improvedself-esteem, fewerdepressivesymptoms1_and_improved_{cardiorespiratory} fitness.2_Furthermore,_it_appears_to_have_long_term_influence onpreventing weightgain,obesity, coronaryheart disease, type2diabetesmellitus,Alzheimer’sdiseaseanddementia.3 Despitetheconsensualbenefitsofphysicalactivityacrossthe lifespan, studies haveshown a declinein physicalactivity andanincreaseinsedentarybehaviorsduringadolescence.3,4 Increased sedentary behaviors in adolescence have been associated with time spent using electronic devices such asmobile phones,computers, television (i.e.,screen time), which in turn, has been shown to be related with hyper-activity/inattentionproblems,lesspsychologicalwell-being, less perceived quality of life,5 _obesity6 _and _increased_pain prevalence.7

Thehypothesisthat screentimecould displacephysical activity hasbeen proposed.8 _However, _the_evidence _on_the association between increased screen time and decreased physical activity is conflicting. A few studies have found aninverseassociationbetweenphysicalactivityandscreen time,9–11 _while _others _have _found _no _association _between these factors.12,13 _A _recent _systematic _review _identified a negative association between screen time and physical activity/fitness,11_while_a_longitudinal_study_found_an_inverse but non-substantive association between TV/DVD use and leisure physical activity and no association between com-puter/gameuseandleisurephysicalactivity,14_suggesting_that the associationmight dependon the typeofscreen based activity.Furthermore,acrosscountrystudy9_suggests_that_the strengthofthe associationbetweenscreen basedactivities andphysicalactivitydependsongender,country/region,type ofscreen-basedactivityandintensityofphysicalactivity.For example,watchingtelevision,gamingandusingacomputer showeddifferentpatternsofassociationwithphysicalactivity andthestrengthofassociationdependedonwhether vigor-ousphysicalactivityormoderatetovigorousphysicalactivity was considered in the analysis. In addition, the strength and directionof the association variedbetween the South European countries and the Nordic European countries.9 Therefore,moreresearchisneededinPortugalinvestigating thepotentialassociationbetweenscreen timeandphysical activity forstudents, in particular whether an association

betweenthesevariablesmightdependontheintensityand type of physical activity or type of screen based activity. The main aim of this study is to investigate whether an associationexistsbetweenself-reportedphysicalactivityand self-reportedscreenbasedtimewhenconsideringthe inten-sity (moderate or vigorous)and type (e.g. football, skating, cycling)ofthephysicalactivityandthetypeofscreenbased activity(watchingTV/DVD,playing,usingmobilephonesand computers)inasampleofPortuguesestudentsfromthe7th tothe 12thgrades. Secondaryaimsare tocharacterize the typeofphysicalactivitiesandscreenbasedactivitiesinwhich students areinvolvedand timeperweekspentperforming them.

Methods

This study received Ethical approval from the Council of Ethics and Deontology, University of Aveiro. Written con-sent was obtained from the students or from both the students and their parents if students were younger than 16yearsold.

Studydesignandpopulation

ThisstudytookplaceintheCouncilofÍlhavo.ThisCouncil spentapproximately1.002.6eurosintheyearof2012ingames and sports,aninvestmentthatishigherthan theNational average (dataretrieved from http://www.pordata.pt/on the 30th ofMay 2016) andits offer interms ofsports/physical activityincludes:swimming,athletics,handball,basket, foot-ball, martialarts, ballet,tennis, sailing, surf andcanoeing. This Council has5 schools withthe 7th or higher grades. These5schoolshadapproximately 1330studentsfrom the 7thtothe12thgradeatthetimeofdatacollection.Allthese students were invited to participate in the study. A ques-tionnairewasadministeredusinganElectronicDataCapture (uEDCTM₎_Solution_developed_for_this_study._This_uEDCTM

solu-tion (uedc.iuz.pt)isanElectronic DataCapturesolutionfor thehealthcarefield,usinganinformationsystemtocollect andprocessclinicaldata,involvingpatients,researchersand healthcare professionals. It enables the setup of a clinical study,inaccordancewithanestablishedprotocoldefinedby thestudypromotor.Duringaphysicaleducationlessoneach studentwasgivenanindividualpasswordandloginandasked tocompletetheonlinequestionnaire.Studentsnotatschool onthedayofdatacollectionwereinvitedtoparticipateon another day. Data were collected betweenMarch and June 2014.

