Lai N, Dash R K, Nasca M M, Saidel G M, Cabrera M E
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106-6011, USA.
Eur J Appl Physiol. 2006 Jul;97(4):380-94. doi: 10.1007/s00421-006-0176-y. Epub 2006 Apr 25.
Assessment of the rate of muscle oxygen consumption, UO(2m), in vivo during exercise involving a large muscle mass is critical for investigating mechanisms regulating energy metabolism at exercise onset. While UO(2m) is technically difficult to obtain under these circumstances, pulmonary oxygen uptake, VO(2p), can be readily measured and used as a proxy to UO(2m). However, the quantitative relationship between VO(2p) and UO(2m) during the nonsteady phase of exercise in humans, needs to be established. A computational model of oxygen transport and utilization--based on dynamic mass balances in blood and tissue cells--was applied to quantify the dynamic relationship between model-simulated UO(2m) and measured VO(2p) during moderate (M), heavy (H), and very heavy (V) intensity exercise. In seven human subjects, VO(2p) and muscle oxygen saturation, StO(2m), were measured with indirect calorimetry and near infrared spectroscopy (NIRS), respectively. The dynamic responses of VO(2p) and StO(2m) at each intensity were in agreement with previously published data. The response time of muscle oxygen consumption, tauUO(2m) estimated by direct comparison between model results and measurements of StO(2m) was significantly faster (P < 0.001) than that of pulmonary oxygen uptake, tauVO(2p) (M: 13 +/- 4 vs. 65 +/- 7 s; H: 13 +/- 4 vs. 100 +/- 24 s; V: 15 +/- 5 vs. 82 +/- 31 s). Thus, by taking into account the dynamics of oxygen stores in blood and tissue and determining muscle oxygen consumption from muscle oxygenation measurements, this study demonstrates a significant temporal dissociation between UO(2m) and VO(2p) at exercise onset.
评估在涉及大量肌肉群的运动过程中体内肌肉耗氧率（UO₂m），对于研究运动开始时调节能量代谢的机制至关重要。虽然在这些情况下技术上难以获得UO₂m，但肺摄氧量（VO₂p）可以很容易地测量并用作UO₂m的替代指标。然而，需要建立人体运动非稳定阶段VO₂p与UO₂m之间的定量关系。基于血液和组织细胞中的动态质量平衡的氧运输和利用计算模型，被用于量化在中等强度（M）、高强度（H）和极高强度（V）运动期间模型模拟的UO₂m与测量的VO₂p之间的动态关系。在七名人类受试者中，分别使用间接量热法和近红外光谱法（NIRS）测量VO₂p和肌肉氧饱和度（StO₂m）。每个强度下VO₂p和StO₂m的动态反应与先前发表的数据一致。通过直接比较模型结果和StO₂m测量值估计的肌肉耗氧反应时间tauUO₂m，明显快于肺摄氧反应时间tauVO₂p（P < 0.001）（M：13±4 vs. 65±7秒；H：13±4 vs. 100±24秒；V：15±5 vs. 82±31秒）。因此，通过考虑血液和组织中氧储备的动态变化，并根据肌肉氧合测量确定肌肉耗氧量，本研究证明了运动开始时UO₂m和VO₂p之间存在显著的时间差异。
