Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Hirschengraben 84, 8001, Zurich, Switzerland
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Accelerometer-derived physical activity estimation in preschoolers – comparison of cut-point sets incorporating the vector magnitude vs the vertical axis
- Published on May 6, 2019
ActiGraph accelerometers are a widely used tool to objectively measure physical activity (PA) behavior in young children and several validated cut-point sets exist to estimate time spent in different PA intensities (sedentary time, light PA, moderate-to-vigorous PA). Applying different cut-point sets leads to large and meaningful differences in results. So far, only cut-point sets validated for the vertical axis have been compared and only the influence on time spent in moderate-to-vigorous PA has been analyzed.
A range of validated cut-point sets with their respective epoch length was applied to analyze cross-sectional data of the Swiss Preschoolers’ Health Study (SPLASHY): 1) Vertical axis in combination with an epoch length of 15 s (VA-15), 2) Vertical axis in combination with an epoch length of 60 s (VA-60) and 3) Vector magnitude in combination with an epoch length of 60 s (VM-60). PA was measured for eight consecutive days using ActiGraph accelerometers (wGT3X-BT). Three days were required to be included in the analysis (minimum two weekdays and one weekend-day with at least ten hours recording per day).
Four hundred forty-five preschoolers (mean age 3.9 ± 0.5 years; 46% girls) had valid accelerometer measurements. A longer epoch (VA-60 vs VA-15) resulted in 2% less sedentary time (ST), 18% more light PA (LPA) and 51% less moderate-to-vigorous PA (MVPA); using the vector magnitude compared to the vertical axis (VM-60 vs VA-60) resulted in 34% less ST, 27% more LPA and 63% more MVPA (all p ≤ 0.001). Comparing all three sets of cut-points, ST ranged from 4.0 to 6.2 h, LPA from 5.1 to 7.6 h and MVPA from 0.8 to 1.6 h.
Estimated time spent in different PA intensities was strongly influenced by the choice of cut-point sets. Both, axis selection and epoch length need to be considered when comparing different studies especially when they relate PA behavior to health. The differences in the prevalence of children fulfilling PA guidelines highlight the relevance of these findings.
- Claudia S. Leeger-Aschmann 1
- Einat A. Schmutz 1
- Annina E. Zysset 2
- Tanja H. Kakebeeke 2,3
- Nadine Messerli-Bürgy 4,5
- Kerstin Stülb 6
- Amar Arhab 5
- Andrea H. Meyer 6,7
- Simone Munsch 6,8
- Oskar G. Jenni 2,3,8
- Jardena J. Puder 5,8
- Susi Kriemler 1,8
Child Development Center, University Children’s Hospital Zurich, Steinwiesstrasse 75, 8032, Zurich, Switzerland
Children’s Research Center, University Children’s Hospital Zurich, Steinwiesstrasse 75, 8032, Zurich, Switzerland
Clinical Child Psychology & Biological Psychology, University of Fribourg, Rue P.A. de Faucigny 2, 1700, Fribourg, Switzerland
Obstetric service, Department Woman-Mother-Child, Lausanne University Hospital, Avenue Pierre Decker 2, 1011, Lausanne, Switzerland
Department of Clinical Psychology and Psychotherapy, University of Fribourg, Rue P.A. de Faucigny 2, 1700, Fribourg, Switzerland
Department of Psychology, Division of Clinical Psychology and Epidemiology, University of Basel, Missionsstrasse 62A, 4055, Basel, Switzerland
Simone Munsch, Oskar G. Jenni, Jardena J. Puder and Susi Kriemler shared last authors
BMC Public Health