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Measures

Demographicdata

Studentswereaskedtoenterdataonsex,ageandschoolyear.

Physicalactivity

Studentswereaskedwhether:(1)theyparticipatedregularly inthephysicaleducationclasses;(2)theyparticipatedin mod-erate physicalactivities other than the physical education classes;andwhether(3)theyparticipatedinvigorous physi-calactivitiesotherthanthephysicaleducationclasses.Those reportingtoparticipateinmoderateorvigorousphysical activ-ityhadtoanswerthreeadditionalquestionsrelatedto:type ofactivity,number ofdaysperweek(1–7)and mean dura-tion ofeach activity per session (minimum10min).These questions were adaptedfrom Lang.15 _Response_options _for the moderate physicalactivities question were: walking to school,walkingingeneral(otherthantoschool),cycling, skat-ing,rollerskating,others.Responseoptionsforthevigorous physicalactivitiesquestionwere:handball,running,martial arts,basket,ballet,football,gymnastics,rowing,swimming, volleyball or other. These lists of activities were based in published guidelines.16–18 _Moderate _and _vigorous _physical activitiesweredescribedintermsofnumberofactivities,type ofactivitiesandmeandurationofactivitiesperweek.Total timeofmoderateandvigorousphysicalactivityperweekwas computedmultiplyingthedailyamountoftimespentineach activitybyitsweeklyfrequency(i.e.numberofdaysperweek) andthenaddingtheindividualtimeperweekforall activi-tiesreportedbythesameparticipant.Totaltimeofmoderate andvigorousphysicalactivitywasusedtocalculatethe num-berandpercentageofparticipantsreportingatleast420min ofactivity per weekasrecommendin international guide-linesofphysicalactivityforhealthofthoseaged5–17years old(atleast60minofmoderatetovigorousphysicalactivity daily).19

Screenbasedactivities

Screenbasedactivitieswereassessedwith4closedquestions adaptedfromHakalaetal.,20_Students_were_asked_to_report onthenumberofhoursthattheytypicallyspenteachday: (1) WatchingTV/DVDs:usingTVsandDVDstowatchTV

pro-gramsandvideos;

(2) Playing:usingcomputers,TVorPlayStationtoplaywired orstandalonegames;

(3) Usingmobilephones:usingmobilephonesto communi-cateorplay;

(4) Using computers: using desktopor portable computers and tabletsforcommunicatingand managing informa-tion.

Responseoptionsforeachquestionwere:(1)donotuse;(2) use1horlessperday;(3)use2–3hperday;(4)use4–5hper day;and(5)morethan5hperday.Hakalaetal.,20_assessed test-retestreliabilityofthesequestionsusingaKcoefficient andreportedKvaluesbetween0.45and0.65indicatingafair togoodagreementbeyondchance.

Dataanalysis

ThePredictiveAnalyticsSoftwareversion22(PAWSsoftware) (IBM,NewYork)wasusedforstatisticalanalysis.Descriptive statisticswereusedtocharacterizethesampleintermsofage, sex,yearsofformaleducation,physicalactivityand screen time.Meanandstandarddeviation(SD)werereportedfor con-tinuousvariablesandcountandproportionwerereportedfor categoricalvariables.AChi-squaretestwasusedto investi-gate differencesin thedistribution ofboysand girls for(i) attendanceofphysicalactivity classes,(ii)compliancewith international guidelines for physical activity, (iii) type and intensityofphysicalactivityand(iv)timespent(ordinal vari-able)ineachofthefourscreenbasedactivities.Differences betweenboysandgirlsfornumberofphysicalactivitiesand time spentinmoderate andvigorous activitieswere inves-tigatedusinganindependentsamplet-test.Thecorrelation betweentimeperweekspentinphysicalactivityandscreen time was investigated using the Spearman rho correlation coefficientandthestrengthofthecorrelationwasinterpreted aslowifthecoefficientwas<0.3,moderateifitwasbetween 0.3and0.5,andstrongifitwas>0.5.21 _Level_of_significance wassetatp<0.05.

