Sedentary Behaviour, Physical Activity, Physical Fitness and

Subclinical Atherosclerosis in 11-12 Years-old Children

Xavier Melo

, Helena Santa-Clara

, Sandra S. Martins

, Cláudia S. Minderico

Bo Fernhall

and Luís B. Sardinha

Faculty of Human Kinetics, Technical University of Lisbon, CIPER - Exercise and Health Laboratory, Lisbon, Portugal

College of Applied Health Sciences, University of Illinois at Chicago, IL, U.S.A.

Faculty of Physical Education and Sports, Lusofona University, Lisbon, Portugal

Keywords: Atherosclerosis, Children, Muscular Strength, Cardiorespiratory Fitness, Physical Activity, Sedentary

Behaviour, Intima-media Thickness, Common Carotid Artery.

Abstract: Aim: Examine the influence of sedentary behaviour (SED), physical activity (PA), muscular strength (MS)

and cardiorespiratory fitness (CRF) on subclinical atherosclerosis in 11-12 years-old children. Methods: We

assessed intima-media thickness (IMT) of the common carotid artery in 366 children aged 11-12 years-old

(191 girls). Measures included IMT assessed with high-resolution ultrasonography, pulse pressure (PP), a

maximal handgrip strength test, body mass index, waist circumference, body fat mass and lean mass

(LEAN) from DXA and CRF determined using a maximal cycle ergometer test. SED and PA were assessed

by accelerometry. MS was adjusted for LEAN yielding relative MS (RMS). Association between IMT and

RMS adjusted for SED, PA and CRF were tested with multiple linear regression analysis. Differences in

risk factors among RMS groups were tested with ANOVA/ANCOVA. Results: RMS was related to IMT

independently of PA, CRF, age, gender, maturity and PP (p<0.05). As compared with the higher RMS

group, subjects in the lower RMS group had increased body composition phenotypes, hemodynamics and

IMT, and lower moderate-vigorous PA, MS and CRF (p<0.05). Full modelling exposed the detrimental and

independent role of RMS in arterial structure in 11-12 years-old children. Greater RMS is associated with

improved vascular health even in children.

1 INTRODUCTION

Children are not generally considered at risk for

having clinical cardiovascular disease (CVD) events

in the short term. However, the high prevalence of

sedentary behaviour (SED), low cardiorespiratory

fitness (CRF) as well as clustering of cardio-

metabolic risk factors during youth sets the stage for

heart disease in the middle and older ages

(Carnethon et al., 2005); (Sattelmair et al., 2011)

coupled with premature changes in carotid intima-

media thickness (IMT), an intermediate phenotype

for early atherosclerosis and a solid predictor of

future vascular events (Lorenz et al., 2007).

Another important health related component of

fitness is muscular strength (MS) and despite

receiving far less attention than CRF, recent studies

support the hypothesis that low muscular strength in

childhood (Ortega et al., 2012); (Sato et al., 2009),

and adulthood also predicts all-cause mortality, as

well as mortality due to cardiovascular disease and

cancer in healthy and diseased people (Gale et al.,

2007); (Katzmarzyk and Craig, 2002); (Ruiz et al.,

2008).

This study examined the influence of relative MS

(RMS), SED, PA and CRF measures on IMT in 11-

12 years-old children. In addition we examined

whether differences among RMS tertiles translated

to physiologically relevant differences increasing

both metabolic and cardiovascular risk.

2 METHODS

Participants were 366 children (191 girls) aged 11-

12 years-old from 6 schools of the Lisbon district.

Height and sitting height were measured to the

nearest 0.1 cm and body mass was measured to the

nearest 0.1 kg on a scale with an attached

stadiometer (model 770, Seca; Hamburg,

Melo X., Santa-Clara H., S. Martins S., S. Minderico C., Fernhall B. and B. Sardinha L..

Sedentary Behaviour, Physical Activity, Physical Fitness and Subclinical Atherosclerosis in 11-12 Years-old Children.

