Wrist-worn triaxial accelerometry predicts the energy expenditure of non-vigorous daily physical activities.
OBJECTIVE
Triaxial accelerometry is commonly used to estimate oxygen uptake (VO2) and energy expenditure in health and fitness studies. We tested the correlation of a triaxial accelerometer in terms of a summation of vector magnitudes with gravity subtracted (SVMgs) and measured VO2for different daily physical activities.


METHODS
Original research, cross-sectional.


METHODS
Twenty volunteers wore a triaxial accelerometer on both wrists while performing 12 assigned daily physical activities for 6min for each activity. The VO2was determined by indirect calorimetry using a portable metabolic measurement system. The last 3min of each activity was assumed to represent steady-state. The VO2measured during these periods was averaged and converted into metabolic equivalents (METs).


RESULTS
The range of VO2for all activities was 0.18-3.2L/min (0.8-12.2 METs). Significant differences in SVMgs existed between accelerometer placements on the dominant (120.9±8.7gmin) versus non-dominant hand (99.9±6.8gmin; P=0.016) for the lowest levels of physical activity defined as <1.5 METs. Piecewise linear regression model using 6 METs as the transition point showed similar significant correlations for the non-dominant wrist (r2=0.85; P<0.001) and the dominant wrist (r2=0.86; P<0.001). Using the non-dominant wrist below 6 METs, the slope of the relationship between SVMgs and METs was 105.3±4.3 (95% CI 96.9 to 113.7) indicating an increase in SVMgs of approximately 100 units for every MET increase in oxygen uptake.


CONCLUSIONS
Wrist-worn triaxial accelerometry reliably predicted energy expenditure during common physical activities <6 METs. More consistent correlations were found when the accelerometer was worn on the non-dominant wrist rather than the dominant wrist.
Exercise Physiology Research Laboratory, Departments of Medicine and Physiology, David Geffen School of Medicine, University of California at Los Angeles, USA; Division of Pulmonary and Critical Care Medicine, Department of Medicine, Faculty of Medicine, Chulalongkorn University, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Thailand.
Worawan
W
Sirichana
Exercise Physiology Research Laboratory, Departments of Medicine and Physiology, David Geffen School of Medicine, University of California at Los Angeles, USA.
Brett A
BA
Dolezal
Exercise Physiology Research Laboratory, Departments of Medicine and Physiology, David Geffen School of Medicine, University of California at Los Angeles, USA.
Eric V
EV
Neufeld
Division of General Internal Medicine and Health Services Research, David Geffen School of Medicine, University of California at Los Angeles, USA.
Xiaoyan
X
Wang
Exercise Physiology Research Laboratory, Departments of Medicine and Physiology, David Geffen School of Medicine, University of California at Los Angeles, USA. Electronic address: ccooper@mednet.ucla.edu.
Christopher B
CB
Cooper
D061725:Accelerometry / Q000295:instrumentation*; D000328:Adult; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D055686:Metabolic Equivalent / Q000502:physiology; D009043:Motor Activity / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D000076251:Wearable Electronic Devices; D014953:Wrist; D055815:Young Adult
Energy expenditure; Oxygen uptake; Physical activity; Triaxial accelerometer