Results

Atotalof969(72.9%)studentsoutofthetotalnumberof stu-dents(n=1330)answeredtheonlinequestionnaire.Ofthese, 502(51.8%)weregirlsand467(48.2%)wereboysranginginage from13to21yearsold(mean±SD=15.6±1.8years).

Physicalactivity

Ofthe969respondents,939(97.0%)reportedtoregularly par-ticipate inthe physical education classes against29 (3.0%) whoreportednottoparticipateintheseclasses(oneresponse missing). Moregirlsthan boysmissthe physicaleducation classes(2₍₁₎₌_9.01,_p₌_0.002).

Regardingmoderatephysicalactivity,714(73.7%) respon-dentsreportedtobeinvolvedinatleastonemoderatephysical activity.Fromthese714students,18(2.5%)didnotreporton theactivity(ies)performed.Oftheremaining696respondents, 304 (43.7%)reported oneactivity only,265 (38.1%)reported 2activities,104(14.9%)reported3activities,20(2.9%)reported 4 activities, 1 (0.01%) reported 5 activities and 2 (0.03%) reported6activities.Themeannumberofmoderateactivities per student was significantly higher for girls (mean±SD= 1.49±1.17) compared to boys (mean±SD=1.23±0.97; p=0.003).Theactivitiesmostreportedwerecycling(n=473, 66.2%) and walking to/from school (n=343, 48.0%). When consideringthedistributionofboysandgirlsperactivity,it was found that more boysthan girls reported cycling and skating and more girls than boys reported roller skating, walking to/from school and walking in general (Table 1). Nevertheless, whenconsideringtotaltimespentin moder-ate physicalactivities, no differences were found between boys and girls (boys: mean±SD=267.94±406.15; girls: mean±SD=211.99±225.22, p=0.25). Table 2 presents total timeperweekspentinmoderatephysicalactivityaswellas totaltimepertypeofactivityforthetotalsample.

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Table1–Typeofphysicalactivityfortheoverallsampleandcomparisonbetweenboysandgirls.

Physicalactivity Number(%) Chi-square

Allrespondents(n=968a₎ _Girls_(n₌_501;_51.8%) _Boys_(n₌_467,_48.2%)

Yes No Yes No Yes No

Physicalactivityclasses 939(97.0) 29(3.0) 478(95.4) 23(4.6) 461(98.7) 6(1.3) 2(1)=9.01,p=0.002 ModeratePAb ₇₁₄_(73.7) ₂₅₄_(26.3) ₃₇₄_(74.7) ₁₂₇_(25.3) ₃₄₀_(72.8) ₁₂₇_(27.2) 2₍₁₎₌_0.43,_p₌_0.559

Cycling 473(66.2) 215(57.5) 258(75.9) 2(1)=26.95,p<0.001

Rollerskating 51(7.1) 37(9.9) 14(4.1) 2(1)=8.96,p=0.003

Skating 82(11.5) 33(8.8) 49(14.4) 2(1)=5.47,p=0.025

Walkingto/fromschool 343(48.0) 213(56.9) 130(38.2) 2(1)=24.99,p<0.001

Walking 235(32.9) 173(46.3) 62(18.2) 2(1)=63.63,p<0.001

Other 59(8.3) 28(7.5) 31(9.1) 2(1)=0.63,p=0.497

Didnotreport 18(2.5)

