Comparison of wrist-worn and hip-worn activity monitors under free living conditions.

PURPOSE: Current recommendations state that individuals engage in 150 min of moderate or 75 min of vigorous intensity physical activity (PA) each week. Commercial PA monitors are becoming popular for everyday use. The accuracy of these devices, however, is not well understood. We sought to examine the accuracy of two commercial devices, one wrist and one hip-worn, under free-living conditions.

METHODS: Twenty-two subjects wore two commercially available devices and one ActiGraph (AG) for seven consecutive days under normal activity.

RESULTS: Mean steps per day between all three devices differed significantly. No differences were found in moderate-to-vigorous intensity physical activity (MPVA). Daily energy expenditure (EE) also differed significantly between the AG and the commercial devices. Bland-Altman analysis found poor agreement between the AG and the commercial devices with regards to steps and EE, but good agreement in MVPA.

CONCLUSION: Results suggest that the commercial devices are less accurate in estimating steps and EE. These devices did show good agreement with regards to MVPA, suggesting that they may provide useful feedback for individuals seeking to achieve the current PA guidelines for MVPA. Improvements are needed with regards to steps and EE estimation.