DOI: 10.5220/0004648100220026

In Proceedings of the International Congress on Cardiovascular Technologies (CARDIOTECHNIX-2013), pages 22-26

ISBN: 978-989-8565-78-5

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

Deutschland). Waist circumference (WC) was

measured to the nearest millimeter with an inelastic

flexible metallic tape (Lufkin - W606PM,

Vancouver, Canada) midway between the lower rib

margin and the iliac crest.

Total-body scans were performed by dual-energy

radiographic absorptiometry (DXA) and analysed

using an extended analysis program for body

composition (Hologic Explorer-W, fan-beam

densitometer, software QDR for windows version

12.4, Waltham, Massachusetts, USA) to determine

body fat mass (BFM), trunk fat mass (TFM) and

lean body mass (LEAN).

Maturity offset was predicted with the equation

of Mirwald et al., (2002).

Physical activity was assessed by accelerometry

(ActiGraph GT1M model; Fort Walton Beach, FL)

during four consecutive days, including two

weekdays and two weekend days (Trost et al., 2005).

MS was measured on the dominant arm using a

highly reliable portable electronic dynamometer

(Jamar, EN-120604, Lafayette Instrument Company,

USA) according to previously published instructions

(De Smet and Vercammen, 2001); (Holm et al.,

2008). The mean effort of 2 attempts (10 s of

contraction with a rest period of at least 60 s) was

used as peak absolute force (MS; kg) and relative

handgrip strength (RMS; kg.kg LEAN

-1

CRF was indirectly determined by a cycle test

with progressively increasing workload using an

electronically braked cycle ergometer (Monark 828

E Ergomedic; Monark, Vansbro, Sweden). Initial

and incremental workloads were 20 W for children

weighing less than 30 kg and 25 W for children

weighing 30 kg or more. The workload was

increased every 3 minutes until the maximal effort

of the participants was reached (Klasson-Heggebø et

al., 2006).

The heart rate at rest (HR

rest

), brachial systolic

blood pressure (SBP) and diastolic blood pressure

(DBP) were measured after 10 min with the

participants in the supine position using an

automated oscillometric cuff (HEM-907-E, Omron,

Tokyo, Japan). Two measurements were taken and if

these values deviated by >5 mmHg, a third

measurement was performed. The pressure

difference between the SBP and DBP (PP) was

calculated for adjustment purposes since SBP and

DBP were positively correlated with the mean IMT

of both the common and internal carotid arteries in a

total of 128 Greek children and adolescents aged 10-

19 yers-old (Stabouli et al., 2012).

The IMT of the common carotid artery (CCA)

was defined as the distance between the leading

edge of the lumen–intima interface to the leading

edge of the media–adventitia interface of the far wall

of the carotid artery. Carotid ultrasound was

performed on the right carotid artery using an

ultrasound scanner equipped with a linear 13 MHz

probe (MyLab One, Esaote, Genova, Italy) and

implemented with a previously validated

radiofrequency-based tracking of arterial wall that

allows a real-time determination of common carotid

far-wall thickness (QIMT®) with high spatial and

temporal resolution (Hoeks et al., 1997).

Multiple linear regression analysis was used to

estimate the association between the exposure

variable (IMT) and PA and physical fitness.

Additionally we categorize subjects in tertils

according to handgrip strength adjusted to LEAN of

the individual (RMS). Hence, lower MS (LRMS):

≤0.65, middle MS (MRMS): >0.65 and <0.75, and

higher MS (HRMS): ≥0.75 differences in strength

and CRF measures were assessed with ANOVA.

LSD test was used for post hoc comparison of means

between each pair of groups. The statistical

significance level was p <0.05.

3 RESULTS

The characteristics of the study group are present in

Table 1.

The determinants of IMT were examined in

multivariate regression analyses in the entire cohort

(Table 2). SED and MVPA were not associated with

IMT (1

model). CRF was the most important

determinant of IMT (2

model) independent of age,

gender and maturity.

Table 1: Means of the basic characteristics of the study

group.