VigorousPAb ₅₇₅b_(59.4) ₃₉₃_(40.6) ₂₅₃_(50.5) ₂₄₈_(49.5) ₃₂₂_(69.0) ₁₄₅_(31.0) 2₍₁₎₌_34.12,_p_<_0.001 Handball 4(0.7) 2(0.8) 2(0.6) 2(1)=1.33,p=0.515 Running 56(9.7) 30(11.9) 26(8.1) 2(1)=2.31,p=0.156 Martialarts 23(4.0) 6(2.4) 17(5.3) 2(1)=3.12,p=0.089 Basket 78(13.6) 25(9.9) 53(16.5) 2(1)=5.23,p=0.027 Ballet 83(14.4) 80(31.6) 3(0.9) 2(1)=108.04,p<0.001 Football 146(25.4) 16(6.3) 130(40.4) 2(1)=86.70,p<0.001 Gymnastics 29(5.0) 23(9.1) 6(1.8) 2(1)=15.45,p<0.001 Rowing 4(0.7) 1(0.4) 3(0.9) 2(1)=0.59,p=0.634 Swimming 123(21.4) 65(25.7) 58(18.0) 2(1)=4.97,p=0.031 Volleyball 23(4.0) 21(8.3) 2(0.6) 2(1)=21.76,p<0.001 Other 165(28.7) 55(21.7) 110(34.2) 2(1)=10.69,p=0.001

Didnotreport 6(1.0)

PA–physicalactivity.

a _Data_missing_from_one_participant.

b _Percentages_add_up_to_more_than_100%_as_respondents_could_report_on_more_than_one_moderate_and_vigorous_PA.

Table2–Totaltimespentineachtypeofphysicalactivityandinmoderateandvigorousphysicalactivitiesperweek (inminutes).

Physicalactivity n Minimum Maximum Mean±SD

ModeratePA 714 10 4100 244.80±327.07

Cycling 473 10 2100 146.60±221.83

Walkingto/fromschool 343 10 750 92.08±85.04

Walking 235 10 1400 153.64±162.17 Skating 82 10 2160 178.66±323.38 Rollerskating 51 10 450 81.84±88.08 OtherPA 59 15 720 196.64±194.64 VigorousPA 575 20 3120 349.53±306.19 Handball 4 100 480 273.33±192.18 Running 56 20 840 195.45±175.49 Martialarts 23 60 315 158.95±84.93 Basket 78 30 1260 357.73±191.95 Football 146 20 1320 302.19±206.07 Ballet 83 60 630 248.52±162.91 Gymnastics 29 60 540 245.39±132.81 Swimming 123 30 1110 189.79±212.57 Rowing 4 120 240 180.00±84.85 Volleyball 23 40 900 232.11±213.30 OtherPA 165 30 1800 306.06±303.96 Moderate+vigorousPA 832 15 5760 446.35±474.07 PA–physicalactivity.

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Regardingvigorousphysicalactivities,atotalof575(59.4%) respondents reported to participate in these activities. Of the 575 participants, 6 (1.0%) participants did not specify theactivity inwhichtheywere involved. Ofthe remaining 569 participants, 438 (77.0%) reported one vigorous activ-ity, 103 (18.1%) reported 2 activities, 24 (4.2%) reported 3 activities, 2 (0.04%) reported 4 activities and another 2 (0.04%) reported 5 activities. The activities most reported were football(n=146, 25.4%)and swimming(n=123,21.4%) and a high number of participants signaled the response option “Other physical activities” (165, 28.7%). Despite the fact that more boys than girls reported to partici-pate in vigorous physical activities (2₍₁₎₌_34.12, _p_<_0.001),

no significant differences were found in the mean num-ber of vigorous activities per student between genders (boys: mean±SD=1.28±0.57; girls: mean±SD=1.30±0.62; p=0.34). When considering the distribution of boys and girls per activity, more boys than girls reported playing basket,football and other activities, whilemore girls than boysreported ballet, gymnastics, swimming and volleyball (Table1).Inaddition,boysspentmoretimeinvigorous phys-ical activities than girls (boys: mean±SD=381.06±317.45; girls:mean±SD=309.41±286.87,p=0.005).Table2presents totaltimeperweekspentinvigorousphysicalactivityaswell astimepertypeofactivityforthetotalsample.

