Assessing the total energy expenditure (TEE) and the levels of physical activity in free-living conditions with non-invasive techniques remains a challenge. The purpose of the present study was to investigate the accuracy of a new uniaxial accelerometer for assessing TEE and physical-activity-related energy expenditure (PAEE) over a 24 h period in a respiratory chamber, and to establish activity levels based on the accelerometry ranges corresponding to the operationally defined metabolic equivalent (MET) categories. In study 1, measurement of the 24 h energy expenditure of seventy-nine Japanese subjects (40 (SD 12) years old) was performed in a large respiratory chamber. During the measurements, the subjects wore a uniaxial accelerometer (Lifecorder; Suzuken Co. Ltd, Nagoya, Japan) on their belt. Two moderate walking exercises of 30 min each were performed on a horizontal treadmill. In study 2, ten male subjects walked at six different speeds and ran at three different speeds on a treadmill for 4 min, with the same accelerometer. O 2 consumption was measured during the last minute of each stage and was expressed in MET. The measured TEE was 8447 (SD 1337) kJ/d. The accelerometer significantly underestimated TEE and PAEE (91·9 (SD 5·4) and 92·7 (SD 17·8) % chamber value respectively); however, there was a significant correlation between the two values (r 0·928 and 0·564 respectively; P, 0·001). There was a strong correlation between the activity levels and the measured MET while walking (r 2 0·93; P, 0·001). Although TEE and PAEE were systematically underestimated during the 24 h period, the accelerometer assessed energy expenditure well during both the exercise period and the non-structured activities. Individual calibration factors may help to improve the accuracy of TEE estimation, but the average calibration factor for the group is probably sufficient for epidemiological research. This method is also important for assessing the diurnal profile of physical activity.
Accelerometer: Daily energy expenditure: Physical activity: Respiration chamberThe energy expenditure (EE) associated with physical activity has a negative relationship with the prevalence of obesity and its related diseases (i.e. diabetes, hypertension, CVD etc.), and it plays a major role in the prevention and treatment of these diseases (Weinsier et al. 1998;Levine et al. 1999;Ravussin & Bogardus, 2000). When treatment strategies, including nutritional education, for those diseases are developed, quantitative information related to physical activity is required to provide more effective goals. Hence, information on physical activity is considered to be useful, not only for researchers and healthcare workers, but also for the general public, in order to prevent and treat these diseases more effectively.Activity monitoring based on an accelerometry sensor is one of the useful methods for obtaining objective information on physical activity patterns and for estimation * Corresponding author: Dr Yves Schutz, fax þ 41 21 692 55 95, email Yves.Schutz@...