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Objective - Accelerometer

627. Validity of Consumer-Based Physical Activity Monitors

Research Article
Jung-Min Lee, Kim, Youngwon Kim, Gregory J. Welk
June 2014

Commentary: Rona Macniven, GlobalPAnet Executive, Prevention Research Collaboration, The University of Sydney

Over the past few years, we have witnessed the development of numerous new wearable devices to track, monitor and record physical activity. While such devices are marketed to provide personal information on the levels of physical activity and daily energy expenditure; few have undergone scientific validity testing to establish whether they measure activity accurately. This study assessed the validity of energy expenditure estimates of eight devices, finding an interesting range of accuracy across devices.

Sixty young men and women (aged 26 years on average) wore eight activity monitors concurrently; BodyMedia FIT armband worn on the left arm, DirectLife monitor around the neck, Fitbit One, Fitbit Zip, and ActiGraph worn on the belt and the Jawbone Up and Basis B1 band monitor on the wrist. The subjects had their resting energy expenditure measured during one laboratory visit, followed by a second visit to conduct measurements while wearing the devices. The validity of the energy expenditure estimates from each monitor was evaluated relative to criterion values concurrently obtained from a portable metabolic system. Differences from criterion measures were expressed as a mean absolute percent error (MAPE) and were evaluated using 95% equivalence testing.

The MAPE values ranged from the highest validity: 9.3% for the BodyMedia FIT; 10.1% for the Fitbit Zip through to the lowest; 23.5% for the Basis B1 band. Other values were 10.4% for the Fitbit One, 12.2% for the Jawbone Up, 12.6% for the Actigraph, 12.8% for the DirectLife and 13.0% for the NikeFuel Band. The results from the equivalence testing showed the estimates from the BodyMedia FIT, Fitbit Zip, and NikeFuel Band (90% CI: 341.1, 359.4) were each within the 10% equivalence zone around the indirect calorimetry estimate.

These findings give a useful indicator of the best devices to recommend to the general public, as well as to researchers, highlighting the best accuracy for the BodyMedia FIT, followed by the Fibit Zip. As newer devices will undoubtedly emerge in the future, validity testing of this sort will help determine their potential usefulness. 

Source: Medicine and Science in Sports and Exercise, 2014, Published Ahead of Print. Access to this article will depend on your institutional rights. Click here for the full article.