How consumer physical activity monitors could transform human physiology research

Abstract

A sedentary lifestyle and lack of physical activity are well-established risk factors for chronic disease and adverse health outcomes. Thus, there is enormous interest in measuring physical activity in biomedical research. Many consumer physical activity monitors, including Basis Health Tracker, BodyMedia Fit, DirectLife, Fitbit Flex, Fitbit One, Fitbit Zip, Garmin Vivofit, Jawbone UP, MisFit Shine, Nike FuelBand, Polar Loop, Withings Pulse O2, and others have accuracies similar to that of research-grade physical activity monitors for measuring steps. This review focuses on the unprecedented opportunities that consumer physical activity monitors offer for human physiology and pathophysiology research because of their ability to measure activity continuously under real-life conditions and because they are already widely used by consumers. We examine current and potential uses of consumer physical activity monitors as a measuring or monitoring device, or as an intervention in strategies to change behavior and predict health outcomes. The accuracy, reliability, reproducibility, and validity of consumer physical activity monitors are reviewed, as are limitations and challenges associated with using these devices in research. Other topics covered include how smartphone apps and platforms, such as the Apple ResearchKit, can be used in conjunction with consumer physical activity monitors for research. Lastly, the future of consumer physical activity monitors and related technology is considered: pattern recognition, integration of sleep monitors, and other biosensors in combination with new forms of information processing.

Keywords: accelerometer; activity tracker; fitness trackers; wearable device.

Copyright © 2017 the American Physiological Society.

Figures

Fig. 1.

Rapid growth of research involving Fitbit activity monitors. The number per year of clinical studies listed in clinicaltrials.gov (A), publications in the Ovid Medline database that cite Fitbit in their abstracts (B), and grants in the NIH RePORTER database (C), as of November 9, 2016. The “Full Text View,” “Tabular View,” and “Study Results” were examined for each clinical trial result to ensure relevance and to avoid duplicates of study entries. The year recruitment began for each selected study was noted. For each result in Ovid MEDLINE, the title and abstract were examined to ensure relevance and to avoid duplication, and the year of publication was noted. The project number, project title, and abstract were examined for each result found in the NIH RePORTER database to ensure relevance and avoid duplication and the first year of project funding was noted.

Fig. 2.

Primary outcome measures of studies involving Fitbit activity monitors. The number of clinical trials as of November 10, 2016, in clinicaltrials.gov citing use of Fitbit for various primary outcomes, including quality of life (QOL), fitness (e.g., exercise capacity and walking distance), behavior (e.g., medical adherence, diet, abstinence, smoking), weight (e.g., body mass index, waist circumference, lean and fat muscle mass), feasibility (e.g., recruitment, retention, adherence, satisfaction), biomarker (e.g., blood pressure, heart rate, sleep, fasting insulin, HbA1c) and physical activity (e.g., step count, moderate to vigorous physical activity) (A) and biomarker primary outcomes, including autoimmune, sleep, cardio-pulmonary (Cardio-Pulm), metabolic function (Metabolic Fnct) and cognition and neurological (Cogn and Neuro) indicators (B), based on primary outcome categories listed in clinicaltrials.gov.