University of Groningen Movement, cognition and underlying brain functioning in children van der Fels, Irene

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Movement, cognition and underlying brain functioning in children

van der Fels, Irene

DOI:

10.33612/diss.109737306

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Publication date: 2020

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van der Fels, I. (2020). Movement, cognition and underlying brain functioning in children. Rijksuniversiteit Groningen. https://doi.org/10.33612/diss.109737306

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6

Eff ects of aerobic and cognitively engaging

physical activity on cardiovascular fi tness and

gross motor skills in primary school children:

A cluster randomized controlled trial

Irene M.J. van der Felsa_{, Esther Hartman}a_{, Roel J. Bosker}b,c_{, Johannes W. de Greeff}a_, Anne G.M. de Bruijnb_{, Anna Meijer}d_{, Jaap Oosterlaan}d,e_{, Joanne Smith}a_{, Chris Visscher}a

a_{University of Groningen, University Medical Center Groningen,} Center for Human Movement Sciences, The Netherlands b_{University of Groningen, Groningen Institute for Educational Research, The Netherlands} c_{University of Groningen, Faculty of Behavioral and Social Sciences,}

Department of Educational Sciences, The Netherlands d_{Vrije Universiteit, Clinical Neuropsychology Section, The Netherlands} e_{Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam and Vrije Universiteit}

Amsterdam, Emma Neuroscience Group, department of Pediatrics, Amsterdam Reproduction & Development, The Netherlands

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Abstract

The aim was to examine the effects of two interventions on cardiovascular fitness and gross motor skills, and whether these effects are influenced by baseline levels, and the dose of moderate-to-vigorous physical activity. A cluster randomized controlled trial was implemented in 22 primary schools (n = 891 children; 7.4 ± 0.7 years). Intervention groups received aerobic or cognitively engaging physical activity (14 weeks, four lessons per week). Control groups followed their regular physical education program. Cardiovascular fitness (20- meter Shuttle Run Test), gross motor skills (Korper Koordinationstest für Kinder and Bruininks-Oseretsky Test of Motor Proficiency - 2nd Edition) and moderate-to-vigorous physical activity (MVPA; measured during the lessons with accelerometers) were assessed. Multilevel analysis showed no main effect of the interventions on cardiovascular fitness and gross motor skills. Interaction effects for cardiovascular fitness showed that children with lower baseline improved more after cognitively engaging physical activity than aerobic physical activity, while children with higher baseline improved more after aerobic physical activity than cognitively engaging physical activity or control condition. A higher dose of MVPA led to higher cardiovascular fitness after both interventions and enhanced gross motor skills after the cognitively engaging intervention. Individual exposure to MVPA and variability in baseline cardiovascular fitness are important factors that influence the effectiveness of interventions.

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125

Introduction

Cardiovascular fi tness and gross motor skills are important indicators for children’s physical health and development. Cardiovascular fi tness is defi ned as the ability of the circulatory and respiratory systems to supply oxygen during sustained physical activity (Corbin, Pangrazi, & Franks, 2000). Low cardiovascular fi tness levels have shown to be related to cardiovascular disease risk factors, increased body fatness, and hypertension (Ortega, Ruiz, Castillo, & Sjöström, 2008). Gross motor skills represent the involvement of large body muscles in balance, limbs and trunk movements (Bishop, 2014). Gross motor skills acquired during early childhood form the basis for advanced movements and sport-specifi c skills as well as for a physically active lifestyle (Clark & Metcalfe, 2002). Unfortunately, signifi cant declines in cardiovascular fi tness and gross motor skills have been shown in children since the 1980s (Runhaar et al., 2010; Timmermans et al., 2017; Tomkinson, Lang, & Tremblay, 2017). Therefore, there is a need for interventions that stimulate both cardiovascular fi tness and gross motor skills.

Primary schools are ideal environments to implement interventions (Gallotta et al., 2015) since more than 90% of children worldwide attend primary school (UNESCO, 2018). Several studies have investigated the eff ects of school-based interventions separately for cardiovascular fi tness and gross motor skills. Meta-analyses showed strong evidence for eff ects of school-based physical activity interventions on cardiovascular fi tness (80% of large higher-quality RCTs were eff ective) and gross motor skills (standardized mean diff erence = 1.42, p < 0.01) in children (Morgan et al., 2013; Sun et al., 2013). However, high variability among the studies included regarding the dose of physical activity (e.g. duration, frequency, and intensity) and the type of activity was demonstrated, which makes it diffi cult to determine the intervention characteristics that are related to the eff ectiveness of interventions. In addition, the eff ects of interventions are infl uenced by characteristics of children, such as baseline levels or the individual amount of physical activity during interventions (Pesce, 2009).

