Investigation of an innovative activity tracking device: Advancing the science of wearable activity monitors

Abstract

Purpose:An innovative monitoring tool,the Metria IH1 Wearable Sensor,has been developed by Vancive Medical Technologies(Avery Dennison) in partnership with Bodymedia/Jawbone.The Metria is a non-invasive,disposable and water-resistant activity tracking monitor,equipped with multiple sensors plus a tri-axis accelerometer.However,little is known about the utility and accuracy of the Metria under free-living environments for adults.Therefore,the purpose of this research was to evaluate the performance of the Metria compared to existing monitoring technology,Core Armband,in adults.Methods:A total of 29 healthy adults ages 18 yrs and older wore one Metria and one Core for7 days.The Metria and Core were both worn on the back of the left upper arm,and the Metria was placed above the Core.Each participant was asked to visit the laboratory three times within the given week(Day 1,4,and 8) to undertake a proposed series of study protocol.Skin reactions to the monitors were visually inspected on each visit.Data from both the Metria and Core were coOected and downloaded on a minute-by-minute basis for temporal matching.The first and last day of measured days were excluded from analyses since the monitors were not worn by the participants for a complete 24 hour period.Any days with less than 90%of wear time per day were excluded.A 95%equivalence test was employed to evaluate overall agreement between the Metria and Core.Mean absolute percent error(MAPE) was calculated by dividing an absolute difference between the Metria and the Core by the Core,multiplied by 100%.MAPE values were used to evaluate individual level agreement.Pearson correlation coefficients were calculated to examine overall relationships between the two monitors.Results:Results from the equivalence testing indicated an equivalency of the Metria(90%confidence intervals;2679.3 and 2793.7 kcal) in relation to the Core(zone of equivalence;2490.3and 3043.7 kcal).A minimal MAPE(i.e.7.2%) was observed for the Metria,indicating a small individual level measurement error relative to the Core.A significant positive linear relationship between the Metria and Core was observed,with a correlation of 0.90 and a corresponding p-value<0.0001.The majority of the participants indicated the Metria being comfortable to wear and easy to use.Conclusion'.Overall,the Metria exhibited excellent agreement with the Core,a widely used objective monitoring tool.The Metria has the great potential to be utilized by physicians/medical doctors in clinical settings.Future research is warranted to examine the usability and validity of the Metria in relation to a gold-standard reference in various populations.