Schneider Margaret, Chau Larissa
Social Ecology I, University of California, Irvine, Irvine, CA, 92697, USA.
BMC Res Notes. 2016 Sep 21;9(1):448. doi: 10.1186/s13104-016-2253-6.
The widespread availability of affordable consumer-oriented devices for monitoring physical activity offers an appealing option to physical activity researchers, but studies are needed to demonstrate the validity and reliability of these products. To examine the validity of the Fitbit Zip, we recruited three cohorts (N's = 25, 35, and 27) of middle-school students to wear the Fitbit and the ActiGraph simultaneously for a week. Adolescents were healthy volunteers representing a range of activity levels. Mean daily minutes of MVPA and mean steps per day were compared between the Fitbit Zip and the Actigraph.
The step data for the Fitbit Zip correlated highly with the step data yielded by the ActiGraph (r's = .72, .92, .96), and the MVPA data for the Fitbit Zip correlated highly with the MVPA data from the ActiGraph (r's = .67, .79, .94). Bland-Altman plots revealed that the Fitbit Zip overestimated activity in comparison to the ActiGraph, especially for Cohort One, which completed the study before Fitbit modified their algorithms to count as activity only bouts that continued for at least 10 min.
Our data suggest that the Fitbit Zip is a reasonable alternative to the ActiGraph for estimating activity among free-living adolescents. However, data from the Fitbit should not be used interchangeably with data from the ActiGraph, as there is a consistent tendency for the Fitbit to overestimate steps in comparison to the ActiGraph. Also, the findings confirm concern about using for research a consumer-oriented device that does not make public their algorithms.
面向消费者的经济实惠的身体活动监测设备广泛可得，这为身体活动研究人员提供了一个有吸引力的选择，但需要研究来证明这些产品的有效性和可靠性。为了检验Fitbit Zip的有效性，我们招募了三组（人数分别为25、35和27）中学生，让他们同时佩戴Fitbit和ActiGraph一周。这些青少年是代表不同活动水平的健康志愿者。比较了Fitbit Zip和ActiGraph之间的每日平均中等至剧烈身体活动（MVPA）分钟数和每日平均步数。
Fitbit Zip的步数数据与ActiGraph得出的步数数据高度相关（相关系数分别为0.72、0.92、0.96），Fitbit Zip的MVPA数据与ActiGraph的MVPA数据高度相关（相关系数分别为0.67、0.79、0.94）。布兰德-奥特曼图显示，与ActiGraph相比，Fitbit Zip高估了活动量，尤其是对于第一组，该组在Fitbit修改其算法以仅将持续至少10分钟的运动视为活动之前就完成了研究。
我们的数据表明，在估计自由生活青少年的活动量方面，Fitbit Zip是ActiGraph的合理替代品。然而，Fitbit的数据不应与ActiGraph的数据互换使用，因为与ActiGraph相比，Fitbit始终有高估步数的倾向。此外，研究结果证实了人们对使用不公开其算法的面向消费者的设备进行研究的担忧。
