Physical Activity, Fitness, Weight Status, and Cognitive Performancein Adolescents

Jonatan R. Ruiz, PhD, Francisco B. Ortega, PhD, Ruth Castillo, BSc, Miguel Martın-Matillas, PhD, Lydia Kwak, PhD,

German Vicente-Rodrıguez, PhD, Jose Noriega, PhD, Pablo Tercedor, PhD, Michael Sjostrom, MD, PhD,

and Luis A. Moreno, MD, PhD , on behalf of the AVENA Study Group*

Objective To examine the association of participation in physical sports activity during leisure time, sedentary be-haviors, cardiorespiratory and muscular fitness, and weight status with cognitive performance in Spanish adoles-cents.Study design This cross-sectional study comprised a total of 1820 adolescents (958 female) aged 13.0 to 18.5years. Cognitive performance (verbal, numeric and reasoning abilities, and an overall score) was measured with the‘‘SRA-Test of Educational Ability.’’ Participation in physical sports activity during leisure time (yes/no) and time de-voted to study, television viewing, and playing video games were self-reported and categorized as #3 hours/dayand >3 hours/day. We assessed cardiorespiratory and muscular fitness with field-based tests. Adolescents wereclassified as underweight, normal weight, overweight, and obese.Results Participation in physical sports activities during leisure time was associated with better cognitive perfor-mance study variables (all P < .001), independent of potential confounders including cardiorespiratory fitness andbody mass index. We did not observe an association of time devoted to study, television viewing, or playing video-games with cognitive performance. Likewise, cognitive performance was similar across cardiorespiratory and mus-cular fitness levels and body weight categories.Conclusion Participation in physical sports activity during leisure time may positively influence cognitive perfor-mance in adolescents. (J Pediatr 2010;157:917-22).

There is increasing evidence that regular physical activity has positive effects on brain health and that it delays cognitivedecline in adults.1 Whether this effect also apply to young people is not clear. Results from cross-sectional studies in-dicate a positive association between physical activity and academic performance in children.2,3 Findings from interven-

tional studies also show that children in the physical activity intervention group have at least similar academic performancecompared with children in the control group, despite a substantial reduction in time devoted to academics.2,3 Less is known,however, about the association between physical activity and specific cognitive abilities during adolescence, a period of lifewhen the brain has profound plasticity.4

The effect that sedentary behaviors have on cognitive performance is of concern. Increased television viewing time is associ-

From the Department of Medical Physiology, School ofMedicine, University of Granada, Granada, Spain (J.R.,F.O.); Unit for Preventive Nutrition, Department ofBiosciences and Nutrition at NOVUM, KarolinskaInstitutet, Huddinge, Sweden (J.R., F.O, L.K., M.S.);Department of Basic Psychology, School of Psychology,University of Malaga, Malaga, Spain (R.C.); Departmentof Physical Education and Sport, School of SportSciences, University of Granada, Granada, Spain(M.M-M., P.T.); Department of Physiotherapy andNursing, School of Health and Sport Sciences, Universityof Zaragoza, Huesca, Spain (G.V-R.); Department ofPediatrics, University of Cantabria, Santander, Spain(J.N.); and Department of Physiotherapy and Nursing,

ated with worse academic performance in children5-7 and adolescents,8 yet play-ing action video games seems to improve cognitive performance in adults.9-11

Both cardiorespiratory fitness and fatness are considered important healthmarkers already in both children and adolescents.12,13 The association betweenphysical fitness and cognitive performance in adolescents is contradictory.3 Et-nier et al 14 concluded from a meta-analysis that there is no evidence for an as-sociation between cardiorespiratory fitness and cognitive performance in adults,whereas Hillman et al2 provided evidence that cardiorespiratory fitness can havea positive effect on cognitive performance, at least in pre-pubertal children. Theassociation between overweight or obesity and cognitive performance in youth isalso inconclusive.15-19

School of Health Sciences, University of Zaragoza,Zaragoza, Spain (L.M.)

*List of members of the AVENA Study Group available atwww.jpeds.com (Appendix).

Supported by the Spanish Ministry of Health (FIS no 00/0015), the Spanish Ministry of Education (grants EX-2007-1124 and EX-2008-0641), Panrico S.A., MadausS.A., Procter and Gamble S.A, the Swedish Council forWorking Life and Social Research (F.S.), the SwedishHeart-Lung Foundation (20090635), and the SpanishMinistry of Health: Maternal, Child Health and Develop-ment Network (RD08/0072). The authors declare noconflicts of interest.

