Accelerometry for measuring physical activity. Recommendations on methods

Accelerometry is an internationally well-established procedure for the objective measurement of habitual physical activity in large samples under free-living conditions and shows good psychometric properties. Accelerometers register the intensity and duration of single or multiaxial body acceleration. The duration of light, moderate and vigorous physical activity as well as sedentary time is calculated based on cutpoint models and energy expenditure is estimated by linear regression models. Nevertheless, the comparability of results between studies remains limited due to the use of different devices, protocols, calibration procedures and presentation of results. The recommendations, perspectives and limitations of accelerometer use described here have been collated and agreed by all members of the consensus group. Currently, there is no evidence for recommending a specific accelerometer model as model selection depends on the study question, target groups and study design. To obtain objective information on habitual physical activity behavior, a minimum wear time of 7 consecutive days with a minimum of 10 h/day including one weekend day is recommended. To avoid bias the selected epoch length should be as short as possible or raw data should be recorded. For adults, the cutpoint model of Freedson et al. (1998) for estimating different activity categories is well accepted. Methodological limitations include the recognition of activities with limited body acceleration, such as bicycling or weight training and the estimation of energy expenditure using only linear regression models.