differentiate between a reliable test and a valid test.

The devices helped to grow what is known as the Quantified Self movement, engaging those who wish to track their own personal data to optimize health behaviors. As new activity trackers and features are introduced to the market, documentation of the measurement properties can guide their use in research settings.Ĭonsumer wearable devices are a popular and growing market for monitoring physical activity, sleep, and other behaviors. The evidence reviewed indicated high interdevice reliability for steps, distance, energy expenditure, and sleep for certain Fitbit models.

This systematic review indicated higher validity of steps, few studies on distance and physical activity, and lower validity for energy expenditure and sleep. When wearing two Fitbits while sleeping, consistency between the devices was high. Walking- and running-based Fitbit trials indicated consistently high interdevice reliability for steps (Pearson and intraclass CC 0.76–1.00), distance (intraclass CC 0.90–0.99), and energy expenditure (Pearson and intraclass CC 0.71–0.97). Interdevice reliability was reported on seven studies using the Fitbit, but none for the Jawbone. No studies of intradevice reliability were found. Total sleep time and sleep efficiency were over-estimated and wake after sleep onset was under-estimated comparing metrics from polysomnography to either tracker using a normal mode setting. Using several different comparison measures (indirect and direct calorimetry, accelerometry, self-report), energy expenditure was more often under-estimated by either tracker. Two field-based studies compared accelerometry-assessed physical activity to the trackers, with one study finding higher correlation (Spearman CC 0.86, Fitbit) while another study found a wide range in correlation (intraclass CC 0.36–0.70, Fitbit and Jawbone). Only one study assessed distance for the Fitbit, finding an over-estimate at slower speeds and under-estimate at faster speeds. For laboratory-based studies using step counting or accelerometer steps, the correlation with tracker-assessed steps was high for both Fitbit and Jawbone (Pearson or intraclass correlation coefficients (CC) > =0.80). In total, 22 studies were included in the review (20 on adults, 2 on youth). Two people reviewed and abstracted each included study.

Searches included only full-length English language studies published in PubMed, Embase, SPORTDiscus, and Google Scholar through July 31, 2015. The purpose of this systematic review was to summarize the evidence for validity and reliability of popular consumer-wearable activity trackers (Fitbit and Jawbone) and their ability to estimate steps, distance, physical activity, energy expenditure, and sleep. Consumer-wearable activity trackers are electronic devices used for monitoring fitness- and other health-related metrics.

Differentiate between a reliable test and a valid test.