0022-3476/$ - see front matter. Copyright � 2010 Mosby Inc.

All rights reserved. 10.1016/j.jpeds.2010.06.026

ANCOVA One-way analysis of covariance

AVENA [Alimentacion y Valoracion del Estado Nutricional de los Adolescentes Espanoles]

Food and Assessment of the Nutritional Status of Spanish Adolescents study

BMI Body mass index

CI Confidence interval

OR Odds ratio

SD Standard deviation

TEA Test of Educational Ability

VO2max Maximum oxygen consumption

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Most of the aforementioned studies rely on self-reporteddata of academic performance, and did not control for po-tential confounders such as socioeconomic status and familystructure.20,21 In this study, we examined the association ofparticipation in physical sports activity during leisure time,sedentary behaviors (time devoted to study, television view-ing, and playing videogames), cardiorespiratory and muscu-lar fitness, and weight status with cognitive performance(including verbal, numeric and reasoning abilities, and anoverall score) in Spanish adolescents. We also examined therelationships in the studied lifestyle-related factors and howthese contribute to better understand the lifestyle-cognitiveperformance associations in adolescents.

Methods

Participants were recruited from the AVENA (Alimentaciony Valoracion del Estado Nutricional de los Adolescentes Es-panoles [Food and Assessment of the Nutritional Status ofSpanish Adolescents]) study. The AVENA study is a cross-sectional study that was primarily designed to assess the nu-tritional status of a representative sample of Spanish adoles-cents aged 13.0 to 18.5 years. Data collection took place from2000 to 2002 in 5 Spanish cities (Madrid, Murcia, Granada,Santander, and Zaragoza). The complete methodology ofthe AVENA study has been detailed.22,23 This study includedadolescents with complete data on cognitive performance (n= 1820; 958 female). The study sample did not differ from thecomplete AVENA sample (n = 2894) in any of the demo-graphic variables (all P > .1).

A comprehensive verbal description of the nature and pur-pose of the study was given to the parents, school supervisors,and adolescents. Written consent to participate was re-quested from both parents and adolescents. Adolescentswith a personal history of cardiovascular disease or cognitivedysfunction, who were taking medication at the time of thestudy, or who were pregnant, were excluded. The study pro-tocol was performed in accordance with the ethical standardslaid down in the 1961 Declaration of Helsinki (as revised in2000), and approved by the Review Committee for ResearchInvolving Human Subjects of the Hospital UniversitarioMarques de Valdecilla (Santander, Spain).

We used the Spanish version of the ‘‘SRA Test of Educa-tional Ability’’ (TEA) to assess cognitive performance.24

This questionaire assesses intelligence with 3 basics schoolskills: verbal, numeric, and reasoning. The TEA test batteryprovides 3 complexity levels: level 1 for children aged 8 to12 years, level 2 for children aged 11 to 14 years, and level3 for adolescents aged 14 to 18 years. On the basis of theage range of our sample, we used levels 2 and 3. The psycho-metric properties of level 2 TEA test battery showed an inter-nal consistency reliability of a = 0.78 for the verbalcomponent, a = 0.83 for the numeric component, a = 0.88for the reasoning component, and a = 0.92 for overall cogni-tive performance. For level 3, internal consistency reliabilitywas a = 0.74 for the verbal component, a = 0.87 for the nu-

918

meric component, a = 0.77 for the reasoning component,and a = 0.89 for overall cognitive performance. The TEA bat-tery administration is collective and requires 42 and 27 min-utes for level 2 and 3, respectively.

Verbal ability assesses command of language, verbal iden-tification, and vocabulary; numeric ability assesses speed andprecision in performing operations with numbers and quan-titative concepts; and reasoning ability assesses logical ordi-nation criteria in sets of figures, numbers, or letters. Directscores (range, 0-33) were obtained for each of these variables,and we also computed an overall cognitive performance vari-able by summing the individual scores of the 3 items (range,0-99).

The adolescents answered the following question: ‘‘Do youpractice any type of physical sports activity outside the schooltime?’’ The possible answers were yes (coded as 1) or no(coded as 0).

