Objectives: The Activity Watch 200 (AW200) is a new device which calculates energy expenditure (EE) based on movement detection. We aimed to validate EE measured by this device against indirect calorimetry (IC) and to assess the reproducibility of AW200 measurements.
Design: EE was assessed during a 9.7 km hike. Twenty 35-45 year old men (10) and women (10), and 11 50-55 year old men (5) and women (6) were tested. One in five subjects of each age and sex matched group was equipped with a portable metabograph (Oxycon Mobil) for IC measurements. Data were collected every 30 minutes during the hike and IC was extrapolated for the remaining 4 other subjects of the group.
Results: During the total hike there was a high correlation between EE obtained from the AW200 and the IC calculation (r=0.987, P<0.001). Identical values of EE were calculated by both methods during the first 90min of the hike. However, EE calculated by the AW200 at 120min and at the end of the hike was lower (P<0.05). Bland-Altman analysis showed limits of agreements between 105 and 279 kJ after 30min and 120min, respectively. EE measured by the AW200 was well correlated with IC measurements and limits of agreement between devices are below 10% of the measured values for hike durations longer than 60min.
Conclusion: The AW200 appears to be a very useful and accurate device for measuring EE during exercise in recreational hikers and provides a useful tool for keeping track of personal energy expenditure.
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