Abstract
BackgroundWearables for monitoring physical activity (PA) are increasingly popular. These devices are not only used by consumers to monitor their own levels of PA but also by researchers to track the behavior of large samples. Consequently, it is important to explore how accurately PA can be tracked via these devices.ObjectivesThe aim of this study was, therefore, to investigate convergent validity of 3 Android Wear smartwatches—Polar M600 (Polar Electro Oy, Kempele, Finland), Huawei Watch (Huawei Technologies Co, Ltd, Shenzhen, Guangdong, China), Asus Zenwatch3 (AsusTek Computer Inc, Taipei, Taiwan)—and Fitbit Charge with an ActiGraph accelerometer for measuring steps and moderate to vigorous physical activity (MVPA) on both a day level and 15-min level.MethodsA free-living protocol was used in which 36 adults engaged in usual daily activities over 2 days while wearing 2 different wearables on the nondominant wrist and an ActiGraph GT3X+ accelerometer on the hip. Validity was evaluated on both levels by comparing each wearable with the ActiGraph GT3X+ accelerometer using correlations and Bland-Altman plots in IBM SPSS 24.0.ResultsOn a day level, all devices showed strong correlations (Spearman r=.757-.892) and good agreement (interclass correlation coefficient, ICC=.695-.885) for measuring steps, whereas moderate correlations (Spearman r=.557-.577) and low agreement (ICC=.377-.660) for measuring MVPA. Bland-Altman revealed a systematic overestimation of the wearables for measuring steps but a variation between over- and undercounting of MVPA. On a 15-min level, all devices showed strong correlations (Spearman r=.752-.917) and good agreement (ICC=.792-.887) for measuring steps, whereas weak correlations (Spearman r=.116-.208) and low agreement (ICC=.461-.577) for measuring MVPA. Bland-Altman revealed a systematic overestimation of the wearables for steps but under- or overestimation for MVPA depending on the device.ConclusionsIn sum, all 4 consumer-level devices can be considered accurate step counters in free-living conditions. This study, however, provides evidence of systematic bias for all devices in measurement of MVPA. The results on a 15-min level also indicate that these devices are not sufficiently accurate to provide correct real-time feedback.
Highlights
BackgroundPhysical inactivity is one of the major risk factors for mortality worldwide, causing an estimated 3.2 million deaths (6%) [1]
This study investigated the validity of 4 wearables (3 smartwatches and 1 activity tracker) for measuring steps and moderate to vigorous physical activity (MVPA) in naturalistic situations
It can be concluded that all 4 consumer-level devices (Huawei Watch, Polar M600, Asus ZenWatch2, and Fitbit Charge) are valid devices to estimate the amount of steps in naturalistic situations on both a day level and 15-min level
Summary
BackgroundPhysical inactivity is one of the major risk factors for mortality worldwide, causing an estimated 3.2 million deaths (6%) [1]. Adults aged 18 to 64 years should accumulate at least 150 min of moderate-intensity aerobic PA throughout the week or do at least 75 min of vigorous-intensity aerobic PA throughout the week or an equivalent combination of moderate and vigorous intensity activity [5,6] Another recommendation is to take at least 10,000 steps a day [7,8]. Wearables for monitoring physical activity (PA) are increasingly popular These devices are used by consumers to monitor their own levels of PA and by researchers to track the behavior of large samples. Results: On a day level, all devices showed strong correlations (Spearman r=.757-.892) and good agreement (interclass correlation coefficient, ICC=.695-.885) for measuring steps, whereas moderate correlations (Spearman r=.557-.577) and low agreement (ICC=.377-.660) for measuring MVPA. The results on a 15-min level indicate that these devices are not sufficiently accurate to provide correct real-time feedback
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