One characteristic that seems important to enhance cardiovascular fi tness is physical activity at moderate-to-vigorous intensity (MVPA). School-based physical activity, such as physical education, provides an opportunity for children to engage in MVPA. A meta-analysis by Hollis et al. (2016) showed that children exercise on average 45% of the total time in MVPA during physical education lessons, although percentages varied between studies (ranging from 11% to 89%). The meta-analysis by Lonsdale et al. (2013) showed that levels of MVPA during physical education can be increased by interventions focusing on high-intensity activities. Therefore, an increase in the number of physical education lessons per week and intervention strategies focusing on high-intensity activities enhance the amount of MVPA and this can subsequently lead to higher cardiovascular fi tness.

Gross motor skills can be improved by activities in which children could repeatedly practice and develop gross motor skills in several ways (McKenzie, 2007). Individual activities, such as coordinative exercises, yield opportunities to learn gross motor skills. Team games provide opportunities to apply gross motor skills in a competitive and strategic way (Best, 2010). Such

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126

games are cognitively engaging, which is defined as “the degree to which the allocation of attentional resources and cognitive effort is needed to master difficult skills” (Tomporowski, McCullick, & Pesce, 2015a). The combination of individual activities to practice gross motor skills and cognitively engaging games to apply gross motor skills in complex situations might enhance gross motor skills in children. Although positive effects of cognitively engaging physical activity have been found for cardiovascular fitness (Schmidt, Jäger, Egger, Roebers, & Conzelmann, 2015b), no studies have examined the effects of cognitively engaging physical activity on gross motor skills.

In the current study, an aerobic intervention - with the aim to increase the amount of MVPA - and a cognitively engaging intervention - with the aim to increase the amount of motor skill challenges - were developed and implemented in 14 weeks of primary school physical education. The two intervention programs were performed four times per week, instead of the regular physical education lessons provided twice per week. The study had three aims. The first aim was to investigate the main effects of the aerobic intervention and the cognitively engaging intervention on cardiovascular fitness and gross motor skills. It was hypothesized that: i) both interventions would enhance cardiovascular fitness and gross motor skills due to the increased frequency of physical education; ii) the aerobic intervention would lead to higher cardiovascular fitness levels than the cognitively engaging intervention, due to the higher dose of MVPA delivered; and iii) the cognitively engaging intervention would lead to better gross motor skills compared to the aerobic intervention, due to presence of more motor skill challenges in the cognitively engaging intervention. The second aim was to investigate whether intervention effects were dependent on baseline cardiovascular fitness and gross motor skills. It was expected that children with lower baseline levels would have greater potential for improvement and therefore would benefit more from the interventions compared to children with higher baseline levels (Kristensen et al., 2010; Logan, Robinson, Wilson, & Lucas, 2012). The final aim was to investigate whether there was a dose-response effect of the total dose of MVPA during the interventions on cardiovascular fitness and gross motor skills. It was expected that children with a higher dose of MVPA during the interventions would be more involved in the lessons and therefore show more improvement in cardiovascular fitness and gross motor skills.

Methods Participants

This study was part of a cluster randomized controlled trial in the Netherlands (“Learning by Moving”), assessing the effects of two interventions on physical and cognitive outcomes, academic achievement, brain structure, and brain functioning in primary school children. A cluster power analysis with 0.40 as effect size (Davis et al., 2011a) resulted in a required sample of ≥ 40 classes (grades three and four) across 20 schools (average cluster size = 25; power = 0.80; α = 0.05; 1-tailed; intraclass correlation = 0.10; Spybrook et al., 2011). To take into account the possibility that schools might withdraw from participation, third and fourth grade children from 24 schools were included in the study. Cluster-randomization was performed in two steps. Firstly,

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127 pairs of schools were made based on the school size and it was randomly determined which intervention a pair of schools received. Secondly, it was randomly determined within the fi rst school of the pair which class (third or fourth grade) received the intervention and which class served as the control group. The other school in the pair received the same intervention, but in the opposite grade class.

Just before the start of the study, two schools withdrew permission, due to organizational diffi culties. Finally, children from grade three and four classes across the 22 primary schools were recruited for the study. School directors and parents or guardians of 891 children gave written consent for their children to participate. Figure 1 shows the total number of children in each stage of the study and for each outcome variable. Reasons for missing values were school absence on testing days, moving to another school, or injuries. This study was approved by the ethical board of the Vrije Universiteit Amsterdam (VCWE-S-15-00197), and registered in the Netherlands Trial Register (NL5194).