Variables Unit All

Age (years) 11.35

BMI (kg.m

‐2

) 19.46

Maturity (years)‐0.88

rest

(bpm) 89.57

SBP (mmHg) 110.99

DBP (mmHg) 61.69

IMT (mm) 0.50

Abbreviations: SBP: systolic blood pressure; DBP: diastolic

blood pressure; IMT: intima-media thickness of the common

carotid artery.

However, when RMS was added to this model,

CRF was no longer a determinant of IMT over RMS

even when controlled for pulse pressure.

As compared to HRMS group (Table 3), subjects

in the LRMS group had higher mean values of body

SedentaryBehaviour,PhysicalActivity,PhysicalFitnessandSubclinicalAtherosclerosisin11-12Years-oldChildren

mass index (BMI), WC, BFM, SBP, DBP and IMT,

and lower LEAN, maturity offset, MS, moderate-

vigorous PA (MVPA) and CRF (p<0.05).

Table 2: Multiple regression analysis with IMT as

dependent variable and SED, PA, CRF and RMS as

determinants.

IMT Variables Beta SEE P

Model 1 SED -0.01

†

0.23

PA -0.02

†

0.08

Model 2 CRF -0.11 0.82 0.04

Model 3 RMS -0.13 0.82 0.01

CRF -0.08

†

0.16

The models are adjusted for age, gender, maturity and pulse

pressure.

†

Excluded variable.

Abbreviations: RMS: Relative muscular strength; MVPA:

moderate and vigorous physical activity per day; SED: Sedentary

behaviour; CRF: Cardiorespiratory fitness; IMT: intima-media

thickness of the common carotid artery

4 DISCUSSION

Results from this cohort study suggest that RMS is

an independent predictor of intima-media thickness

in 11-12 years-old children. Children with lower

RMS have increased IMT, higher hemodynamic

values, total and abdominal body fatness coupled

with lower MVPA and CRF, apparently setting the

stage for cardiovascular complications in adulthood.

The breakthrough finding from this study was

that IMT, suggested to be predictor of CVD factors

in adults (Lorenz et al., 2007), was associated with

RMS independently of age, gender, maturity, PP,

SED, MVPA and CRF.

These results strengthen up the data from cross-

sectional studies (Artero et al., 2011); (Steene-

Johannessen et al., 2009). The latter, using a cohort

of 9- and 15-yr-old Noregian children (N = 2818),

showed that MS was independently and inversely

associated with clustered metabolic risk after

adjustment for confounding factors.

To what public health policies are concerned, the

evidence provided from our study along with the

findings from the prospective population-based

study of Grøntved et al., (2013) and Grøntved et al.,

(2013) suggesting that greater MS in youth is

associated with lowers levels of CVD risk factors

and a healthy insulin sensitivity and beta-cell

function in young adulthood, independent of CRF

and adiposity, is of particular importance supporting

the inclusion of a specific recommendation for

activities that increase MS as part of the guidelines

for physical activity in youth for primordial

prevention of CVD risk later in life.

Table 3: Means of the characteristics the muscular strength

groups.

Variables Unit LRMS MRMS HRMS

n (n) 122 123 121

Age (years) 11.29 11.37 11.40

Boys/Girls (n) 45/77 67/56 63/58

Weight (Kg) 48.11 44.77 41.55

*#†

Height (cm) 153.19 150.88 149.50

BMI (kg.m

‐2

) 20.36 19.54 18.46

*†

WC (cm) 69.24 66.60 64.17

*#†

BFM (Kg) 14.66 12.23 11.13

LEAN (Kg) 33.21 32.10 30.13

Maturity (years) ‐0.55‐1.01‐1.10

MS (Kg) 19.47 22.42 24.36

*#†

SED (min) 542.18 536.19 525.84

MVPA (min) 45.48 57.40 60.27

Wmax (Watts.

kg‐1

) 2.43 2.75 2.80

rest

(bpm) 91.20 88.28 89.23

max

(bpm) 193.77 195.84 195.25

CRF

(ml.kg

‐1

.min

‐

)

38.99 43.09 44.54



SBP (mmHg) 113.62 110.11 109.24

DBP (mmHg) 62.92 61.68 60.45*

DIAM (mm) 6.28 6.30 6.18

IMT (mm) 0.51 0.50 0.48*

* Significantly differences between LRMS and HRMS (p<0.05;

# Significantly differences between LRMS and MRMS (p<0.05);

† Significantly differences between MRMS and HRMS (p<0.05).

