Criterion Validity of Competing Accelerometry-Based Activity Monitoring Devices

The purpose of this study was to examine the comparative and criterion validity of the three activity monitors in relation to a portable metabolic analyzer (Oxycon Mobile (OM)) in adults.

A total of 52 adults age 18-40 yr each performed a series of 15 activities for 5 min each, with 1-min resting intervals between different activities. Participants completed the trials while wearing the three activity monitors and while being measured with the OM. Estimates of energy expenditure (EE) were obtained from the ActiGraph (one based on the vertical axis and the other from vector magnitude) as well as from the activPAL (AP) and the Core Armband (CA). The EE estimates were converted into MET(RMR) values by standardizing EE values with each person's resting metabolic rate and then temporarily matched to facilitate minute-by-minute comparisons. Equivalence testing and mean absolute percent errors (MAPE) were used to evaluate the agreement.

MET(RMR) values from the CA were significantly equivalent to those from the OM for the overall group comparison (90% confidence interval (CI), 3.65 and 3.85 MET(RMR)) and vigorous intensity (90% CI, 8.27 and 10.10 MET(RMR)). The CA had the smallest MAPE for moderate (20.7%) and vigorous (14.5%) intensity, but the AP had smaller MAPE for sedentary activities (27.4%) and light (24.7%) intensity activities.

The CA showed good agreement relative to the OM for the overall group comparison and for moderate and vigorous activities. The AP, in contrast, was the most accurate for sedentary and light activities. The combined use of the CA and AP may yield more accurate estimates of EE than using a single monitor.