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128

Posttest

Baseline

24 primary schools Grade 3 and grade

4

Cluster randomization

Aerobic physical activity (n = 12 classes)

Lost after randomization

n = 1 class

Control group (n = 24 classes)

n = 2 classes

Cognitively engaging physical activity (n = 12 classes)

n = 1 class

Cardiovascular fitness

n = 11 classes, n = 195 children

Gross motor skills

Allocation

Enrollment

Analysis

Aerobic physical activity

n = 11 classes, n = 221 children Cognitively engaging physical activity

Control group

n = 22 classes, 430 children

Figure 1. Flow chart with the number of children in each stage of the study. Figure 1. Flow chart with the number of children in each stage of the study.

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129

Instruments

Cardiovascular fi tness and gross motor skills

Cardiovascular fi tness was measured using the 20-meter Shuttle Run Test (20-m SRT; Adam, Klissouras, Ravazzolo, Renson, & Tuxworth, 1988). Validity and reliability of the 20-m SRT have shown to be adequate in children (Leger, Mercier, Gadoury, & Lambert, 1988). Gross motor skills were assessed using three subtests (jumping sideways, moving sideways, and backwards balancing) of the Körper Koordinationstest für Kinder (KTK; Kiphard & Schilling, 2007). The KTK originally consists of four subtests, but a recent study has shown substantial agreement between three subtests and the original four subtests (Novak et al., 2017). Additionally, one item of the Bruininks- Oseretsky Test of Motor Profi ciency, Second Edition (BOT-2) was used to include a measure for ball skills (Bruininks, 2005). Both motor skill test batteries have shown to be reliable and valid for primary school children (Bruininks, 2005; Deitz, Kartin, & Kopp, 2007; Kiphard & Schilling, 2007).

Moderate-to-vigorous physical activity (MVPA)

During two physical education lessons (one in the fi rst week and one in the last week of the intervention period), children in all study conditions wore accelerometers on the right hip to obtain the amount of MVPA (ActiGraph GT3x+, Pensacola, FL, USA). The accelerometer measures accelerations in three directions with a frequency of 100 Hz. Only data from the vertical axis were used. Analyses were performed in data analysis software ActiLife (v6.8.2). An epoch length of 1 s. was used (Trost, Loprinzi, Moore, & Pfeiff er, 2011). A cutoff point of >2296 counts/min was used as a measure for MVPA (Evenson, Catellier, Gill, Ondrak, & McMurray, 2008). Time in MVPA and percentage of total lesson time in MVPA were calculated.

Implementation measures

The average percentage of the total lesson time in MVPA over the two lessons was calculated as an implementation measure. The duration of the physical education lessons was obtained during the two lessons in which MVPA was measured in each study condition. The intervention teachers logged the number of intervention lessons delivered and the absence of the children during the interventions. This was used to calculate the number of intervention lessons followed by each child. The total dose of MVPA in the two intervention groups was estimated by multiplying the mean time in MVPA over the two physical education lessons with the total number of intervention lessons followed by a child. The total dose of MVPA was used to investigate the dose-response relations.

Procedure

Children in the intervention groups followed the aerobic intervention or the cognitively engaging intervention four times per week for 14 weeks during the school year (2016/2017). The interventions replaced their normal physical education lessons (two lessons per week) and two additional physical education lessons were scheduled within the school academic timetable. The lessons consisted of a warm-up phase of 10 minutes and a core phase of 20 minutes.

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130

The aerobic intervention consisted of specifically designed activities targeted at MVPA intensity. The focus was on highly repetitive and automated exercises, such as circuit training, relay games, playing tag, and individual activities like running or doing squats. The cognitively engaging intervention consisted of team games or exercises that require complex coordination of movements, strategic play, cooperation between children, anticipating the behavior of teammates or opponents, and dealing with changing task demands (Best, 2010). Children played adapted versions of games such as dodgeball, basketball, or soccer (Tomporowski et al., 2015a). Complex rules were included in the games, in a way that children were constantly challenged to think about their actions and movements. Additionally, exercises such as balancing, climbing, clambering, throwing and catching were included. The complexity of the games and exercises increased during the intervention period. Children in the control group followed their regular physical education lessons twice a week.

The interventions were provided by certificated physical education teachers recruited for this study, who received training and a manual containing a detailed description of the interventions. Cardiovascular fitness and gross motor skills were assessed at baseline and posttest, within two weeks before and after the intervention. Children were tested by trained research assistants using standardized protocols. Gross motor skills were individually assessed during one or two (depending on the class size) physical education lessons in circuit form with tests administered in a random order. The 20-m SRT was conducted during a separate physical education lesson and was administered in groups of up to 15 children.

