There are no practical and valid methods for the assessment of individualised physical activity (PA) intensity in observational studies. Therefore, we investigated the validity of commonly used metabolic equivalent of tasks (METs) and pre-determined PA intensity classification methods against individualised PA intensity classification in 35 children 7–11-years-of-age. Then, we studied validity of mean amplitude deviation (MAD) measured by accelerometry during self-paced walking and running in assessment of individualised PA intensity. Individualised moderate PA (MPA) was defined as V̇O₂ ≥ 40% of V̇O_2reserve and V̇O₂ < ventilatory threshold (VT) and vigorous PA (VPA) as V̇O₂ ≥ VT. We classified > 3–6 (or alternatively > 4–7) METs as MPA and > 6 (> 7) METs as VPA. Task intensities were classified according to previous calibration studies. MET-categories correctly identified 25.9–83.3% of light PA, 85.9–90.3% of MPA, and 56.7–82.2% of VPA. Task-specific categories correctly classified 53.7% of light PA, 90.6% of MPA, and 57.8% of VPA. MAD during self-paced walking discriminated MVPA from light PA (sensitivity = 67.4, specificity = 88.0) and MAD during self-paced running discriminated VPA from MPA (sensitivity = 78.8, specificity = 79.3). In conclusion, commonly used methods may misclassify PA intensity in children. MAD during self-paced running may provide a novel and practical method for determining individualised VPA intensity in children.

在观察研究中，没有实用有效的方法来评估个体化的身体活动（PA）强度。因此，我们调查了35名7-11岁儿童中常用的代谢当量任务（METs）和预定的PA强度分类方法对个体PA强度分类的有效性。然后，我们研究了在自定步距和跑步过程中通过加速度计测量的平均幅度偏差（MAD）的有效性，以评估个人化PA强度。个性化的中度PA（MPA）定义为VO ₂  ≥Vo的40％_2reserve和VO ₂  <通气阈（VT）和剧烈PA（VPA）作为VO ₂ ≥VT。我们将> 3–6（或> 4–7）MET划分为MPA，并将> 6（> 7）MET划分为VPA。根据以前的校准研究对任务强度进行了分类。MET类别可正确识别轻型PA的25.9-83.3％，MPA的85.9-90.3％和VPA的56.7-82.2％。特定于任务的类别对轻型PA的53.7％，MPA的90.6％和VPA的57.8％进行了正确分类。自定步态行走时的MAD将轻度PA区分为MVPA（灵敏度= 67.4，特异性= 88.0），而自定步速行走时的MAD则将其与MPA区分了MVPA（灵敏度= 78.8，特异性= 79.3）。总之，常用的方法可能会错误分类儿童的PA强度。自定速度跑步过程中的MAD可能提供一种新颖实用的方法来确定儿童的个体VPA强度。