Active Smarter Kids (ASK): Rationale and design of a cluster-randomized controlled trial investigating the effects of daily physical activity on children’s academic performance and risk factors for non-communicable diseases

Sixty schools, encompassing 1202 fifth-grade children, fulfilled the inclusion criteria, and agreed to participate. This represented 86.2 % of the population of 10-year-olds in the county, and 95.2 % of total possible recruitment. We randomized 30 schools for the intervention (I-schools) and 30 schools for the control (C-schools) arm. A neutral third party (Centre for Clinical Research, Haukeland University Hospital, Norway) performed the randomization. After randomization, three schools (two I-schools and one C-school) from the same municipality declined to participate. In total, 1145 (97.4 %) of 1175 children from 57 schools (28 I-schools and 29 C-schools) agreed to participate in the study.

The ASK study is embedded in a socio-ecological conceptual framework that focuses on positive physical activity behaviors [9]. In brief, the socio-ecological model acknowledges the role of proximal (e.g. individual and social) and more distal (e.g. school physical environment, school policy) determinants of health behavior change as necessary to achieve sustained positive health behaviors. To address individual and social determinants we adopted specific theoretical frameworks including Harter’s Competence Motivation Theory [10], Achievement goal theory [11] and Ryan & Deci’s self-determination theory [12]. In line with these theories the ASK intervention emphasizes creating autonomy supporting and mastery oriented teacher-student interaction in order to enhance students’ physical activity behavior by positively influencing their perception of competence, self-efficacy, and intrinsic motivation for physical activity.

All participating children were tested at baseline and post intervention. The exception was physical activity which was assessed at baseline, at the midpoint of the intervention period and at post intervention. We describe each variable assessed in the following sections.

Academic performance in 1) reading, 2) numeracy, and 3) English was measured using specific standardized Norwegian National tests designed and administrated by The Norwegian Directorate for Education and Training (NDET) [13]. The three different tests were administered on three different days, both at the baseline and post intervention test. Tests are extensively verified for validity and reliability by NDET and are aligned with competencies demanded from all schools by the national curriculum. For ASK, we analyzed reading, numeracy and English individually and as a composite score.

We assessed the three core executive functions identified by Miyake et al. (2000) [14], i.e. inhibition, cognitive flexibility and working memory using four pen and paper tests. The tests were administered in a quiet room at the children’s school. All tests required 15–20 min to complete. 1) To assess inhibition we used Golden’s version of the Stroop test [15, 16]. 2) To assess cognitive flexibility we used two tests, one verbal (Verbal fluency) and one nonverbal test (The Trail Making Test) [17]. 3) To assess working memory we used a digit span test with digits both forward and backward (Wechsler Intelligence Scale for Children, 4th ed; WISC-IV) [16].

Physical activity was measured by triaxial accelerometry (ActiGraph GT3X+, LLC, Pensacola, Florida, USA). ActiGraph accelerometry uses the most widely applied instrument for objective assessment of physical activity and has been extensively tested for validity and reliability in children [18]. Children were instructed to wear the accelerometer on the right hip over seven consecutive days at all times, except during water activities or while sleeping. A wear-time of ≥ 480 min/day was applied as a criterion for a valid day. Periods of ≥ 20 min of zero counts are defined as non-wear time [19]. The number of ‘valid days’ vary depending on the analyses performed. Outcomes for physical activity levels are total physical activity level (counts/min), sedentary behavior (min/day and percentage of valid wear time), light physical activity, moderate physical activity, moderate to vigorous physical activity and vigorous physical activity (min/day), using previously applied and established cut points [20, 21]. All analyses were based on accumulation of data over 10 s epochs.

Cardiorespiratory fitness was measured with an intermittent practicable running field test (the Andersen-test [22]) that has demonstrated reliability and validity for our target age group [23]. The Andersen-test was administered as per standard procedures. The children were tested indoors on a wooden or rubber floor in groups of 10–20 children. The test required 10 min to perform. Children ran from one end line to another (20 m apart) in an intermittent to-and-fro movement, with 15-s work periods and 15-s breaks (standing still). We recorded the distance covered as the outcome for analysis.

Muscle strength (i.e., endurance, isometric and explosive strength) was measured using reliable and validated selected tests from the Eurofit test battery [24]: 1) Upper limb strength – handgrip strength using a hand dynamometer (Baseline® Hydraulic Hand Dynamometer, Elmsford, NY, USA); 2) Explosive strength in the lower body, standing broad jump. Muscle strength tests were recorded both individually and as a composite score for analyses.

Motor skills were measured using a battery of three tests: 1) Catching with one hand and throwing at a wall target constitute the aiming and catching subgroup of the movement-ABC-2; 2) Throwing at a wall target; 3) Ten times 5 m sprint. Tests 1) and 2) are from the Movement Assessment Battery for Children 2 (Movement ABC-2), age band 3 (11–16 years) [25], and test 3) is from Eurofit test battery [24]. Reliability and validity of these tests are well documented [26‐29]. The Movement ABC-2 demonstrated good concurrent and convergent validity [30, 31]. We recorded motor skills tests both individually and as a composite score for analyses.