Data analysis

Initial analyses were performed in IBM SPSS Statistics version 25.0. Outliers (z ≤ -3.29 or ≥ 3.29) were replaced with a value one unit greater than the next non-outlier value (Tabachnick & Fidell, 2007). The three study conditions were compared based on background variables (age, sex, grade, socioeconomic status [SES]), on cardiovascular fitness and gross motor skills at baseline and on implementation measures using a one-way analysis of variance (ANOVA), a χ2_{test, or an} independent sample t-test where appropriate.

A principal component analysis on the standardized scores of the gross motor skill tests was performed (baseline and posttest combined) to calculate a Bartlett factor score. The four gross motor skill components loaded highly (> 0.6) onto one factor and explained 52.0% of the total variance. This factor was used in the analysis as a measure of gross motor skills. Table 1 shows the correlation matrix and the factor loadings of the principal component analysis.

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131

Table 1. Correlation matrix and factor loadings for the principal component analysis for gross motor skills. Jumping sideways (total number of jumps) Moving sideways (total points) Backwards balancing (total steps) Upper limb coordination (total points) Factor loading 1 0.754 0.493 1 0.816 Jumping sideways Moving sideways Backwards balancing 0.337 0.410 1 0.673

Upper limb coordination 0.295 0.373 0.221 1 0.626

Table 1. Correlation matrix and factor loadings for the principal component analysis for gross motor skills

Main analyses were performed using Multilevel regression analysis (MLwiN version 2.35). Posttest cardiovascular fi tness and gross motor skills were used as dependent variables in the models. A random intercept was added to the model for each class (level 2) and each child (level 1). The fi rst model contained only covariates (sex, grade, age, SES and corresponding baseline score). Covariates that did not signifi cantly contribute to the model were excluded by means of backward stepwise deletion. Study condition was added to investigate the main eff ects of the interventions on cardiovascular fi tness and gross motor skills as compared to the control condition as well as the aerobic intervention compared to the cognitively engaging intervention. To investigate whether intervention eff ects were dependent on the corresponding baseline score, the interaction between baseline and study condition was added. To investigate the dose-response eff ect of the total dose of MVPA on the outcome variables in the intervention groups, the total dose of MVPA was added followed by the interaction between the total dose of MVPA and the study condition. To evaluate model fi t, the deviance of the model with the variable of interest was compared to the deviance of the model without the variable of interest using a χ2_{diff erence} test. A false discovery rate (FDR) correction was applied to the predicted variables in the model to account for multiple testing (q-values are shown for values after FDR correction; Benjamini & Hochberg, 1995). Level of signifi cance was set at 0.05 (one-sided) and 90% Confi dence intervals (CI) were reported.

Results

Table 2 shows the characteristics of the children in each study condition. The proportion of grade three children and age diff ered signifi cantly between the study conditions, due to the two schools that dropped-out. The three study conditions did not diff er on cardiovascular fi tness, F(2,813) = 0.11, p = 0.90, and gross motor skills, F(2,837) = 1.22, p = 0.30, at baseline (Table 3).

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132

Table 2. Descriptive statistics of the included population

Note. a_{mean ± SD;}b_n(%);c_{One-way analysis of variance;}d_{Non-parametric χ}2_test;e_{Body mass index, calculated by} weight(kg)/height(m)2_;f_{based on reference values by (Cole & Lobstein, 2012);}g_{Socioeconomic Status, calculated} by the average education level of both parents (Schaart, Mies, & Westerman, 2008); *Significantly different from the control group (p < 0.05); **Significantly different from the control group (p < 0.01); #_{Significantly different from} the aerobic intervention group (p < 0.05); ##_{Significantly different from the aerobic intervention group (p < 0.01).}

Main effects of the interventions

Table 5 shows the results of the multilevel analysis assessing the effects of the aerobic intervention and the cognitively engaging intervention on cardiovascular fitness and gross motor skills. The addition of study condition did not significantly improve the model for cardiovascular fitness, Δχ2_{(2) = 1.26, p = 0.53, and gross motor skills, Δχ}2_{(2) = 3.27, p = 0.19, indicating no effects of} aerobic physical activity and cognitively engaging physical activity as compared to the control group, and no difference between the two interventions.

Table 2. Descriptive statistics of the included population.

