title: Assessment of energy expenditure for physical activity using a triaxial accelerometer.
abstract: A triaxial accelerometer was used to evaluate the relationship between energy expenditure due to physical activity (EEact) and body acceleration during different types of activity. In a laboratory experiment, 11 male subjects performed sedentary activities and walked on a motor driven treadmill (3-7 km.h-1). EEact was calculated from total energy expenditure (EEtot), as measured by indirect calorimetry, and sleeping metabolic rate (SMR): EEact = EEtot--SMR. Body accelerations were measured with a triaxial accelerometer at the low back. Special attention was paid to the analysis of unidirectional and three-directional accelerometer output. During sedentary activities a linear relationship between EEact and the sum of the integrals of the absolute value of accelerometer output from all three measurement directions (IAAtot) was found (r = 0.82, P < 0.001, Sy,x = 0.22 W.kg-1). During walking EEact was highly correlated with the integral of absolute accelerometer output in antero-posterior direction (IAAx; r = 0.96, P < 0.001, Sy,x = 0.53 W.kg-1). When all examined activities were included in a regression analysis, a strong linear relationship between EEact and IAAtot was found (r = 0.95, P < 0.001, Sy,x = 0.70 W.kg-1). Using this relationship, EEact during sedentary activities as well as EEact during walking could be estimated with an accuracy of about 15%. Although sedentary activities and walking represent a large part of normal daily physical activity, the validity and usefulness of the triaxial accelerometer--measuring IAAtot--to predict EEact in daily life must be studied under free-living conditions.
authors.affiliation: Faculty of Mechanical Engineering, Division of Fundamentals, Eindhoven University of Technology, The Netherlands.
authors.forename: C V
authors.initials: CV
authors.lastname: Bouten
authors.forename: K R
authors.initials: KR
authors.lastname: Westerterp
authors.forename: M
authors.initials: M
authors.lastname: Verduin
authors.forename: J D
authors.initials: JD
authors.lastname: Janssen
mesh_terms: D000054:Acceleration; D000328:Adult; D002151:Calorimetry / Q000379:methods; D004734:Energy Metabolism / Q000502:physiology*; D016552:Ergometry / Q000295:instrumentation; D005080:Exercise Test; D005544:Forecasting; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D011187:Posture / Q000502:physiology; D012044:Regression Analysis; D012146:Rest / Q000502:physiology; D012890:Sleep / Q000502:physiology; D016138:Walking / Q000502:physiology