Body mass (weight; 0.1 kg) was measured using an electronic scale (Seca 899, SECA GmbH, Hamburg, Germany) with children wearing light clothing. Stature (height; 0.1 cm) was measured with a portable Seca 217 (SECA GmbH, Hamburg, Germany). The child was asked to face forward, with shoes removed. We calculated body mass index (kg · m⁻²) as weight (kg) divided by the height squared (m²).

Waist circumference was measured with a Seca 201 (SECA GmbH, Hamburg, Germany) ergonomic circumference measuring tape. The measure was taken two cm over the level of the umbilicus (0.5 cm) with the child’s abdomen relaxed at the end of a gentle expiration. The child stood with arms hanging slightly away from the body. We collected two measurements from each child. If the difference between measures was a greater than one cm, we obtained a third measurement; the mean of two closest measurements are used for analyses.

Body fat was measured using four skinfold thickness sites (biceps, triceps, subscapular, and suprailiac) on the left side of the body using a Harpenden skinfold caliper (Bull; British Indicators Ltd., West Sussex, England) as per the criteria described by Lohmann et al. [32]. The Harpenden skinfold caliper has been tested for validity and reliability in children [33]. All measurements were conducted in a private room. The caliper was placed around the skinfold one cm below and to the left where the skin was held between thumb and forefinger. We collected two measurements at each site (in sequence). If the difference between measures was a greater than two mm, we obtained a third measurement; the mean of the two closest measurements are used for analyses. The skinfold calipers was calibrated each time they were moved between measurement sites.

Children self-assessed their pubertal stage as per the Tanner method [34] using a scale of color images proposed by Carel and Leger [35]. Children were given standardized series of images with explanatory text. We used a scale based on pictures of pubic hair for both sexes and of breast and genital development for girls and boys, respectively. We created a relaxed atmosphere for this assessment and the researcher was of the same sex as the child. In a private room, children were asked to read the brief descriptions for each stage, and instructed to put a checkmark in the box below the picture that best represented their stage of development for each component.

Systolic and diastolic blood pressure (BP) was measured using the Omron HBP-1300 automated BP monitor (Omron Healthcare, Inc, Vernon Hills, IL, US). The device is validated as per the AAMI protocol using the ANSI/AAMI/ISO standard (Omron, 2015) [36]. Children rested quietly for ten minutes in a sitting position with no distractions before BP was measured. During measurement, each child sat in a quiet room; BP was measured on the upper right arm using an appropriate sized cuff. We took four measurements, with a one-minute interval. We used the mean of the last three measurements for analyses. If a difference > five mmHg between measurements was found, we obtained one extra measurement, in which case the mean of the last four are used.

After an overnight fast, between 08:00 a.m. and 10:00 a.m., a nurse or phlebotomist collected an intravenous blood sample from each child’s antecubital vein. Serum was obtained according to a standardized protocol consisting of the following steps: 1) Blood plasma was collected in 5 ml tubes with gel (Vakuette® Serum Gel with activator, G456073). 2) Tubes were carefully turned upside-down five times and placed vertically for coagulation. 3) After 30 minutes the sample was centrifuged at 2000 G for 10 minutes. Serum was then visually inspected for residues and centrifugation was repeated if residue was present. 4) The serum tube was kept in refrigerator at 4 °C before pipetting 0,5 ml into cryo tubes. 5) The cryo tubes were then stored at -80 °C prior to biochemistry analyses. 

Serum samples were analyzed for constituents related to traditional risk factors for NCDs, such as insulin, glucose and the standard lipid panel (triglycerides, total cholesterol, high density lipoprotein cholesterol (HDL) and low density lipoprotein cholesterol (LDL)) using standard laboratory methods. Baseline and post intervention samples were analyzed at the same time in one batch at an ISO certificated laboratory.

Analyses of low molecular weight metabolites and lipoprotein distribution was performed for serum samples using proton nuclear magnetic resonance (1H-NMR) spectroscopy. The proton NMR profiles of low molecular metabolites (fatty acids and amino acids) were obtained by using a standard experimental set-up [37]. For lipoproteins we made a minor modification to the experimental protocol used by Mihaleva et. a.l (2014) [38]. Lipoprotein features such as subclass concentrations for HDL, LDL etc. and average particle size of each main class were derived from the NMR profiles. Fatty acid analysis was performed according to the following protocol: 200 µL serum sample is weighed into 10 mL glass tubes and water evaporated under nitrogen, followed by adding 150 µL internal standard (triheptadecanoin, 0.4855 mg/mL). After evaporating the solvent the samples are derivatized to fatty acid methyl esters (FAME) by direct esterification in methanolic HCl at 90 °C for 2 h under nitrogen atmosphere [39]. FAMEs will be extracted and analyzed by gas chromatography as described in Gudbrandsen et al. [40]. The samples are run in a randomized sequence and the FAME reference mixture GLC-461 (Nu-Chek Prep, Elysian, MN, USA) will be analyzed as every 10th sample. Chromatographic areas are corrected by empirical response factors calculated from the GLC-461 mixture. The amounts of FAs are thereafter quantified by means of the internal standard. The total amounts of FAs in each serum sample are converted to amounts in μg per g sample by dividing with the sample weights. 