Atotal of325 (35.3%)participants (from 832valid data) reportedat least420min ofmoderate tovigorous physical activityperweek.Boyswere morelikelythan girlstoreach atleast420minofphysicalactivity(2₍₁₎₌_30.94,_p_<_0.001).

Atotalof128outof969(13.2%)respondentsdidnotreport performingmoderateorvigorousphysicalactivity(inaddition tophysicaleducationclasses).

Screenbasedactivities

Results concerning the use of electronic devices are pre-sented inTable3.Thepercentageofparticipantsreporting nottoperformscreen basedactivitiesvariedbetween5.4% whoreportednotwatchingTV,and11.7%whoreportednot using mobile phones. Aconsiderable percentage of partic-ipants report to spend 4h or more watching TV (11.0%), playing(20.6%),usingmobilephones(30.2%)andusing com-puters(19.6%).Boystend tospendmoretime playingthan girls (2₍₄₎₌_46.6; _p_<_0.001), _while _girls _tend _to _use _mobile

phonesmorethan boys(2₍₄₎₌_45.7,_p_<_0.001). _Respondents

whoreportedtospendmoretimeinonescreenbasedactivity tendtoalsospendmoretimeintheotherscreenbased activ-ities(Table4).Allbut5respondentsreportednottoperform anyofthefourscreenbasedactivitiesenquired.

Associationbetweenphysicalactivityandscreenbased

activities

Nosignificantdifferenceswerefoundbetweenthosereporting moderate or vigorous physical activity and those repor-ting no moderate or vigorous physical activity in terms oftime spentofwatching TV(2₍₄₎₌_4.85, _p₌_0.77), _playing

(2₍₄₎₌_5.83,_p₌_0.67),_using_mobile_phones₍2₍₄₎₌_7.76,_p₌_0.46)

orusingcomputers(2₍₄₎₌_12.05, _p₌_0.15). _When_correlating

the amount of time spent in both moderate and vigorous T

able 3 – Dail y use of electr onic de vices (n = 962 a). Acti vity Do not use ≤ 1 h per da y 2/3 h per da y 4/5 h per da y >5 h per da y Chi-squar e All Girls Bo ys All Girls Bo ys All Girls Bo ys All Girls Bo ys All Girls Bo ys W atc hing TV 52 (5.4) 27 (5.4) 25 (5.4) 404 (41.7) 213 (42.4) 191 (41.3) 399 (41.2) 213 (42.4) 186 (40.3) 72 (7.4) 32 (6.4) 40 (8.7) 35 (3.6) 15 (3.0) 20 (4.3) 2(4) = 3.2 p = 0.52 Pla ying 105 (10.8) 75 (15.0) 30 (6.5) 345 (35.6) 205 (41.0) 140 (30.3) 313 (32.3) 143 (28.6) 170 (36.8) 116 (12.0) 45 (9.0) 71 (15.4) 83 (8.6) 32 (6.4) 51 (11.0) 2(4) = 46.6 p < 0.001 Using mobile phones 113 (11.7) 34 (6.8) 79 (17.1) 361 (37.3) 169 (33.8) 192 (41.6) 195 (20.1) 107 (21.4) 88 (19.0) 105 (10.8) 67 (13.4) 38 (8.2) 188 (19.4) 123 (24.6) 65 (14.1) 2(4) = 45.7 p < 0.001 Using computers 86 (8.9) 37 (7.4) 49 (10.6) 375 (38.7) 193 (38.6) 182 (39.4) 311 (32.1) 168 (33.6) 143 (31.0) 95 (9.8) 50 (10.0) 45 (9.7) 95 (9.8) 52 (10.4) 43 (9.3) 2(4) = 3.6 p = 0.46 a Data missing fr om 7 participants.

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Table4–Correlationbetweendailyuseofdifferent electronicdevices.