We obtained the information about time devoted to studyand time spent in television viewing and playing video gamesfrom the following questions: ‘‘How many hours a day doyou do homework or study?’’ ‘‘How many hours a day doyou watch television?’’ and ‘‘How many hours a day do youplay videogames?’’ Possible answers were 0 = none, 1 = <30minutes, 2 = <1 hour, 3 = 1 to 3 hours, 4 = >3 to 4 hours,5 = >4 hours. Because of the relatively small sample size ineach single category, we re-coded the variables in two cate-gories: 0 when #3 hours/day and 1 when >3 hours/day.25

We assessed cardiorespiratory fitness with the 20-minuteshuttle run test. The score was considered as the number ofstages completed (precision of 0.5 stage). We estimated max-imal oxygen consumption (VO2max) (mLO2/kg/min) withthe equation reported by Leger.26 Adolescents were classifiedin two levels (ie, meeting/not meeting the cardiorespiratoryfitness standards) on the basis of the FITNESSGRAM stan-dards for Healthy Fitness Zone.27 The FITNESSGRAM stan-dards are associated with cardiovascular disease risk factorsin children and adolescents,28,29 and it would be of clinicaland public health importance to understand whether theyare also associated with cognitive performance. This test isvalid and reliable in young people.30,31

Upper body muscular strength was assessed by means ofthe handgrip strength test. The test was performed on bothhands with a hand dynamometer (Takei TKK 5101 Grip-D;Takey, Tokyo, Japan), standing and with the arm completelyextended. The test was performed twice, and the best scorewas retained (in kg). The sum of the right and left handwas used in the analysis.

Lower body muscular strength was assessed by means of thestanding long jump test. The participants were instructed topush off vigorously and jump as far forward as possible, tryingto land on both feet. The distance from the takeoff line to thepoint where the back of the heel closest to the take-off linelanded on the floor was scored. The result was recorded incentimeters. The test was performed twice, and the best scorewas retained. Adolescents were classified in two levels accord-ing to their upper and lower body muscular strength levels asbelow (low) and above (high) the median. The handgrip

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strength and stranding long jump tests are valid and reliablefield-based tests in children and adolescents.30-32

Weight and height were measured following standardizedprocedures, and body mass index (BMI) was calculated asweight in kilograms divided by square of height in meters(kg/m2). BMI was used as a surrogate marker of total bodyfat. Adolescents were classified according to the BMI interna-tional cutoff values as underweight, normal weight, over-weight, and obese.33,34

Parents completed a questionnaire that addressed the ad-olescents’ earlier and current health status and socioeco-nomic status defined as the educational level andoccupation of the father. According to this information,and following the recommendation of the Spanish Societyfor Epidemiology, the adolescents were classified in 5 cate-gories of socioeconomic status: low (I), medium-low (II),medium (III), medium-high (IV), and high (V). We also ob-tained information on maternal education level (primary,secondary, or university). There is evidence indicating thatsocioeconomic status is one of the most important determi-nants of childhood cognitive performance.20

We obtained information about family structure throughthe aforementioned questionnaire. Family structure was de-fined as living with parents or any other arrangement (onlymother, only father, grandparents, others). Family structuremay positively influence adolescents’ cognitive perfor-mance.21

We assessed pubertal development according to Tannerand Whitehouse.35 Self-reported breast development in girlsand genital development in boys was used for pubertal stageclassification.

Statistical AnalysisData are presented as means and SDs, unless otherwise indi-cated. Analyses were performed with the Statistical Packagefor Social Sciences software version 16.0 for Windows(SPSS, Chicago, Illinois) and the level of significance wasset to 0.05.

We analyzed the differences in cognitive performance (in-cluding verbal, numeric, and reasoning abilities and an over-all score) between adolescents who participated in physicalsports activity and adolescents who did not with one-wayanalysis of covariance (ANCOVA) after adjusting for ageand pubertal status (model 1). We performed a second model

Table I. Cognitive performance by participation in physical s

Model 1

Yes (n = 1053) No (n = 506) P Cohen’s d

Overall cognitiveperformance (0-99)

54.7 (13.0) 50.1 (13.5) <.001 0.32 (0.22

Verbal ability (0-33) 21.4 (6.5) 19.8 (6.7) <.001 0.25 (0.15Numeric ability (0-33) 14.6 (3.2) 13.1 (4.5) <.001 0.29 (0.19Reasoning ability (0-33) 18.6 (6.5) 17.2 (6.7) <.001 0.26 (0.16

Values are means (SD).Covariates model 1: sex, age, and pubertal status.Covariates model 2: model 1 plus socioeconomic status and family structure.

