1 Department of Engineering, Aarhus University , Aarhus, Denmark .
2 Department of Orthopedic Surgery, Aarhus University Hospital , Aarhus, Denmark .
Telemed J E Health. 2018 Sep;24(9):669-677. doi: 10.1089/tmj.2017.0264. Epub 2018 Jan 5.
Activity trackers are useful tools for physical rehabilitation purposes. Most available activity trackers are designed for fitness and wellness use, lacking in both accuracy and precision at lower speeds. Validity and reliability at all clinically relevant speeds are crucial selection criteria for use in clinical practice. The aim of this study was to assess the validity and reliability of four consumer-based activity trackers at clinical relevant walking speeds for patient groups undergoing rehabilitation.
The four commercial activity trackers Fitbit Surge (FS), Fitbit Charge HR (FC), Microsoft Band 2 (MB), and A&D 101NFC Activity Monitor (A&D) were evaluated at 2, 4, 4.5, and 5.5 km/h. Twenty healthy participants aged 25.6 ± 2 years walked on a treadmill at the four velocities in two trials of 100 steps each. Mean average percentage error (MAPE), intraclass correlation coefficient (ICC), and Bland-Altman 95% limits of agreement were calculated to assess validity and reliability.
MAPE levels were between -8% and -6% for FS, -15% and 0% for MB, 7% and 21% for FC, and -53% and 1% for AD. The biggest inaccuracies were seen at 2 km/h, where AD underestimated by 53%. The highest accuracy was predominantly found with MB and AD, which overestimated ≤2% at velocities ≥4 km/h. ICC was moderate (0.73) for FS, good (0.88) for MB, moderate (0.52) for FC, and excellent (0.98) for AD.
MB, FS, and AD accurately counted steps, when participants walked with velocities corresponding to a brisk walk (≥4 km/h). Walking at lower speeds (≤2 km/h) was not counted accurately. Thus, the four evaluated activity trackers are not useful for patient groups walking at lower speeds during rehabilitation, nor for counting indoor walking.
活动追踪器是物理康复目的的有用工具。大多数可用的活动追踪器是为健身和健康使用而设计的，在较低速度下既不准确也不精确。在所有临床相关速度下的有效性和可靠性是在临床实践中使用的关键选择标准。本研究的目的是评估四种基于消费者的活动追踪器在临床相关步行速度下对接受康复治疗的患者群体的有效性和可靠性。
评估了四个商业活动追踪器 Fitbit Surge（FS）、Fitbit Charge HR（FC）、Microsoft Band 2（MB）和 A&D 101NFC 活动监视器（A&D）在 2、4、4.5 和 5.5 km/h 的速度下的性能。20 名年龄为 25.6±2 岁的健康参与者在跑步机上以四种速度各走 100 步，进行两次试验。计算平均平均百分比误差（MAPE）、组内相关系数（ICC）和 Bland-Altman 95%一致性界限，以评估有效性和可靠性。
FS 的 MAPE 水平在-8%和-6%之间，MB 在-15%和 0%之间，FC 在 7%和 21%之间，AD 在-53%和 1%之间。在 2 km/h 时，AD 的最大误差为 53%，低估了 53%。在速度≥4 km/h 时，MB 和 AD 主要表现出较高的准确性，高估≤2%。FS 的 ICC 为中度（0.73），MB 为良好（0.88），FC 为中度（0.52），AD 为优秀（0.98）。
当参与者以相当于快走（≥4 km/h）的速度行走时，MB、FS 和 AD 可以准确地计数步数。在较低速度（≤2 km/h）下行走时，无法准确计数。因此，在康复期间，评估的四个活动追踪器对于以较低速度行走的患者群体和室内行走都没有用处。