Aerobic intervention group Cognitively engaging intervention group Control group p-value 9.3 ± 0.7** 9.1 ± 0.6 9.2 ± 0.7 < 0.01c 48.9 47.1 50.9 0.62d 44.3* 51.2*# _54.7 _{< 0.05}d 139.4 ± 6.6 138.6 ± 7.0 138.8 ± 6.6 0.41c 33.0 ± 6.0 32.7 ± 6.8 32.1 ± 6.3 0.18c 16.9 ± 2.4 16.9 ± 2.5 16.6 ± 2.4 0.14c 30 (13.6) 32 (13.3) 47 (10.9) 0.41d 5 (2.3) 8 (3.3) 11 (2.6) Agea_(years) Sexb_{(% boys)} Gradeb_{(% 3th grade)} Heighta_(cm) Weighta_(kg) BMIa,e_(kg/m2₎ Overweightb,f_{(n (%))} Obesityb,f_(n(%)) SESa,g _{4.4 ± 0.9} _{4.7 ± 1.1}## _{4.5 ± 1.0} _0.01c

Note. a_{mean ± SD;}b_n(%);c_{One-way analysis of variance;}d_{Non-parametric χ2 test;}e_{Body mass}

index, calculated by weight(kg)/height(m)2_;f_{based on reference values by (Cole & Lobstein,}

2012); g_{Socioeconomic Status, calculated by the average education level of both parents}

(Schaart, Mies, & Westerman, 2008); *Significantly different from the control group (p < 0.05); **Significantly different from the control group (p < 0.01); #_{Significantly different from the}

aerobic intervention group (p < 0.05); ##_{Significantly different from the aerobic intervention}

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133 Table 3. Overview of baseline and posttest scores on cardiovascular fi tness and gross motor skills for the three study conditions

Note. Values are expressed as mean ± standard deviation; a_{Number of completed stages;}b_{Total number of jumps} in 15 seconds in two trials; c_{Total points in 20 seconds of two trials;}d_{Total number of steps on three wooden beams} (resp. 6 cm, 4.5 cm, and 3 cm wide), with three trials per beam and a maximum of eight steps per trial, resulting in a maximum score of 72; e_{Total score of seven activities executed with a tennis ball (maximum score is 39 points);} f_{Bartlett factor score calculated from the standardized scores of the four motor skill tests (jumping sideways,} moving sideways, backwards balancing, and upper limb coordination; baseline and posttest combined).

Implementation

Table 4 shows the mean duration of the physical education lessons, the percentage of time in MVPA, the total number of lessons followed by the children, and the total dose of MVPA. The total dose of MVPA was used for the dose-response eff ects of MVPA and was signifi cantly higher in the aerobic intervention (9.3 ± 2.5 hours) compared to the cognitively engaging intervention (7.0 ± 2.1 hours), t = 9.95, p < 0.01, 90% CI [1.93 – 2.69].

Table 3. Overview of baseline and posttest scores on cardiovascular fitness and gross motor skills for the three study conditions.

N Aerobic intervention group N Cognitively engaging intervention group N Control group Baseline 209 4.6 ± 1.8 228 4.3 ± 1.8 403 4.5 ± 1.9 Posttest 206 5.3 ± 2.2 230 5.1 ± 2.0 395 5.1 ± 2.1 Baseline 211 49.3 ± 15.2 230 48.1 ± 15.4 405 49.5 ± 15.8 Posttest 205 61.5 ± 15.6 229 55.6 ±16.0 396 57.4 ± 16.3 Baseline 211 34.1 ± 9.3 232 35.6 ± 9.2 407 33.3 ± 8.8 Posttest 206 37.5 ± 8.2 231 37.0 ± 8.9 405 37.5 ± 9.4 Baseline 212 40.1 ± 12.4 232 40.7 ± 13.6 410 40.7 ± 14.2 Posttest 206 44.6 ± 13.7 229 45.0 ± 13.3 399 44.1 ±13.6 Baseline 211 31.1 ± 5.2 223 29.9 ± 5.3 403 31.0 ± 5.2 Posttest 207 32.4 ± 4.1 230 31.2 ± 4.5 402 32.1 ± 4.3 Cardiovascular fitnessa Jumping sidewaysb Moving sidewaysc Backwards balancingd Upper limb coordinatione Gross motor skills (factorscore)f Baseline 205 -0.22 ± 1.0 218 -0.26 ± 1.0 393 -0.25 ± 0.9 Posttest 199 0.39 ± 0.9 225 0.16 ± 1.0 385 0.23 ± 1.0

Note. Values are expressed as mean ± standard deviation; a_{Number of completed stages;} b_Total

number of jumps in 15 seconds in two trials; c_{Total points in 20 seconds of two trials;}d_Total

number of steps on three wooden beams (resp. 6 cm, 4.5 cm, and 3 cm wide), with three trials per beam and a maximum of eight steps per trial, resulting in a maximum score of 72; e_Total

score of seven activities executed with a tennis ball (maximum score is 39 points); f_{Bartlett factor}

score calculated from the standardized scores of the four motor skill tests (jumping sideways, moving sideways, backwards balancing, and upper limb coordination; baseline and posttest combined).