Physical Activity, Fitness, Weight Status, and Cognitive Performa

further including socioeconomic status and family structureas co-variates (model 2). We repeated the same model for theother exposures (ie, watching television, playing videogames,and time devoted to study #3 hours/day versus >3 hours/day), cardiorespiratory and muscular fitness (low versushigh), and weigh status (underweight, normal weight, over-weight, and obese). Because we did not observe an interac-tion effect between sex * exposure variables and cognitiveperformance (all P > .2), all the analyses were performedwith boys and girls together and sex was included in the anal-yses as a co-variate. We performed separate models for eachmain exposure, and sex, age and pubertal status were alwaysretained as co-variates (in model 1), whereas socioeconomicstatus and family structure were additionally included as co-variates in model 2.

We also analyzed the associations in exposures with binarylogistic regression analysis. Further, we determined the dif-ferences in cardiorespiratory fitness, muscular strength, andBMI among adolescents who participated in physical sportsactivity, those who did not, and those spending >3 hours/day watching television or playing videogames with AN-COVA. All the models included sex, age, and pubertal statusas co-variates.

We calculated the effect size statistics as Cohen d (stan-dardized mean differences) and 95% CI.36 Values of d equalto 0.2, 0.5, and 0.8 are considered small, medium, and largeeffects, respectively.

Results

Adolescents engaged in physical sports activities during leisuretime had significantly better cognitive performance that thosewho were not (Table I, model 1). The effect size, as determinedwith Cohen d, ranged from 0.25 (verbal ability) to 0.32 (overallcognitive performance). The results did not change whensocioeconomic status and family structure were entered inthe model (Table I, model 2). Further adjustments forcardiorespiratory fitness, BMI, and television viewing (orvideo games or time devoted to study) did not materiallymodify the results (data not shown). Similarly, whenmaternal educational status was used instead ofsocioeconomic status, the findings remained unaltered.

We did not observe an association of time devoted to study,television viewing, or playing videogames with cognitive

ports activity during leisure time in adolescents

Model 2

(95% CI) Yes (n = 817) No (n = 393) P Cohen’s d (95% CI)

1-0.421) 55.0 (14.3) 51.4 (13.9) <.001 0.25 (0.139-0.365)

3-0.353) 21.5 (5.7) 20.4 (5.9) .006 0.18 (0.063-0.289)1-0.391) 14.8 (5.7) 13.3 (5.8) <.001 0.27 (0.153-0.380)0-0.360) 18.8 (5.6) 17.7 (5.7) .003 0.19 (0.076-0.303)

nce in Adolescents 919

Table II. Cognitive performance and sedentary behaviors in adolescents

Model 1 Model 2

£3 hours/day >3 hours/day P £ 3 hours/day <3 hours/day P

Study (n = 1207) (n = 353) (n = 928) (n = 290)Overall cognitive performance (0-99) 53.3 (13.9) 53.3 (14.3) .969 54.1 (13.7) 53.6 (13.8) .599

Verbal ability (0-33) 20.8 (6.3) 21.2 (6.2) .325 21.1 (6.1) 21.2 (6.1) .711Numeric ability (0-33) 14.1 (4.9) 14.0 (5.1) .568 14.3 (4.9) 14.1 (4.9) .441Reasoning ability (0-33) 18.3 (5.6) 18.1 (5.6) .632 18.6 (5.5) 18.2 (5.6) .307

Television viewing (n = 1392) (n = 177) (n = 1096) (n = 125)Overall cognitive performance 53.3 (13.8) 52.1 (13.3) .255 53.8 (13.6) 54.7 (13.8) .510

Verbal ability 20.9 (6.0) 20.5 (6.3) .341 21.1 (6.0) 21.4 (6.1) .643Numeric ability 14.1 (4.9) 13.8 (4.9) .484 14.2 (4.6) 14.6 (4.9) .457Reasoning ability 18.3 (5.6) 17.8 (5.7) .244 18.5 (5.6) 18.7 (5.6) .651

