Health through Physical Activity, Lifestyle and Sport Research Centre & Division of Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, South Africa.
Physiol Meas. 2020 Sep 4;41(8):085001. doi: 10.1088/1361-6579/aba80f.
The Actiwatch 2 (AW2) is a wrist-worn accelerometer typically used to measure sleep. Although it can measure physical activity, there is limited evidence supporting its validity. We assessed the validity and reliability of the AW2 to measure sedentary behavior and physical activity (light, moderate, vigorous intensities), and reported their respective count cut-points.
Twenty-eight males and 22 females completed a task battery comprising three sedentary tasks and six randomized physical activity tasks at varying intensities, whilst wearing the AW2, a reference accelerometry device (Actigraph GT3X) and a cardiopulmonary gas analyzer on two separate occasions. Validity was assessed using correlations (AW2 counts versus GT3X counts and metabolic equivalent (MET) values), reliability using Bland-Altman analyses, and cut-points were determined using receiver operating characteristic (ROC) area under the curve (AUC) analyses.
AW2 counts were positively correlated with GT3X counts (rho = 0.902, p < 0.001) and METs (rho = 0.900, p < 0.001). AW2-derived counts were comparable across independent assessment periods. Sedentary (AUC = 0.99, cut-point: 256 cpm) and vigorous activity (AUC = 0.95, cut-point: 720 cpm) were strongly characterized, and moderate activity (AUC = 0.66, cut-point: 418 cpm) was weakly characterized.
The use of the AW2 in physical activity monitoring looks promising for sedentary behavior, moderate and vigorous activity, however, further validation is needed.
Actiwatch 2（AW2）是一种通常用于测量睡眠的腕戴式加速度计。尽管它可以测量身体活动，但支持其有效性的证据有限。我们评估了 AW2 测量久坐行为和身体活动（低强度、中强度、高强度）的有效性和可靠性，并报告了各自的计步器计数切点。
28 名男性和 22 名女性在两次不同的场合，佩戴 AW2、参考加速度计设备（Actigraph GT3X）和心肺气体分析仪，完成了一个由三个久坐任务和六个随机身体活动任务组成的任务电池，任务强度不同。使用相关性（AW2 计数与 GT3X 计数和代谢当量（MET）值）评估有效性，使用 Bland-Altman 分析评估可靠性，使用接收器操作特征（ROC）曲线下面积（AUC）分析确定切点。
AW2 计数与 GT3X 计数（rho = 0.902，p < 0.001）和 METs（rho = 0.900，p < 0.001）呈正相关。AW2 衍生计数在独立评估期间具有可比性。久坐（AUC = 0.99，切点：256 cpm）和剧烈活动（AUC = 0.95，切点：720 cpm）特征明显，而中等强度活动（AUC = 0.66，切点：418 cpm）特征较弱。
AW2 在身体活动监测中的使用对于久坐行为、中高强度活动具有良好的应用前景，但需要进一步验证。