Activity Playing Usingmobile

phones

Using computers

WatchingTV 0.29** _0.17** _0.27**

Playing 0.16** _0.41**

Usingmobilephones 0.41**

∗∗ _p_<_0.01.

physicalactivity and theuse ofelectronic devices,asmall butsignificantpositivecorrelationwasfoundbetweenmobile phones and total timespent in moderate physicalactivity (r=0.09,p<0.05),totaltimespentinvigorousphysicalactivity (r=0.13, p<0.05), total time spent in moderate and vigor-ous physicalactivity (r=0.12, p<0.01), time spent in other moderatephysicalactivities(r=0.36,p<0.01),walkingto/from school(r=0.15,p<0.01),basket(r=0.27,p<0.01)and gymnas-tics(r=0.42,p<0.05)(Table5),suggestingthatanincreasein thetimespentinthesephysicalactivitiesisassociatedwith increaseduseofmobilephones.Asignificantnegative associ-ationwasfoundbetweenskatingandwatchingTV/videosor DVDs.

Wheninvestigatingdifferencesinthetimespentinscreen basedactivitiesbetweenthoseperformingatleast420minof moderatetovigorousphysicalactivitiesandthose perform-inglessthan240min,asignificantdifferencewasfoundonly formobile phones (2₍₄₎₌_13.06, _p₌_0.01), _with _those

repor-tinglessphysicalactivityalsoreportinglowermobilephone usage.

Discussion

Ourstudyresultssuggestalackofassociationbetween watch-ing TV, playing and using computers and time spent in moderateorvigorousphysicalactivity.Thislackof associa-tion was presentwhen examiningtheassociation forboth totaltimespentinphysicalactivityandtimespentin indi-vidualmodalitiesofphysicalactivity,withtheexceptionofa lownegativeassociationbetweenskatingand watchingTV. In contrast, a low but significant positive association was foundbetweenmobilephonesusageandtimespentwalking to/fromschoolandingymnasticsandalsobetweenmobile phones usageand totaltime spentinmoderate and vigor-ousphysicalactivity,suggestingthatanincreaseinphysical activity is associatedwithagreater useof mobilephones. Studiesinvestigatingtheassociationbetweenphysical activ-ityandscreenbasedactivitiesreportconflictingresults.Ina 4yearslongitudinalstudyinvolving10856USstudentsaged 10–15yearsold,noassociationwasfoundbetweenchanges intelevisionviewing,orsedentarybehaviorsingeneral,and changesinleisure-timemoderate/vigorousphysicalactivity.12 Incontrast,another2yearslongitudinalstudy10_that exam-inedtherelationshipbetweenchangesintimespentwatching TVandplaying,andfrequencyofleisure-timephysical activ-ityfor4594USstudentsfoundthatadecreaseintimespent watching TVwasassociatedwithanincreaseinfrequency ofleisure-timephysicalactivity.Nevertheless,thecorrelation coefficientsbetweenphysicalactivityandwatchingTVwere smallandvariedbetween−0.11and−0.21.Theseresultsare inlinewiththesignificantnegativeassociationfoundinthe

Table5–Correlationbetweenuseofelectronicdevicesandtimespentinmoderateandvigorousphysicalactivities(in minutes).

Physicalactivity WatchingTV Playing Usingmobilephones Usingcomputers

ModeratePA(n=711) −0.03 −0.02 0.09* _0.03 Cycling(n=471) 0.01 −0.06 −0.007 −0.008 Walkingtoschool(n=342) 0.02 0.08 0.15** _0.10 Walking(n=234) 0.04 0.02 0.21 0.08 Skating(n=82) −0.24* ₋_0.08 _0.10 _0.11 Rollerskating(n=51) −0.08 0.11 0.11 0.10 OthermoderatePA(59) 0.18 0.13 0.36** _0.15 VigorousPA 0.05 −0.05 0.13* _0.03 Handball(n=4)# Running(n=56) −0.12 −0.18 −0.01 −0.22 Martialarts(n=22) 0.14 −0.005 0.12 −0.22 Basket(n=76) 0.15 0.09 0.27* _0.22 Football(n=146) −0.09 0.03 0.12 0.08 Ballet(n=83) 0.06 0.002 0.12 0.11 Gymnastics(n=28) 0.38 0.13 0.42* _0.23 Swimming(n=123) −0.02 0.06 0.10 0.02 Rowing(n=4)# Volleyball(n=21) 0.19 −0.06 0.33 0.28 Others(n=165) 0.006 −0.14 0.14 −0.05

Moderate&vigorousPA −0.03 −0.04 0.12** _0.003

PA–physicalactivity.