Playing videogames (n = 1483) (n = 85) (n = 1161) (n = 61)Overall cognitive performance 53.4 (13.9) 51.3 (14.2) .194 53.9 (13.6) 54.7 (13.9) .648

Verbal ability 20.9 (6.2) 20.1 (6.3) .218 21.1 (6.1) 21.0 (6.2) .856Numeric ability 14.1 (5.0) 13.4 (5.0) .208 14.3 (4.8) 14.7 (4.9) .534Reasoning ability 18.3 (5.4) 17.8 (5.7) .447 18.5 (5.5) 19.1 (5.6) .439

Covariates model 1: sex, age and pubertal status.Covariates model 2: model 1 plus socioeconomic status and family structure.

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performance (Table II). Likewise, cardiorespiratory fitnesswas not associated with cognitive performance (Figure 1;available at www.jpeds.com). The results did not materiallychange when we used a different equation to estimatecardiorespiratory fitness (VO2max).37 Neither upper bodynor lower body muscular strength were associated withcognitive performance (Figures 2 and 3; available at www.jpeds.com), and the results persisted after we repeated theanalysis comparing the upper and lower sex- and age-specific quintiles (data not shown). Cognitive performancewas similar across weight status categories (Figure 4;available at www.jpeds.com).

We did not observe an association between physical sportsactivity and time devoted to study (odds ratio [OR], 0.818;95% CI, 0.630-1.064). Participation in physical sports activityduring leisure time was associated with a lower OR of watch-ing television for >3 hours/day (0.631; 95% CI, 0.445-0.894)and playing videogames for >3 hours/day (0.533; 95% CI,0.320-0.887). Adolescents participating in physical sports ac-tivity had better cardiorespiratory and muscular fitness levelscompared with those who did not for cardiorespiratory fit-ness (5.9 � 2.0 versus 4.9 � 1.9 stages, respectively; P <.001), standing long jump (177 � 31 versus 154 � 28 cm, re-spectively; P < .001), and handgrip strength (61.1 � 0.4 ver-sus 59.6 � 0.5 cm, respectively; P = .023). BMI did not differin physical sports activity categories (P = .606).

Adolescents who spent >3 hours/day watching televisiontended to have a lower OR of spending >3 hours/day study-ing (0.629; 95% CI, 0.384-1.029). Adolescents who spent <3hours/day playing video games had a significantly lower ORof spending >3 hours/day studying (0.375; 95% CI, 0.147-0.959).

Levels of cardiorespiratory fitness were lower in adoles-cents who spent >3 hours/day watching television comparedwith adolescents who spent #3 hours/day watching televi-sion (4.9 � 1.3 versus 5.6 � 2.1 stages, respectively; P <.001) and so were standing long jump levels (162� 31 versus169 � 32 cm, respectively; P = .019). BMI was higher in ad-

920

olescents who spent >3 hours/day watching television com-pared with those who spent #3 hours/day (22.4 � 3.4versus 21.5 � 3.2 kg/m2, respectively; P = .002), regardlessof sex, age, and puberty stage.

Adolescents who played videogames for >3 hours/day hadlower cardiorespiratory fitness compared with their peerswho spent #3 hours/day (4.5 � 1.0 versus 5.6 � 2.2 stages,respectively; P < .001). The results were similar when we re-peated all the analyses in boys and girls separately.

Discussion

Although no conclusion can be drawn from this cross-sectionalstudy about whether participation in physical sports activityduring leisure time leads to improvements in cognitive perfor-mance in adolescents, these findings are of public health andclinical interest and extend earlier results that suggested the po-tential benefit of physical activity on cognitive performance al-ready in youth.2,3 Adolescence is a period of life when the brainhas profound plasticity because of changes in both structureand function.4 Therefore, the pubertal period offers high pos-sibilities of stimulating cognitive function.4

The relationship between participation in physical sportsactivity and cognitive performance has been a subject of dis-cussion between advocates and skeptics of physical sports ac-tivity, and especially in parents concerned about decreases instudy and homework time. The assumption is based on theparticipation in physical sports activity may ‘‘displace’’ timethat would normally be spent doing schoolwork, readingfor pleasure, or engaging in other educational activities. Inthis study, we observed that participation in physical sportsactivity is not associated with lower time devoted to study.This concurs with intervention studies that indicated thatchildren enrolled in more physical sports activity do nothave poorer academic performance, despite a reduction intime in the so-called ‘‘academic subjects.’’3 Furthermore,we also observed that participation in physical sports activitywas associated with lower television viewing and time