Abbreviations: LRMS: lower relative muscular strength group;

MRMS: middle relative muscular strength group; HRMS: higher

relative muscular strength group; BMI: body mass index; WC:

waist circumference; BFM: body fat mass by DXA; Maturity:

maturity offset; MS: muscular strength; MVPA: moderate and

vigorous physical activity per day; SED: Sedentary behaviour;

Wmax: Maximal power output, HRrest: Heart rate at rest;

HRmax: Heart rate at peak effort; CRF: Cardiorespiratory fitness;

SBP: systolic blood pressure; DBP: diastolic blood pressure;

DIAM: diameter of the common carotid carotid artery; IMT:

intima-media thickness of the common carotid artery.

The differences among groups in fat

accumulation, MVPA, CRF, BP and IMT translate

to physiologically relevant differences increasing

both metabolic and CVD risk. Exercise training

reduces primary and secondary cardiovascular

events, which is, at least partly mediated through the

direct effects on vascular function and structure

(Green et al., 2008).

Intervention studies have provided mixed results

on the ability of exercise training to reverse vascular

function and structure in children. Seeger et al.,

(2011) for example, showed that an 18-week

exercise training program with predominantly

running exercise in children with T1DM (10.9 ± 1.5

years) improved flow-mediated dilation (FMD)

without altering IMT or WC. Woo et al. (2004)

CARDIOTECHNIX2013-InternationalCongressonCardiovascularTechnologies

showed that dietary and/or exercise intervention

programs in 82 overweight children (BMI, 25±3), 9-

12 years-old produced only small changes in IMT

despite a 4.9% change in %BFM and Meyer et al.

(2006) concluded that regular exercise over 6

months restores endothelial function and improves

carotid IMT associated with an improved

cardiovascular risk profile in obese 14.7±2.2 years-

old children.

Yet, the relative risk of both myocardial

infarction and stroke rises with increasing IMT

(Lorenz et al., 2007). Hence, the larger IMT by 0.03

mm (30% of 0.1 mm) in LRMS group compared

with HRMS group in this study may result in a

higher risk of CVD later in life, highlighting the

importance of increasing physical fitness.

Additionally, we can not disregard the fact that

CRF and MS explained 15% of the variability in

cardiovascular health outcomes in a study where

Janz et al., (2002) assessed CRF, MS, vigorous and

sedentary activity, maturation, blood pressure, lipids,

and body composition in 125 healthy children for a

period of five years (mean baseline age, 10.5 years).

The results indicated that maintaining high levels of

CRF and MS during late childhood were associated

with low levels of overall and abdominal adiposity

during adolescence.

Different possibilities exist as to why we did not

observe an association of MVPA with IMT. First,

given the young age of our sample, it is likely that it

has not been exposed to the extent that would affect

the structural measures that could be identified later

in adolescence as in Meyer, et al. (2006) and

Pahkala, et al. (2011). Second, structural adaptations

may occur early in life but are not detectable with

the ultrasound (Virmani et al., 2000).

5 CONCLUSIONS

Full modelling of SED, PA, CRF and RMS exposed

the detrimental role of RMS in arterial structure in

11-12 years-old children. Greater MS for any given

LEAN mass is associated with improved vascular

health even in children.

ACKNOWLEDGEMENTS

The first author of this paper is supported by a

research grant from the Foundation for Science and

Technology (FCT), Ministry of Education and

Science of Portugal (grant: SFRH/ BD/ 70515/

2010).

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CARDIOTECHNIX2013-InternationalCongressonCardiovascularTechnologies