Methods for objective measure, quantification and analysis of sedentary behaviour and physical activity

International audienceThere is now increasing evidence that sedentary behaviour (SB) per se, rather than being a low level of physical activity (PA), represents behaviour that is partially independent of PA. This evidence has shown that it is necessary to study and quantify both behaviours simultaneously. Several studies have used objective measures of energy expenditure, recorded by accelerometers. These studies have reported a relationship between total time and some risk factors for health and sedentary life-style, as well as protective effects of the moderate PA. However, these results do not allow a better understanding of the factors that drive the adoption of a sedentary or active lifestyle. Global measures of sedentary time or PA are not sufficient to investigate them. Indeed, patterns of accumulation (i.e., frequency and duration) of sedentary life and PA have a substantial impact on different aspects of mental and physical health. Accelerometers offer the possibility to explore the temporal patterns of behaviour. A recent study found a relationship between the number of interruptions in sedentary periods and metabolic markers, illustrating the potential importance for the study of sedentary period patterns. Similarly, patterns of PA, particularly periods of at least 15 minutes per day of moderate PA, may contribute to a reduction in mortality risk. The objective of this communication is to present a generic method, via the alpha exponent (?) and the GINI index (G), for analysing and quantifying, regarding frequency and duration, objectively measured patterns of SB and PA. Finally, a presentation of the results of a study on these behavioural patterns will be briefly described and discussed