∗ _p_<_0.05. ∗∗ _p_<_0.01.

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presentstudybetweentimespentwatchingTVandtimespent skating. Across-sectional study including 200615students aged11–15yearsold from 39 differentcountries inEurope and NorthAmerica found thatthe presence/absence ofan associationbetweenphysicalactivityandscreentimeandthe strengthoftheassociation(whenfound)variedacrosstype ofscreen basedactivity and country.9 _There_were _stronger negative associations between screen-based activities and physicalactivitiesinNorthAmericaandtheNordicEuropean countriesandpositiveornon-significantassociationsforEast andSouthern Europeancountries.Portugal wasnotamong the participating countries. Nevertheless, our study results areinlinewiththefindingsofMelkevicetal.,9_for_the_South EuropeanCountriesandaddtotheirclaimthatstrategiesto decreasesedentarybehaviorsandincreasephysicalactivity needtoconsidereachcountry/regionspecificities.

Inwhatconcernstimespentinmoderatephysical activi-ties,ourfindingsaresimilartotheestimatesofaNorwegian study including 908 children age 11–13 years old, which reportedameantimeofweeklyphysicalactivityof approxi-mately358min.14_In_what_concerns_vigorous_physical_activity, thecrossnationsstudy ofMelkenik9 _including_countries_of the SouthEuropefoundthat adolescents aged11–15years oldspentapproximately124minperweekinvigorous physi-calactivity.Differencesintheageofrespondentsareunlikely tocontributetothedistinctresultsastimespentinphysical activitydecreaseswithage.22_However,_differences_in_the_time periodofphysicalactivityconsideredfordatacollectionmay, atleastpartially,explainthehighermeantimespentin vig-orousphysicalactivitiesfoundinthepresentstudy.Whilein thepresentstudyallactivitiesperformedinboutsof10minor morewereincluded,inthestudyofMelkevik,9_only_activities totalizingatleast60minwereconsidered.Furthermore,the extremelyhighstandarddeviationsfoundinthepresentstudy highlightthewidevariabilityoftypespentinphysical activ-ityamongstudents.Thefindingthatboysspendmoretimein vigorousphysicalactivitieswhencomparedtogirlsisinline withthefindingsofMelkeviketal.,9_{Nevertheless,}_Melkevik etal.,9_reported_that_only_11%_of_girls_and_21%_of_boys_meet theinternationalguidelinesofatleast60minofmoderateto vigorousphysicalactivitydaily,19_while_in_the_present_study thisvalueishigherandreachesapproximately35%.

Aconsiderablepercentageofparticipantsreporttospend 4h or more watching TV (11.0%), playing (20.6%), using mobilephones(30.2%)andusingcomputers(19.6%).A system-aticreview23_analyzing_data_from ₅₃₉_independent_samples reportedthatapproximately28%ofyoungpeoplespendmore than4hdailywatchingTVand18% reportedplayingmore than4hperday.Inlinewiththepresentstudyfindings,boys weremorelikelytoreporthigherlevelsofplayingwhen com-paredtogirls(30%vs.7%,p<0.05),butcontrarytoourstudy findings,boysweresignificantlymorelikelytobehighusers ofTVcomparedtogirls.

