OBJECTIVE To derive accelerometer count thresholds for classifying time spent in sedentary, light-intensity and moderate-to-vigorous physical activity (MVPA) in manual wheelchair users (MWUs) with spinal cord injury (SCI). DESIGN Participants completed 18 activities of daily living and exercises for 10 minutes each with a 3-minute break between activities while wearing a Cosmed-k4b2 portable metabolic cart (COSMED, srl., Rome, Italy) and an ActiGraph activity monitor (ActiGraph, LLC., Pensacola, FL, USA) around the dominant wrist. A linear regression was computed between the wrist acceleration vector magnitude and SCI metabolic equivalent of task (MET) for 80% of the participants to obtain thresholds for classifying different activity intensities, while the obtained thresholds were tested for accuracy on the remaining 20% of participants. This cross-validation process was iterated for 1000 times to evaluate the stability of the thresholds on data corresponding to different proportions of sedentary, light-intensity, and MVPA. MET values ≤ 1.5 were classified as sedentary behavior, 1.5-3 METs were classified as light intensity, and ≥ 3 METs were classified as MVPA. The final thresholds were then validated on an out-of-sample independent dataset. PARTICIPANTS MWUs with SCI INTERVENTION: Not applicable SETTING: Research-lab, community MAIN OUTCOME MEASURES: Accelerometer thresholds to classify sedentary, light-intensity and MVPA were obtained and their accuracy tested using cross-validation as well as an out-of-sample dataset. RESULTS The thresholds between sedentary and light-intensity was 2,057 counts-per-minute, and between light-intensity and MVPA was 11,551 counts-per-minute. Based on the out-of-sample validation, the obtained thresholds had an overall accuracy of 85.6% with a sensitivity and specificity of 95.3% and 97.4% for sedentary behavior, 87.8% and 84.5% for light-intensity, 68.5% and 96.3% for MVPA, respectively. CONCLUSION Accelerometer-based thresholds can be used to identify sedentary behavior accurately, however thresholds may not provide accurate estimations of MVPA throughout the day when participants engage in more resistance-based activities.

中文翻译：

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使用腕戴式活动图监测器估计脊髓损伤中的体力活动强度

目的 推导出加速度计计数阈值，用于对患有脊髓损伤 (SCI) 的手动轮椅使用者 (MWU) 的久坐、轻度和中度到剧烈的体力活动 (MVPA) 花费的时间进行分类。设计参与者穿着 Cosmed-k4b2 便携式代谢手推车（COSMED, srl., Rome, Italy）和 ActiGraph 活动监测器（ActiGraph, LLC）完成了 18 项日常生活和锻炼活动，每次 10 分钟，活动之间休息 3 分钟., Pensacola, FL, USA) 围绕主导手腕。对 80% 的参与者的手腕加速度矢量幅度和 SCI 任务的代谢当量 (MET) 之间进行线性回归计算，以获得对不同活动强度进行分类的阈值，同时对其余 20% 的参与者测试获得的阈值的准确性. 这个交叉验证过程迭代了 1000 次，以评估对应于不同比例久坐、光照强度和 MVPA 的数据阈值的稳定性。MET 值≤ 1.5 被归类为久坐行为，1.5-3 MET 被归类为光强，≥ 3 MET 被归类为MVPA。然后在样本外独立数据集上验证最终阈值。SCI 干预的参与者 MWU：不适用 设置：研究实验室、社区 主要结果测量：获得了对久坐、光强度和 MVPA 进行分类的加速度计阈值，并使用交叉验证和样本外数据集测试了它们的准确性. 结果 久坐和光强度之间的阈值为 2,057 次/分钟，光强度和 MVPA 之间的阈值为 11,551 次/分钟。基于样本外验证，获得的阈值的总体准确率为 85.6%，久坐行为的敏感性和特异性分别为 95.3% 和 97.4%，光强度的敏感性和特异性分别为 87.8% 和 84.5%，68.5% 和 96.3%分别为MVPA。结论 基于加速度计的阈值可用于准确识别久坐行为，但是当参与者从事更多基于阻力的活动时，阈值可能无法提供全天 MVPA 的准确估计。