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December 2010 ORIGINAL ARTICLES

devoted to play video games and with higher levels of cardio-respiratory and muscular fitness. This suggest that physicalsports activity may indirectly prevent the deleterious effectsascribed to sedentary behaviors39, 40 and may have an indirectpositive effect on health through its effect on fitness. Findingsfrom intervention studies also reported a positive effect onfitness besides the aforementioned effects on academic per-formance.3 Even single bouts of physical activity (20 minutesof aerobic exercise at 60% of estimated maximum heart rate)may improve cognitive control and attention in children.41

Collectively, these findings are particularly important be-cause of the existing pressure on children and adolescents,parents, and schools to maximize academic performance.We do not know whether sports participation is a markerof adolescents who are high achievers and who do better inthis type of cognitive tests. Moreover, whether adolescentswho persist in sports activity have other characteristics thatallow them to perform well on cognitive tests remains to beelucidated.

There is increasing concern about the amount of time thatyouth spend watching television or playing video games be-cause of the potential effect they may have on health. Indeed,we observed that both television viewing and playing videogames had a negative effect on cardiorespiratory fitness, lowerbody muscular strength, and BMI. Several studies reported anassociation between increased television viewing and decreasedtime spent reading and doing homework,42,43 which inturn may affect academic performance. Results from cross-sectional and longitudinal studies reported that increasedtelevision time had a detrimental impact on academic perfor-mance in children5-7 and self-reported academic performancein adolescents.8 We observed that adolescents who spent moretime watching television or playing video games devoted lesstime to study, which concurs with the so called ‘‘displacementhypothesis.’’44 However, despite this observation, we did notobserve an association between television time and cognitiveperformance. Our data do not concur with experimental stud-ies showing that playing action video games improve cognitiveperformance in young adults.9,10 Differences in the outcomevariable, the participants’ age, and the study design make com-parisons between studies difficult.

Cardiorespiratory fitness is strongly linked to cardiovascu-lar disease risk factors in youth.12,13 Whether it is also associ-ated with cognitive performance is, however, debated. Theconclusion from a meta-regression analysis was that cardio-respiratory fitness was not associated with cognitive perfor-mance in adults,14 which concur with our results, whereasother studies suggested the opposite in children.2 Hillmanand co-workers showed in a series of studies that high cardio-respiratory fitness was associated with better cognition inpre-adolescent children.19,45,46 Several studies hypothesizedthat aerobic fitness may mediate the relationship betweenphysical activity and cognitive performance,47 whereas otherstudies argued that cardiorespiratory fitness is a ‘‘‘gross’’measure of the physiological status and therefore might notbe sensitive enough for one to see any association with cog-nitive performance.14 The association between physical

Physical Activity, Fitness, Weight Status, and Cognitive Performa

sports activity and cognitive performance observed in thisstudy persisted after further adjusting for either cardiorespi-ratory or muscular fitness. Whether more precise measure-ments of both cardiorespiratory fitness (ie, directlymeasured maximum oxygen consumption) and cognitivefunction (eg, electroencephalogram, neuroelectric activity)would yield to a different results in adolescents remains tobe investigated.45 We did not observe an association betweenmuscular fitness and cognitive performance, which concurwith the results observed by other authors.19

A limited number of studies have examined whether in-creased body weight per se is associated with poorer cognitiveperformance.15-19 We did not observe an association betweenweight status and cognitive performance, which concurs withother studies.17,18 Overweight children and adolescents havelower cognitive performance than normal-weight ones afteradjusting for a number of potential confounders.16 Mo-suwan et al17 observed an association between overweightstatus and poor academic performance in children, but notin adolescents. Severely obese Chinese children had signifi-cantly lower intelligence quotient than the control subjects.15

Children with higher cognitive function in early life can be atdecreased risk of overweight years later.48

Limitations of this study include its cross-sectional design,which precludes drawing conclusions on the direction of theassociations. A second limitation relies on the use of a self-reported measure of physical sports activity. Moreover, thisstudy focused only on sports-related activity, and therefore,the duration of the participation and other leisure time phys-ical activity was not recorded. Further research should usephysical activity assessed with objective measures such as ac-celerometry. We did not have data on watching televisionduring weekends, which limited the analysis. We also didnot ask what kinds of video games adolescents play. Strengthsof this study include the use of a relatively large national sam-ple, the inclusion of several potential confounders, and theuse of an objective and standardized measure of cognitiveperformance.