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134 Table 4. Implementation measur es Not e. V alues ar e expr

essed as mean ± standar

d de viation; MVP A = moder at e-t o-vigor ous physic al activit y; CI = C onfidenc e Int er val; aAv er age amount of MVP of the t w o obser ved physic al educ ation lessons; bCalculat ed b y m ultiplying the av er age time in MVP A with the n

umber of lessons follo

w ed b y the child; w ay analysis of v arianc e; dIndependent samples t-t est. Table 4. Implementation measures. Control group – aerobi c interventi on group Control group - cogni tivel y engagi ng interventi on group Aerobi c interventi on group – cogni tivel y engagi ng interventi on group Aerobi c interventi on group Cogni tivel y engagi ng interventi on group Control group Mean difference (90% CI) p- value Mean difference (90% CI) p-val ue Mean difference (90% CI) p- val 34.5 ± 3.7 39.2 ± 6.5 36.9 ± 5.6 2.43 (1.73 – 3.13) <0.01 c -2.24 (-2.92 – -1.56 <0.01 c -4.67 (-5.46 – -3.89) <0.01 34.9 ± 8.4 23.5 ± 6.1 27.9 ± 8.4 -6.95 (-8.08 – -5.83) <0.01 c 4.41 (3.29 – 5.53) <0.01 c 11.36 (10.08 – 12.65) <0.01 45.6 ± 5.7 44.9 ± 7.1 0.76 (-0.22 – 1.77) 0.20 Durati on physi cal educati on lesson (mi nutes) Amount of MVPA (percentage) a Number of lessons fol lowed by the chi ld Total dose of MVPA (hours) b 9.3 ± 2.5 7.0 ± 2.1 2.31 (1.93 – 2.69) <0.01 Note. Val ues are expressed as mean ± standard devi ati on; MVPA = moderate-t o-vi gorous physi cal acti vi ty; CI = Confi dence Interval ; aAverage amount of MVPA of the two observed physi cal educati on lessons; bCal cul ated by mul tipl ying the average time in MVPA wi th the number of lessons fol lowed by the chi ld; cOne-way anal ysi s of vari ance; dIndependent sampl es t-test.

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135 Table 5. Results of the multilevel analysis for cardiovascular fi tness and gross motor skills

Note. a,b_{Respectively boys and the control group were the reference categories;}c_{signifi cance after FDR correction;} Chi-squared test between the aerobic intervention group and the cognitively engaging intervention group: cardiovascular fi tness: χ2_{(1) = 0.45, q = 0.50, gross motor skills: χ}2_{(1) = 3.25, q = 0.14; SES = socioeconomic status;} CI = Confi dence Interval.

Table 5. Results of the multilevel analysis for cardiovascular fitness and gross motor skills.

Cardiovascular fitness Gross motor skills

Fixed effects B SE qc _{90% CI} _B _SE _qc _{90% CI} Random intercept 1.35 0.22 <0.01 0.99 – 1.71 0.17 0.12 0.08 -0.03 – 0.37 Corresponding baseline score 0.85 0.03 <0.01 0.80 – 0.90 0.81 0.03 <0.01 0.76 – 0.86 Sexa _-0.30 _{0.10 <0.01 -0.46 – -0.14} SES 0.06 0.02 <0.01 0.03 – 0.09 Aerobic intervention groupb 0.10 0.28 0.36 -0.36 – 0.56 0.11 0.11 0.32 -0.07 – 0.29 Cognitively engaging 0.32 0.28 0.16 -0.14 – 0.78 -0.11 0.11 0.16 -0.29 – 0.07 0.49 0.12 <0.01 0.06 0.02 <0.01 intervention groupb Random effects Variance classes Variance students 1.45 0.08 <0.01 0.32 0.02 <0.01 Deviance 2589.42 1218.46 Deviance covariates model 2590.68 1221.73

Note. a,b_{Respectively boys and the control group were the reference categories;}c_{significance after}

FDR correction; Chi-squared test between the aerobic intervention group and the cognitively engaging intervention group: cardiovascular fitness: χ2_{(1) = 0.45, q = 0.50, gross motor skills: χ}2₍₁₎

= 3.25, q = 0.14; SES = socioeconomic status; CI = Confidence Interval.

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136

Eff ects of baseline levels

The addition of the interaction between study condition and baseline cardiovascular fi tness did signifi cantly improve the model for cardiovascular fi tness, Δχ2_{(2) = 7.45, p = 0.02. As shown} in Figure 2A, children with lower cardiovascular fi tness at baseline benefi ted more from the cognitively engaging intervention than from the aerobic intervention, meanwhile children with higher cardiovascular fi tness at baseline benefi ted more from the aerobic intervention than from the cognitively engaging intervention, t = 2.61, q = 0.02, 90% CI [- 0.29 – -0.07], and the control condition, t = 2.24, q = 0.03, 90% CI [0.04 – 0.24].

