Physical activity (PA) and related energy expenditure (EE) is often assessed by means of a single technique. Because of inherent limitations, single techniques may not allow for an accurate assessment both PA and related EE. The aim of this study was to develop a model to accurately assess common PA types and durations and thus EE in free-living conditions, combining data from global positioning system (GPS) and 2 accelerometers.
Forty-one volunteers participated in the study. First, a model was developed and adjusted to measured EE with a first group of subjects (Protocol I, n = 12) who performed 6 structured and supervised PA. Then, the model was validated over 2 experimental phases with 2 groups (n = 12 and n = 17) performing scheduled (Protocol I) and spontaneous common activities in real-life condition (Protocol II). Predicted EE was compared with actual EE as measured by portable indirect calorimetry.
In protocol I, performed PA types could be recognized with little error. The duration of each PA type could be predicted with an accuracy below 1 minute. Measured and predicted EE were strongly associated (r = .97, P < .001).
Combining GPS and 2 accelerometers allows for an accurate assessment of PA and EE in free-living situations.
Nguyen and Lecoultre are with the Dept of Cell Biology and Morphology, Lausanne University, Lausanne, Switzerland. Sunami is with the Dept of Early Childhood Development, Fukuoka Jo Gakuin University, Fukuoka, Kasuga, Japan. Schutz is with the Dept of Physiology, Faculty of Medicine, University of Lausanne, Switzerland.