The BOOSTH study is a cluster randomized controlled trial at 16 primary schools located in the province of Limburg (the Netherlands). Schools will be randomized to standard physical education curriculum plus BOOSTH (intervention schools) or standard physical education curriculum only (control schools). Stratified randomization will be applied by an independent researcher. Stratification variables are community (ie, schools need to be located within the same community) and school size (ie, number of children in a school). Control schools will only be visited for physical measurements. The inclusion criteria for the children are as follows: boys and girls in classes five to seven (age range 7-12 years) at the moment of inclusion and written informed consent from both parents and children older than 12 years. Children will be excluded if they are wheelchair dependent.
The sample size calculation is based on the primary outcome as follows: to detect a difference in MVPA between the intervention and control groups after 12 months. Children are nested within schools, with eight intervention and eight control schools.
Children from grades five till seven (age range 7-12 years) will be included in this study. Based on the participation rates of other Dutch school-based PA interventions, it is expected that about 60 children per school will participate. Therefore, 480 children per condition (intervention/control) (8×60=480) will be included. It is assumed that the intraclass correlation coefficient is between 0.05 and 0.10 [
With the given sample size and assuming a significance level (α) of .05 and a power of 80%, we can demonstrate a Cohen
The BOOSTH intervention consists of an online arcade game that can be synchronized with a BOOSTH activity tracker using the BOOSTH mobile app. In addition, the app includes “BOOSTH battle” to enable competition between groups.
After baseline measurements, children at the intervention schools will receive the BOOSTH activity tracker for free. The activity tracker, accompanied with a user manual and an oral instruction on how to use BOOSTH, will be provided to all children and parents during a regular school day. To install the BOOSTH app, a mobile device with Bluetooth and internet access is needed. Parents are asked to download the app together with their child. The children will receive an instruction to wear the BOOSTH activity tracker around their wrist during waking hours, except during water activities (eg, showering and swimming). One week after BOOSTH delivery, the research team will visit participating schools. Children, their parents, and their teachers will have the opportunity to ask questions about possible issues they encounter during the first week. No further instructions, activities, or support are part of the intervention.
The BOOSTH intervention includes several behavioral change techniques with the intention to stimulate PA and positively change the attitude toward PA. Using the BOOSTH activity tracker, the child can track step count. The use of activity trackers could help children set achievable goals and monitor their progress toward the goals [
As shown in
Overview of the BOOSTH study and measurements. The questionnaires for children included subjective PA behavior, screen time, health-related quality of life, and motivation toward PA. PA: physical activity.
The primary outcome is MVPA (min/day), which will be measured with Actigraph GT3X (ProCare). This is a triaxial accelerometer, and it has been validated for the measurement of PA behavior in children. The children will be asked to wear the accelerometer attached via a waistband on the right hip for 7 consecutive days during waking hours, except during water activities (eg, showering and swimming) and contact sports (eg, judo). Accelerometry data will be downloaded with 10-s epochs using the Actilife software (Actigraph). Valid wear time will be defined as a minimum of 4 days, with at least 480 minutes per day of recording, including 1 weekend day. Derived data are expressed as mean counts per minute (cpm). To establish time spent in different intensity categories (sedentary behavior, light PA, and MVPA), the cutoff points developed by Everson et al will be used [
In addition, the self-administered validated Baecke questionnaire (for children) will be used to assess the amount of habitual PA ranging from 1 (lowest activity) to 5 (highest activity) [
Height, weight, and waist circumference will be measured in duplicate, and the average of both measurements will be reported. Body weight will be measured using an electric scale (Seca 877, Seca) to the nearest 0.1 kg. Heavy clothing and shoes will be removed before the measurement. Standing height will be measured using a portable stadiometer (Seca 213 stadiometer, Seca), and children will be asked to stand straight and look forward. Subsequently, BMI (weight [kg]/height [m]2) will be calculated and age- and sex-specific BMI z-scores will be calculated (TNO Growth Calculator, TNO) [
Systolic and diastolic blood pressure will be measured using an automated sphygmomanometer (Mobil-O-Graph, Revision 4.6 08/2011, IEM GmbH). Blood pressure will be measured on the nondominant arm in the sitting position. Measurements will be performed thrice, with 1 minute of rest in between measurements. The reading will be recorded to the nearest 1 mmHg. A mean value will be calculated out of these three readings. The mean systolic and diastolic blood pressure values will be computed into z-scores using the LMS method (L, curve Box-Cox; M, curve median; S, curve coefficient of variation) and reference values as described by Wühl et al [