The addition of the interaction between study condition and baseline gross motor skill performance did not signifi cantly improve the model for gross motor skills, Δχ2_{(2) = 2.19, p = 0.33,} indicating that eff ects of the interventions for gross motor skills did not depend on baseline score.

Figure 2. The eff ect of baseline level on cardiovascular fi tness (A). Cardiovascular fi tness is shown adjusted for sex, baseline score, and condition. Figure 2B and 2C show the eff ects of the total dose of moderate-to-vigorous physical activity (MVPA) on cardiovascular fi tness (B) and gross motor skills (C). Cardiovascular fi tness is shown adjusted for sex, baseline score, condition, and total dose of MVPA. Gross motor skills score is shown adjusted for socioeconomic status, baseline score, condition, total dose of MVPA, and the interaction between study condition (aerobic vs cognitively engaging physical activity) and the total dose of MVPA.

0 1 2 3 4 5 6 7 8 9 10 0 1 2 8 9 10

Cardiovascular fitness posttest (stages)

3 4 5 6 7

Cardiovascular fitness baseline (stages) Aerobic intervention Cognitively engaging intervention Cardiovascular fitness posttest (stages) Gross motor skills posttest (factor score) 0 2 4 6 8 10 12 0 5 10 15

Total dose MVPA (hours)

20 -3 -2 -1 0 1 2 3 0 5 10 15

Total dose MVPA (hours) 20

A B C 0 1 2 3 4 5 6 7 8 9 10 0 1 2 8 9 10

Cardiovascular fitness posttest (stages)

3 4 5 6 7

Cardiovascular fitness baseline (stages) (stages) Aerobic intervention Cognitively engaging intervention Cardiovascular fitness posttest (stages) Gross motor skills posttest (factor score) 0 2 4 6 8 110 12 0 5 10 15

Total dose MVPA (hours)

20 -33 -22 -11 0 1 2 3 0 5 10 15

Total dose MVPA (hours) 20

A B C Control group Aerobic intervention Cognitively engaging intervention

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Dose-response eff ects of MVPA

The total dose of MVPA did signifi cantly contribute to the model for cardiovascular fi tness, Δχ2₍₁₎ = 9.29, p < 0.01 (Figure 2B). A higher dose of MVPA during the interventions was related to higher cardiovascular fi tness at the posttest, t = 3.08, q = <0.01, 90% CI [0.05 – 0.17]. The interaction between the total dose of MVPA and condition did not signifi cantly improve the model, Δχ2_{(1) =} 0.91, p = 0.34, indicating that the eff ects of the total dose of MVPA on cardiovascular fi tness did not diff er between the aerobic intervention and the cognitively engaging intervention.

Total dose of MVPA did not signifi cantly contribute to the model for gross motor skills, Δχ2_{(1) =} 0.04, p = 0.84, but the addition of the interaction between total dose of MVPA and study condition signifi cantly improved the model, Δχ2_{(1) = 4.79, p = 0.03 (Figure 2C). There was a positive eff ect of} the total dose of MVPA on gross motor skills in the cognitively engaging intervention, but not in the aerobic intervention, t = 2.15, q = 0.03, 95% CI [0.02 – 0.13].

Discussion

This study showed no main eff ects of the aerobic intervention and the cognitively engaging intervention on cardiovascular fi tness and gross motor skills in primary school children. However, the investigation of the eff ect of baseline scores showed that children with lower baseline cardiovascular fi tness benefi ted more from the cognitively engaging intervention than from the aerobic intervention, while children with higher baseline cardiovascular fi tness benefi ted more from the aerobic intervention than from the cognitively engaging intervention and the control condition. Furthermore, a higher dose of MVPA was related to better cardiovascular fi tness after both interventions and to better gross motor skills after the cognitively engaging intervention. Children in the intervention groups followed - on average - 3.2 physical education lessons per week. While this is less than the prescribed frequency of four times per week, it proved possible to increase the number of physical education lessons in primary schools. In addition, it was shown that the level of MVPA during physical education can be increased: children in the aerobic intervention exercised on average 35% of the time in MVPA, which was signifi cantly more than children in the control condition (28%) and the cognitively engaging intervention (24%). These fi ndings show that the dose of MVPA that children receive at school can be increased by changing the content and frequency of physical education lessons, which confi rms the fi ndings in the meta-analysis by Lonsdale et al. (2013).