Melkeviketal.,9_reported_that_in_South_European_countries, 43%(95%CI=41.49–42.82%)ofstudentsspendmorethan2h dailywatchingTV,17%(95%CI=15.81–16.79)spendmorethan 2hdailyplayingand15%(95%CI=14.91–15.94)spendmore than 2h dailyusing computers. Theseestimates are lower than those foundin the present study wherethe percent-age ofstudents reporting2 ormore hoursin thedifferent

screen-basedactivitiesvariedbetween50.3%and52.9%. Nev-ertheless,astudyin7725Canadianstudentsaged13–17years old,24_reported_that_74%_of_boys_and_59%_of_girls_spent_more than 2hdaily inscreen-based activities. Thesecontrasting resultsmaysuggestthatestimatesofdailyscreentimemay varyacrosscountries/regions,butmayalsobeassociatedwith theconstant evolutionofelectronicdeviceswhichdiversity and availabilitytothegeneralpopulationincreasesrapidly. Similarly,inthepresentstudythepercentageofparticipants reportingnotwatchingTV,playing,usingmobilephonesor computersvariedbetween5.4%and11.7%,whichare lower thanthosereportedbyMelkeviketal.,25_in_a_{cross-national} surveyfrom30differentcountries,includingPortugal.These authorsfoundthat23%ofgirlsand19%ofboysreportedno electronicdevicesusage,butindividualcountryestimatesare notpresented.

Takentogetherwebelievethatthisstudyresultsinformon thephysicalactivitiesandscreenbasedactivitiesinwhich stu-dentsareinvolvedaswellasonthetimetheyspendonthem. Itshowsthatanimportantpercentageofstudentsmaynotbe performingtherecommendeddailydoseofphysicalactivity, highlightingtheneedtocontinuethepromotionofphysical activityamongstudents.Furthermore,itaddstotheexisting studiesthatsuggestthatscreenbasedactivitiesarenot dis-placingphysicalactivityandthatinterventionstargetingeach ofthesefactors(i.e.aimingatincreasingphysicalactivityand decreasingscreenbasedtime)mayneedtopursuedifferent strategies.

Study

limitations

Onelimitationofthisstudyisthatwereliedonself-reported measuresforbothphysicalactivityand screentime,which couldhaveinfluencedtheresultsastheytendtobeless accu-ratethanobjectivemeasures.Furthermore,ourstudyincludes participantsfromaspecificregionofPortugaland,therefore, thegeneralizabilitytothewholecountrymaybelimited. Fac-torssuchasthefamilysocioeconomicstatus,thatseemstobe associatedwithbothphysicalactivityandscreenbasedtime andvaryacrosscountriesandregions,26_were_not_included_in thepresentstudyandshouldbeconsideredinfuturestudies. Inaddition,itwouldhavebeeninterestingtostudythe asso-ciationbetweenphysicalactivityandthetotaltimespentin screenbasedactivitiestounderstandhowitcomparestothe individualassociationbetweenphysicalactivityandthetime spentineachofthefourscreenbasedactivitiesconsideredin thepresentstudy.Nevertheless,thiswasnotpossibledueto theordinalnatureofthisvariable.

Conclusion

Thisstudyfoundnoassociationbetweenplayingandusing computers and physical activity,neither whenconsidering typeofphysicalactivitynorwhen consideringoverall time spentinphysicalactivity.Anegativeassociationwasfound betweenwatchingTVandskatingandapositiveassociation was foundbetweenmobile phonesuse and physical activ-ity.Thesefindingssuggestthatscreentimeisnotdisplacing physicalactivityandthatinterventionsaimingtopromotethe

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increaseofphysicalactivityandthedecreaseofscreentime mayneedtoaddressdifferentfactors.Furtherstudies,both quantitativeandqualitative,areneededtoconfirmandhelp understandthepositiveassociationbetweenmobileuseand physicalactivity.

Conflicts

of

interest

Theauthorshavenoconflictsofinteresttodeclare.

Acknowledgments

Authorswouldliketothankallstudentsthatparticipatedin thestudy,theDirectionofAgrupamentodeEscolasdeÍlhavo, thePhysicalEducationteachersandDr.a_Fernanda_Loureiro

fromtheCentrodeSaúdedeÍlhavo.

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