Open Access Study protocol

Study protocol of physical activity and sedentary behaviour measurement among schoolchildren by accelerometry - Cross-sectional survey as part of the ENERGY-project

Mine Yıldırım1, Maïté Verloigne2, Ilse de Bourdeaudhuij2, Odysseas Androutsos3, Yannis Manios3, Regina Felső4, Éva Kovács4, Alain Doessegger5, Bettina Bringolf-Isler6, Saskia J te Velde7, Johannes Brug7 and Mai JM Chinapaw1*

Author Affiliations

1 Department of Public and Occupational Health and the EMGO Institute for Health & Care Research, VU University Medical Center, Amsterdam, the Netherlands

2 Department of Movement and Sport Sciences, Ghent University, Ghent, Belgium

3 Department of Nutrition and Dietetics, Harokopio University, Athens, Greece

4 Department of Paediatrics, University of Pécs, Pécs, Hungary

5 The Federal Institute of Sport, Magglingen, Switzerland

6 Department of Epidemiology and Public Health, Swiss TPH and University of Basel, Switzerland

7 Department of Epidemiology and Biostatistics and the EMGO Institute for Health & Care Research, VU University Medical Center, Amsterdam, the Netherlands

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BMC Public Health 2011, 11:182  doi:10.1186/1471-2458-11-182

Published: 25 March 2011

Abstract

Background

Physical activity and sedentary behaviour among children should be measured accurately in order to investigate their relationship with health. Accelerometry provides objective and accurate measurement of body movement, which can be converted to meaningful behavioural outcomes. The aim of this study was to evaluate the best evidence for the decisions on data collection and data processing with accelerometers among children resulting in a standardized protocol for use in the participating countries.

Methods/Design

This cross-sectional accelerometer study was conducted as part of the European ENERGY-project that aimed to produce an obesity prevention intervention among schoolchildren. Five countries, namely Belgium, Greece, Hungary, Switzerland and the Netherlands participated in the accelerometer study. We used three different Actigraph models-Actitrainers (triaxial), GT3Xs and GT1Ms. Children wore the device for six consecutive days including two weekend days. We selected an epoch length of 15 seconds. Accelerometers were placed at children's waist at the right side of the body in an elastic belt.

In total, 1082 children participated in the study (mean age = 11.7 ± 0.75 y, 51% girls). Non-wearing time was calculated as periods of more than 20 minutes of consecutive zero counts. The minimum daily wearing time was set to 10 hours for weekdays and 8 hours for weekend days. The inclusion criterion for further analysis was having at least three valid weekdays and one valid weekend day. We selected a cut-point (count per minute (cpm)) of <100 cpm for sedentary behaviour, <3000 cpm for light, <5200 cpm for moderate, and >5200 cpm for vigorous physical activity. We also created time filters for school-time during data cleaning in order to explore school-time physical activity and sedentary behaviour patterns in particular.

Discussion

This paper describes the decisions for data collection and processing. Use of standardized protocols would ease future use of accelerometry and the comparability of results between studies.