Both interventions showed no main eff ect on cardiovascular fi tness. This is contradictory to our hypothesis and to previous studies showing that cardiovascular fi tness can be enhanced by physical activity interventions (Sun et al., 2013). The lack of signifi cant eff ects at a group level may be explained by the fact that the frequency of physical education lessons was less than prescribed and therefore too low to fi nd eff ects on cardiovascular fi tness (Sun et al., 2013). In addition, although children within the intervention groups received equal instructions, the variation in MVPA between children was high. The average dose of MVPA might therefore have been too low to fi nd eff ects at a group level. However, it was shown that more time in MVPA was related

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to higher cardiovascular fitness after the interventions, which confirmed our hypothesis and is consistent with previous studies showing that the higher the amount of physical activity, the greater the benefits on cardiovascular fitness (Janssen & LeBlanc, 2010; Parikh & Stratton, 2011). A significant effect of baseline cardiovascular fitness was found, showing that children with lower baseline cardiovascular fitness benefited more from the cognitively engaging intervention than from the aerobic intervention. Possibly, the intensity of the aerobic intervention was too challenging for children with lower baseline cardiovascular fitness. This might have led to lower involvement in, and less improvement from, the aerobic intervention compared to higher involvement in, and more improvement from, the cognitively engaging intervention for children with lower baseline cardiovascular fitness (Fairclough & Stratton, 2004). Furthermore, it was found that children with higher baseline cardiovascular fitness benefited more from the aerobic intervention than from the cognitively engaging intervention or control condition. Likely, children with higher cardiovascular fitness levels at the baseline need a higher dose of MVPA to increase cardiovascular fitness (Borresen & Lambert, 2009). As the dose of MVPA was higher in the aerobic intervention than in the cognitively engaging intervention, the potential for higher fit children to increase their cardiovascular fitness was greater in the aerobic intervention than in the cognitively engaging intervention or in the control condition. These findings imply that it is important to take into account baseline levels of cardiovascular fitness in the development and implementation of interventions (Kristensen et al., 2010).

There were no significant effects of the interventions on gross motor skills. This is in contrast to our hypothesis and to the findings in the meta-analysis by Morgan et al. (2013) showing that school-based interventions significantly improved gross motor skills in youth when developmentally appropriate motor skill learning experiences are delivered by physical education teachers (Ashy, Lee, & Landin, 1988; Gallahue & Donnelly, 2007). Possibly, the interventions in the current study included less opportunities for children to learn gross motor skills than in studies that designed motor skill learning interventions. However, there was a positive relation between MVPA and gross motor skills in the cognitively engaging intervention. This may indicate that children that are more involved in the games and exercises in the cognitively engaging intervention have more opportunities to practice gross motor skills, which in turn, results in better gross motor skills (Willingham, 1998).

Strengths, limitations and directions for future research

Strengths of this study were the development of two interventions, the large sample size and the recruitment of physical education teachers that delivered the interventions to minimize the load for classroom teachers. A limitation of this study was the absence of an indication for the amount of practicing or applying gross motor skills so dose-response effects between practicing gross motor skills and motor skill performance could not be considered. This is important for future research, because the amount of repeated practice and interactions with the environment is important in the development of gross motor skills (Willingham, 1998). Secondly, MVPA was only measured in two of the physical education lessons. Therefore – although we measured the two

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139 most representative lessons - the dose of MVPA in the intervention groups was only an estimation of the time that children were engaged in MVPA. Additionally, we did not measure children’s daily physical activity levels. Therefore, we could not investigate whether the interventions led to an increase or decrease in daily physical activity. For future studies, it is recommended to investigate the contribution of interventions to children’s daily physical activity levels.

Practical implications

The results of this study have practical implications that need to be addressed. First, the results imply that the time in MVPA during physical education lessons can be increased by implementing games and activities with the main aim to increase MVPA. Second, it was shown that cardiovascular fi tness can be improved, but the eff ects are highly dependent on baseline cardiovascular fi tness. This highlights the importance of taking into account baseline cardiovascular fi tness of children while developing or delivering physical activity interventions. Finally, individual exposure to physical activity is an important factor that infl uences the eff ectiveness of an intervention. Therefore, it is important to challenge all children to engage highly in MVPA during physical activity interventions.

Conclusions

In conclusion, no main eff ects of the aerobic intervention and the cognitively engaging intervention on cardiovascular fi tness and gross motor skills were found. However, this study showed that the eff ects of aerobic physical activity and cognitively engaging physical activity in physical education on cardiovascular fi tness are related to baseline levels. In addition, children with a higher dose of MVPA demonstrated higher cardiovascular fi tness after both interventions and enhanced gross motor skills after the cognitively engaging intervention. The results of this study highlight the importance of taking into account that baseline levels of cardiovascular fi tness and individual exposure to physical activity are important factors that infl uence the eff ectiveness

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