Conclusions : We conclude that there is large heterogeneity across studies in the explained variance of AEE when estimated based on accelerometry .
Background / Objectives : Activity-related energy expenditure ( AEE ) might be an important factor in the etiology of chronic diseases .
However , measurement of free-living AEE is usually not feasible in large-scale epidemiological studies but instead has traditionally been estimated based on self-reported physical activity .
Accuracy of a combined heart rate and motion sensor for assessing energy expenditure in free-living adults during a double-blind crossover caffeine trial using doubly labeled water as the reference method
Background / Objectives : A combined heart rate ( HR ) and motion sensor ( Actiheart ) has been proposed as an accurate method for assessing total energy expenditure ( TEE ) and physical activity energy expenditure ( PAEE ) . However , the extent to which factors such as caffeine may affect the accuracy by which the estimated HR-related PAEE contribution will affect TEE and PAEE estimates is unknown . Therefore , we examined the validity of Actiheart in estimating TEE and PAEE in free-living adults under a caffeine trial compared with doubly labeled water ( DLW ) as reference criterion . Subjects/ Methods : Using a double-blind crossover trial ( Clinical trials.gov ID : # NCT01477294 ) with two conditions ( 4-day each with a 3-day-washout period ) , r and omly ordered as caffeine ( 5 mg/kg per day ) and placebo ( malt-dextrine ) intake , TEE was measured by DLW in 17 physically active men ( 20–38 years ) who were non-caffeine users . In each condition , resting energy expenditure ( REE ) was assessed by indirect calorimetry and PAEE was calculated as ( TEE−(REE+0.1 TEE ) ) . Simultaneously , PAEE and TEE were estimated by Actiheart using an individual calibration ( ACC+HRstep ) . Results : Under caffeine , ACC+HRstep explained 76 and 64 % of TEE and PAEE from DLW , respectively ; corresponding results for the placebo condition were 82 and 66 % . No mean bias was found between ACC+HRstep and DLW for TEE  ( caffeine:-468 kJ per day ; placebo:-407 kJ per day ) , although PAEE was slightly underestimated ( caffeine:-856 kJ per day ; placebo:-1147 kJ per day ) . Similar limits of agreement were observed in both conditions ranging from −2066 to 3002 and from −3488 to 1776 kJ per day for TEE and PAEE , respectively . Conclusions : Regardless of caffeine intake , the combined HR and motion sensor is valid for estimating free-living energy expenditure in a group of healthy men but is less accurate for an individual assessment
Conclusions : We conclude that there is large heterogeneity across studies in the explained variance of AEE when estimated based on accelerometry .
Background / Objectives : Activity-related energy expenditure ( AEE ) might be an important factor in the etiology of chronic diseases .
However , measurement of free-living AEE is usually not feasible in large-scale epidemiological studies but instead has traditionally been estimated based on self-reported physical activity .