Department of Biostatistics, Virginia Commonwealth University, Richmond, Virginia, United States of America.
Department of Internal Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America.
PLoS One. 2018 Apr 24;13(4):e0193467. doi: 10.1371/journal.pone.0193467. eCollection 2018.
Metabolic chambers are powerful tools for assessing human energy expenditure, providing flexibility and comfort for the subjects in a near free-living environment. However, the flexibility offered by the large living room size creates challenges in the assessment of dynamic human metabolic signals-such as those generated during high-intensity interval training and short-term involuntary physical activities-with sufficient temporal accuracy. Therefore, this paper presents methods to improve the temporal accuracy of metabolic chambers. The proposed methods include 1) adopting a shortest possible step size, here one minute, to compute the finite derivative terms for the metabolic rate calculation, and 2) applying a robust noise reduction method-total variation denoising-to minimize the large noise generated by the short derivative term whilst preserving the transient edges of the dynamic metabolic signals. Validated against 24-hour gas infusion tests, the proposed method reconstructs dynamic metabolic signals with the best temporal accuracy among state-of-the-art approaches, achieving a root mean square error of 0.27 kcal/min (18.8 J/s), while maintaining a low cumulative error in 24-hour total energy expenditure of less than 45 kcal/day (188280 J/day). When applied to a human exercise session, the proposed methods also show the best performance in terms of recovering the dynamics of exercise energy expenditure. Overall, the proposed methods improve the temporal resolution of the chamber system, enabling metabolic studies involving dynamic signals such as short interval exercises to carry out the metabolic chambers.
代谢室是评估人体能量消耗的有力工具，在接近自由生活环境的情况下为受试者提供了灵活性和舒适性。然而，大客厅尺寸提供的灵活性在评估动态人体代谢信号方面带来了挑战，例如在高强度间歇训练和短期非自愿体力活动期间产生的代谢信号，其时间准确性不足。因此，本文提出了提高代谢室时间准确性的方法。所提出的方法包括 1）采用尽可能短的步长，即一分钟，来计算代谢率计算的有限导数项，以及 2）应用稳健的降噪方法-全变差降噪，以最小化短导数项产生的大噪声，同时保留动态代谢信号的瞬态边缘。通过与 24 小时气体输注测试进行验证，所提出的方法在最先进的方法中重建动态代谢信号的时间准确性最佳，达到了 0.27 千卡/分钟（18.8 J/s）的均方根误差，同时保持了 24 小时总能量消耗的累积误差小于 45 千卡/天（188280 J/天）。当应用于人体运动测试时，所提出的方法在恢复运动能量消耗动态方面也表现出最佳性能。总体而言，所提出的方法提高了室系统的时间分辨率，使涉及短间隔运动等动态信号的代谢研究能够在代谢室中进行。