Retinal microvasculature will be measured with fundus photography, which is a noninvasive tool to measure cardiovascular risk factors. The retinal characteristics that have received the most attention so far in predicting cardiovascular disease are the central retinal arteriolar equivalent (CRAE) and the central retinal venular equivalent (CRVE). Photographs of the retinal microvasculature will be taken using a fundus camera (Topcon TRCNW-300, Topcon Corporation). Subjects will be seated with their head resting on a chinrest, thereby looking straight in the camera. The fundus camera automatically focuses on the subject’s pupils and will take a photo of the retina of the right eye. A fundus photo with a centralized optic disc will be obtained for each subject. Fundus photos will be analyzed using RetinaCheck, and manual modification will be done using the retinal health information and notification system (RHINO). These programs are developed in collaboration with the Department of Biomedical Engineering at Eindhoven University of Technology in the Netherlands, using a series of innovative brain-inspired algorithms as described by ter Haar Romeny et al [
The maximum aerobic performance of the children will be assessed with a maximum multistage 20-m shuttle run test. Children run back and forth on a 20-m course and have to touch the 20-m line before or at an audio signal that is emitted from a prerecorded tape. The frequency of the audio signal is increased by 0.5 km/h each minute from a starting speed of 8.5 km/h. The test ends when the child has to stop owing to fatigue or when the child fails to reach the 20-m line concurrent with the audio signal on two consecutive occasions. The children will be constantly encouraged to run for as long as possible throughout the course of the test. The last completed oxygen uptake (VO2max) (Y, mL/kg/min) will be calculated from the speed (X, km/h) corresponding to that stage (speed=8+0.5 stage number) and age (A, year) as follows: Y=31.025+3.238X−3.248A+0.1536AX [
Self-reported screen time will be reported separately for weekdays and weekend days using the following questions: “How many hours a day during the last 4 weeks did you watch TV on a normal weekday/weekend day?” and “How many hours a day during the last 4 weeks did you play console games or use a computer for your free time activities on a normal weekday/weekend day?” Possible responses are “not at all,” “0.5 hours per day,” “one hour per day,” “2 hours per day,” “2.5 hours per day,” “3 hours per day,” “3.5 hours per day,” and “4 hours or more per day.” Total screen time will be reported as minutes spent on watching television plus computer use. At 3, 6, and 12 months, a question about changes in screen time since the introduction of BOOSTH will be included in the questionnaire.
HRQOL will be assessed using the validated Kidscreen and validated Pediatric Quality of Life Inventory (PedsQL) questionnaires. The 23-item PedsQL addresses the multidimensional scales of physical, emotional, social, and school functioning. The questionnaire consists of five options ranging from “never” to “almost always” [
Motivation toward PA will be measured using the self-administered validated Behavioral Regulation in Exercise Questionnaire-2 (BREQ2). The BREQ2 consists of 19 questions with a 5-point scale, which measures different aspects of motivation (external regulation, identification, introjection, integration, motivation, and intrinsic regulation) and has been shown to have good factorial validity [
Parents will be asked to fill in an online questionnaire regarding family composition, country of birth, educational level, and self-reported height/weight. In addition, parents will be asked to fill in the validated 85-item comprehensive general parenting questionnaire (CGPQ). The CGPQ assesses the following five key parenting constructs that have been identified across multiple theoretical approaches of parenting: “nurturance,” “structure,” “behavioral control,” “coercive control,” and “overprotection” on a five-factor scale [
The parent version of the validated Kidsscreen-27 questionnaire will be used to determine a HRQOL score of the child, and it consists of 27 questions. These questions are similar to the Kidsscreen-27 child version [
To understand which components of the intervention are successful, feasibility of the BOOSTH intervention will be assessed using a mixed-methods design including semistructured focus groups with teachers and evaluation questionnaires. In addition, the strengths, limitations, opportunities, and recommendations for future development will be asked.
Semistructured focus group interviews will be performed with teachers from the intervention schools. Prefixed interview guides will be used, with the possibility of additional follow-up questions, which allows the researcher to cover both contextual factors and intervention implementation. Questions will be asked about the introduction lesson of BOOSTH, the implementation and stimulation of BOOSTH by the teachers, and suggestions for future development of BOOSTH.
Children and their parents will be asked to fill in an evaluation questionnaire about their experiences with BOOSTH. Teachers will be asked to fill in an evaluation questionnaire about the implementation of the BOOSTH intervention.
Children who are allocated to the intervention schools will receive the BOOSTH activity tracker. The BOOSTH activity monitor is a lightweight triaxial accelerometer–based activity monitor, which is worn around the wrist and measures the step count. Moreover, the BOOSTH activity monitor resets automatically at midnight and stores data of the previous day automatically on the device. Data are stored on the device for 30 days. A child or parent has to synchronize the BOOSTH activity monitor with a smartphone or tablet to retrieve the measured step count. The BOOSTH activity tracker will be used as a motivation tool to promote PA. The step count on the BOOSTH activity tracker will not be used for research purposes.
Numerical variables will be presented as mean and SD or median and IQR where appropriate. Categorical data will be presented as number and percentage of participants in each of the possible categories. Baseline characteristics will be analyzed for differences between the groups, using independent sample
The feasibility of the study will be investigated using a mixed-methods design. Qualitative data of the focus group interviews will be audio recorded and transcribed verbatim. Interview transcripts will be coded by themes and concepts using NVivo version 12 software (QSR International). Coding will be performed by two researchers.