We investigated the embodied experiences and interpersonal relationships of teaching and learning in physical activity from the perspectives of children, teachers and parents/guardians using qualitative methodologies. The purpose was to obtain an in-depth understanding of pedagogical processes taking place in the ASK study. More specifically, we identified purposive sample of classes from two I-schools and two C-schools. The sample criteria emphasized variation in school location, school and class size, teachers’ education and experience with PE and physical activity, and the schools’ overall focus on physical activity. In total 100 children with parents’/guardians’ approval and seven teachers provided informed written consent to participate. All children participated in a drawing and writing task and one group interview. The students were also observed by the researcher during one PE lesson. This data, together with teachers’ description of their students in PE lessons, were used to choose children to further in-depth studies.

We conducted in-depth interviews and field observations including short video recordings with 32 children. Teachers were interviewed (individually and in groups) and observed; we also interviewed two groups of parents. We deem insight attained using multiple methods and perspectives to be essential in research with children, as adult researchers may have difficulty interpreting a child’s perspective [52, 53]. Further, a deeper understanding of childrens’, teachers’, and parents’/guardians’ perspectives enriched and gave a nuanced picture of processes leading to certain outcomes from the main trail. Data (i.e., transcripts of interviews, field notes, drawings and writings, pictures and video recordings) were structured and explored using the software program Nvivo 10 (QSR International Pty Ltd 2015). Developing in-depth knowledge is an iterative process where preliminary interpretations of the empirical material are brought together with discussions on theoretical significance in increasing detail.

We consider empirical data as a construct created in a specific cultural and historical context, influenced by the interplay between the researcher and the participant, and the researcher’s theoretical underpinning. Empirical data are used as “a critical dialogue partner” and as an inspiration to challenge and rethink established taken-for-granted assumptions and theories [54]. Thus our approach differed from a more conventional approach where empirical data are seen as separate from theory, but are used to guide and validate theory development. By these means we aim to interpret the children’s embodied experiences and pedagogical practices during the ASK intervention as an interactive whole where researchers’ pre-understanding, alternative theoretical input, and empirical data constitute the dialogue setting [54].

We further created a reflexive account on children’s embodied experiences and pedagogical practices during the ASK intervention. Thus, the qualitative approach thus shed light on «what’s going on» in schools during the intervention period: How do children interact with each other and the teachers within the schools during the intervention, and, in particular, how is it to be a child in an I-school? In addition, this gives us a basis to discuss the teaching and learning processes, the possible benefits and pitfalls in the intervention, as well as to evaluate whether the intervention and the ASK study as a whole might serve as tools towards creating an improved atmosphere for learning in the schools in the future.

Regarding adherence to the intervention program, school administrators at the 57 schools recorded every child’s absence from school. Administrators also recorded children’s injuries and the names of children who did not participate in physical activity lessons.

We assessed the extent to which the intervention was implemented (dose), the quality of the implementation (fidelity), as well as feasibility as perceived by teachers and others.

ASK teachers at the 28 I-schools completed a report each week that described activities performed throughout the school day, the intensity of the activities (on a 1 to 3 scale) and the number of minutes allocated to physical activity/PE in each ASK session. All 29 C-schools, at the end of the school year, completed a report that describes the activities that were performed and the estimated time allocated to physical activity/PE during the school year (minutes/week).

Implementation research suggests that to successfully implement a large scale study within the school system, researchers must engage partners early and stakeholders should be active participants in design, implementation and dissemination of the ‘innovation’ [63]. Importantly, school-based models will be more likely to be sustained if they are anchored and supported by policy within the school system [64]. We carried out a four-stage plan to achieve this.

First, the study was accepted by “The forum for development in kindergartens and schools in Sogn and Fjordane County”. This educational forum was established in 1997 in Sogn and Fjordane County as an arena to discuss, translate and integrate educational policies regarding school quality and school development. The forum includes professional executives of the most important educational authorities and organizations in the Sogn and Fjordane, and it is highly respected by school administrators and teachers in the county. Second, through the “The forum for development in kindergartens and schools in Sogn and Fjordane County” we obtained access to a series of already established meeting venues for all county school leaders and principals, who accepted the study at the operations level. Third, parents/guardians were invited to meet with us at individual schools, where we provided a description of the study (oral and written), including our aims and any possible hazards, discomfort, or inconvenience. We also clearly described the measurement protocol and procedures and addressed any questions. We emphasized that children were free to withdraw from the study or from any measurements at any time, without providing an explanation. Fourth, we carried out an extensive anchoring process with the ASK teachers in the I-schools.

Procedures and methods used in the ASK study conform to the ethical guidelines defined by the World Medical Association’s Declaration of Helsinki and its subsequent revisions [65]. The study protocol was approved by The Regional Committee for Medical Research Ethics. The ASK study adopted a population-based approach that focuses on- and treats all children equally and considerately. We obtained written consent from each child’s parent/guardian prior to all testing. Reporting are anonymous and it is not be possible to identify individual participants in any published materials.