Carrying loads: validating a portable tri-axial accelerometer during frequent and brief physical activity

Abstract

Objectives The aim of this study is to evaluate the validity of the SenseWear Armband™ (SWA, Model MF-SW, BodyMedia Inc.) as a tool to assess daily brief, light- to moderate-intensity activities. Design A total of 41 volunteers were recruited (27 males, 14 females) to perform several trials, including a resting metabolic rate test and a number of walking trials while carrying different loads in a backpack. Methods Energy expenditure during trials was measured using both the SWA™ mini device, with the indirect calorimetry method (MasterScreen CPX and Oxycon Mobile JAEGER™ devices) used for validated comparative measurement. Results The SWA™ mini shows agreement with indirect calorimetry in all trials. However, the SWA™ mini over-estimated expenditure in all participants. Individual assessment estimates with the SWA™ mini also exhibited random errors. The variations in energy expenditure (EE) resulting from increased carried loads during the trials were not statistically significant when EE was measured with the SWA™ mini. Furthermore, Metabolic Equivalent of Task (MET) calculation, highly dependent on estimated energy expenditure per unit time, also was likely overestimated. In contrast, the SWA™ mini provided estimates of the resting metabolic rate with a small error. Conclusions The SWA™ mini is not a valid device for estimating energy expenditure in brief light- or moderate activities.