Purpose: Using wearable monitoring devices is increasingly ubiquitous, including among young people. However, there is limited evidence of the validity of devices which are aimed at children and adolescents. The purpose of this study was to evaluate the validity of Fitbit Ace and Moki monitors in healthy young adolescents. Methods: This cross-sectional study included 17 young adolescents (ages 11–13 y) ambulating between 3 different walking conditions (incidental [∼6 min], controlled, and treadmill [each 3 min], while wearing wrist-worn devices [Fitbit Ace, Moki] on each wrist [left and right, respectively]). Data from the devices were compared with observer counts (criterion). Bland–Altman plots and mean absolute percentage errors were computed. Results: Analyses identified that the Fitbit Ace showed higher levels of bias across conditions compared with the Moki device: (mean difference [SD]; Fitbit Ace: 30.0 [38.0], 3.0 [13.0], and 13.0 [23.0] steps and Moki: 1.0 [19.0], 4.0 [16.0], and 6.0 [14.0] steps, incidental, controlled, and treadmill, respectively). Mean absolute percentage errors ranged from 3.1% to 9.5% for the Fitbit Ace and 3.0% to 4.0% for the Moki device. Conclusion: The Fitbit Ace and Moki devices might not provide acceptable validity under all walking conditions, but the Moki provides more accurate estimates of incidental walking and might therefore be a good choice for free-living research or school-based interventions.

目的：使用可穿戴监控设备越来越普遍，包括年轻人。然而，针对儿童和青少年的设备有效性的证据有限。本研究的目的是评估 Fitbit Ace 和 Moki 监测器在健康青少年中的有效性。方法：这项横断面研究包括 17 名青少年（11-13 岁），在 3 种不同步行条件（偶然 [~6 分钟]、受控和跑步机 [每 3 分钟]）之间行走，同时佩戴腕戴式设备 [Fitbit Ace, Moki] 在每个手腕上 [分别为左和右]）。将来自设备的数据与观察者计数（标准）进行比较。计算了 Bland-Altman 图和平均绝对百分比误差。结果：分析表明，与 Moki 设备相比，Fitbit Ace 在各种条件下显示出更高水平的偏差：（平均差 [S​​D]；Fitbit Ace：30.0 [38.0]、3.0 [13.0] 和 13.0 [23.0] 步，Moki：1.0 [19.0]、4.0 [16.0] 和 6.0 [14.0] 步，分别是偶然的、受控的和跑步机）。Fitbit Ace 的平均绝对百分比误差范围为 3.1% 至 9.5%，Moki 设备为 3.0% 至 4.0%。结论： Fitbit Ace 和 Moki 设备可能无法在所有步行条件下提供可接受的有效性，但 Moki 提供了更准确的偶然步行估计，因此可能是自由生活研究或基于学校的干预的良好选择。