Validity of physical activity monitors during daily life in patients with COPD

Symptoms during physical activity (PA) and physical inactivity are hallmarks of COPD. Our aim was to evaluate the validity and usability of six activity monitors in patients with COPD against the doubly labelled water (DLW) indirect calorimetry method.Eighty COPD patients (age 68±6 years, FEV1 57±19% predicted) recruited in four centres each wore simultaneously three or four of six commercially available monitors validated in chronic conditions for 14 consecutive days. A priori validity criteria were defined. These included the ability to explain total energy expenditure (TEE) variance through multiple regression analysis, using TEE as the dependent variable with total body water (TBW) plus several PA monitors outputs as independent variables; and correlation with DLW measured activity energy expenditure (AEE).The Actigraph GT3X and DynaPort MoveMonitor best explained the majority of the TEE variance not explained by TBW (53% and 70% respectively) and showed the most significant correlations with AEE (r=0.71 p<0.001, r=0.70 p