Because cognitive performance is potentially modifiableduring the pubertal phase,4 it would be of interest to investi-gate whether targeted physical activity interventions espe-cially on individuals with cognitive impairment mightinfluence cognitive performance during adolescence andlater in life. n

Submitted for publication Feb 16, 2010; last revision received Apr 30, 2010;

accepted Jun 16, 2010.

Reprint requests: Jonatan R. Ruiz, PhD. Department of Biosciences and

Nutrition, Unit for Preventive Nutrition, Karolinska Institutet, Stockholm,

Sweden, Halsovagen 7-9, SE-141 57 Huddinge, Sweden. E-mail: ruizj@ugr.es.

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Appendix

Members of the AVENA Study Group: Coordinator: A.Marcos, Madrid; principal researchers: M.J. Castillo, Gran-ada; A. Marcos, Madrid; S. Zamora, Murcia; M. GarcıaFuentes, Santander; M Bueno, Zaragoza.

Granada: M.J. Castillo, M.D. Cano, R. Sola (biochemistry),A. Gutierrez, J.L. Mesa, J. Ruiz (physical fitness), M. Delgado,P. Tercedor, P. Chillon (physical activity), F.B. Ortega, M.Martın, F. Carreno, G.V. Rodrıguez, R. Castillo and F.Arellano (collaborators), Dpto Fisiologıa, Universidad deGranada, E-18071 Granada; Madrid: A. Marcos, M. Gonza-lez-Gross, J. Warnberg, S. Medina, F. Sanchez Muniz, E.Nova, A. Montero, B. de la Rosa, S. Gomez, S. Samartın, J.Romeo, R. Alvarez (coordination, immunology), A. Alvarez(cytometric analysis), L. Barrios (statistical analysis), A.Leyva, B. Paya (psychological assessment), L. Martınez, E.Ramos, R. Ortiz and A. Urzanqui (collaborators), Institutode Nutricion y Bromatologıa, Consejo Superior de Investiga-ciones Cientıficas (CSIC), E-28040 Madrid; Murcia: S. Za-mora, M. Garaulet, F. Perez-Llamas, J.C. Baraza, J.F.Marın, F. Perez de Heredia, M.A. Fernandez, C. Gonzalez,R. Garcıa, C. Torralba, E. Donat, E. Morales, M.D. Garcıa,J.A. Martınez, J.J. Hernandez, A. Asensio, F.J. Plaza andM.J. Lopez (diet analysis), Dpto Fisiologıa, Universidad deMurcia, E-30100 Murcia; Santander: M. Garcıa Fuentes, D.Gonzalez-Lamuno, P. de Rufino, R. Perez-Prieto, D. Fernan-dez and T. Amigo (genetic study), Dpto Pediatrıa, Universi-dad de Cantabria, E- 19003 Santander; Zaragoza: M. Bueno,L.A. Moreno, A .Sarria, J. Fleta, G. Rodrıguez, C.M. Gil, M.I.Mesana, J.A. Casajus, V. Blay and M.G. Blay (anthropometricassessment), Escuela Universitaria de Ciencias de la Salud,Universidad de Zaragoza, E-50009 Zaragoza.

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Figure 1. Cognitive performance by cardiorespiratory fitness categories in adolescents. Values are means and SDs. Cut-offpoints are based on the FITNESSGRAM standards for Healthy Fitness Zone.

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Figure 2. Cognitive performance by upper body muscular strength (handgrip strength) categories in adolescents. Values aremeans and SDs. Low and high levels correspond to below and above the median, respectively.

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Figure 3. Cognitive performance by lower body muscular strength (standing broad jump) categories in adolescents. Values aremeans and SDs. Low and high levels correspond to below and above the median, respectively. Cohen’s d = 0.19 (95% CI, 0.080-0.296) for numeric ability.

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Figure 4. Cognitive performance by BMI categories in adolescents. Analyses are adjusted for sex, age, pubertal status, so-cioeconomic status, and family structure. Values are means and SDs.

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