Estimating instantaneous energetic cost during non-steady-state gait
Estimating instantaneous energetic cost during non-steady-state gait
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DOI：
10.1152/japplphysiol.00445.2014
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发表时间：
2014-12-01
影响因子：
3.3
通讯作者：
Donelan, J. Maxwell
中科院分区：
文献类型：
--
作者：
Selinger, Jessica C.;Donelan, J. Maxwell
氧气和二氧化碳的呼吸测量通常用于估计身体的稳态代谢能量消耗。然而，缓慢的线粒体动力学、较长的传输时间、复杂的呼吸控制机制和较高的每次呼吸变异性掩盖了身体瞬时能量需求（瞬时能量成本）与呼吸气体测量的能量需求（测量的能量成本）之间的关系。本研究的目的是通过估计非稳态条件下的瞬时能量成本来扩展评估代谢成本的传统方法。为了实现这一目标，我们首先对能量使用（输入）施加已知的变化，同时测量每次呼吸的反应（输出）。我们使用这些输入/输出关系将身体建模为一个动态系统，将瞬时映射到测量的能量成本。我们发现一阶线性微分方程很好地近似了步态期间的瞬态能量成本响应。在所有受试者中，模型拟合参数化为 42 +/- 12 s 的平均时间常数 (tau)，平均 R-2 为 0.94 +/- 0.05（平均值 +/- SD）。有了这个输入/输出模型，我们接下来测试了是否可以使用它在模拟动态变化步态的条件下通过每次呼吸测量来可靠地估计瞬时能量消耗。强加的能量成本概况和我们估计的瞬时成本的比较表明了密切的对应关系，支持使用我们的方法来研究能量在运动适应和学习过程中的作用。
Respiratory measures of oxygen and carbon dioxide are routinely used to estimate the body's steady-state metabolic energy use. However, slow mitochondrial dynamics, long transit times, complex respiratory control mechanisms, and high breath-by-breath variability obscure the relationship between the body's instantaneous energy demands (instantaneous energetic cost) and that measured from respiratory gases (measured energetic cost). The purpose of this study was to expand on traditional methods of assessing metabolic cost by estimating instantaneous energetic cost during non-steady-state conditions. To accomplish this goal, we first imposed known changes in energy use (input), while measuring the breath-by-breath response (output). We used these input/output relationships to model the body as a dynamic system that maps instantaneous to measured energetic cost. We found that a first-order linear differential equation well approximates transient energetic cost responses during gait. Across all subjects, model fits were parameterized by an average time constant (tau) of 42 +/- 12 s with an average R-2 of 0.94 +/- 0.05 (mean +/- SD). Armed with this input/output model, we next tested whether we could use it to reliably estimate instantaneous energetic cost from breath-by-breath measures under conditions that simulated dynamically changing gait. A comparison of the imposed energetic cost profiles and our estimated instantaneous cost demonstrated a close correspondence, supporting the use of our methodology to study the role of energetics during locomotor adaptation and learning.