Accurate measurements of physical activity in free living are needed to establish what dose of physical activity is necessary for obtaining a specific health benefits. The first aim of this work was to validate the Actiheart (which combines heart rate and accelerometry sensors) with doubly labeled water (DLW). We show a good level of concordance between physical activity energy expenditure (PAEE) estimated by Actiheart and DLW. Individualization of the relationship between heart rate and PAEE by an incremental test is needed for an accurate estimate of the PAEE at the individual level and to evaluate changes induced by an intervention. In laboratory, we show that the accuracy of Actiheart is activitydependent. This requires the establishment of their recognition from new sensors and mathematical models. Adiponectin, hormone secreted by adipose tissue, has a role in energy metabolism and its secretion decreases with obesity. However the effects of physical activity remain in contradiction in published studies. The second objective of this work was to evaluate the effect of physical activity and intervention with weight control on plasma adiponectin. We show that the total and high molecular weight adiponectin were negatively associated with modifications of the physical activity level. Further work is however necessary to understand the mechanisms underlying this modulation of plasma adiponectin which does not seem related to changes in synthesis in adipose tissue or muscle.
