Billinger Sandra A, Craig Jesse C, Kwapiszeski Sarah J, Sisante Jason-Flor V, Vidoni Eric D, Maletsky Rebecca, Poole David C
Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas;
Department of Kinesiology, Kansas State University, Manhattan, Kansas.
J Appl Physiol (1985). 2017 May 1;122(5):1125-1133. doi: 10.1152/japplphysiol.00995.2016. Epub 2017 Mar 9.
The dynamic response to a stimulus such as exercise can reveal valuable insights into systems control in health and disease that are not evident from the steady-state perturbation. However, the dynamic response profile and kinetics of cerebrovascular function have not been determined to date. We tested the hypotheses that bilateral middle cerebral artery blood flow mean velocity (MCA) increases exponentially following the onset of moderate-intensity exercise in 10 healthy young subjects. The MCA response profiles were well fit to a delay (TD) + exponential (time constant, τ) model with substantial agreement for baseline [left (L): 69, right (R): 64 cm/s, coefficient of variation (CV) 11%], response amplitude (L: 16, R: 13 cm/s, CV 23%), TD (L: 54, R: 52 s, CV 9%), τ (L: 30, R: 30 s, CV 22%), and mean response time (MRT) (L: 83, R: 82 s, CV 8%) between left and right MCA as supported by the high correlations (e.g., MRT = 0.82, < 0.05) and low CVs. Test-retest reliability was high with CVs for the baseline, amplitude, and MRT of 3, 14, and 12%, respectively. These responses contrasted markedly with those of three healthy older subjects in whom the MCA baseline and exercise response amplitude were far lower and the kinetics slowed. A single older stroke patient showed baseline ipsilateral MCA that was lower still and devoid of any exercise response whatsoever. We conclude that kinetics analysis of MCA during exercise has significant potential to unveil novel aspects of cerebrovascular function in health and disease. Resolution of the dynamic stimulus-response profile provides a greater understanding of the underlying the physiological control processes than steady-state measurements alone. We report a novel method of measuring cerebrovascular blood velocity (MCAv) kinetics under ecologically valid conditions from rest to moderate-intensity exercise. This technique reveals that brain blood flow increases exponentially following the onset of exercise with ) a strong bilateral coherence in young healthy individuals, and ) a potential for unique age- and disease-specific profiles.
对运动等刺激的动态反应能够揭示健康和疾病状态下系统控制方面的宝贵见解，而这些见解在稳态扰动中并不明显。然而，迄今为止，脑血管功能的动态反应特征和动力学尚未确定。我们对10名健康年轻受试者进行了测试，以验证以下假设：在中等强度运动开始后，双侧大脑中动脉血流平均速度（MCA）呈指数增加。MCA反应特征与延迟（TD）+指数（时间常数，τ）模型拟合良好，在基线方面有高度一致性[左侧（L）：69，右侧（R）：64 cm/s，变异系数（CV）11%]，反应幅度（L：16，R：13 cm/s，CV 23%），TD（L：54，R：52 s，CV 9%），τ（L：30，R：30 s，CV 22%），以及左右MCA之间的平均反应时间（MRT）（L：83，R：82 s，CV 8%），高相关性（例如，MRT = 0.82，<0.05）和低CV值支持了这一点。重测信度较高，基线、幅度和MRT的CV值分别为3%、14%和12%。这些反应与三名健康老年受试者形成了显著对比，他们的MCA基线和运动反应幅度要低得多，动力学也较慢。一名老年中风患者的同侧MCA基线更低，且完全没有任何运动反应。我们得出结论，运动期间MCA的动力学分析在揭示健康和疾病状态下脑血管功能的新方面具有巨大潜力。与单独的稳态测量相比，动态刺激-反应特征的解析能更深入地理解潜在的生理控制过程。我们报告了一种在符合生态学效度的条件下，从静息状态到中等强度运动测量脑血管血流速度（MCAv）动力学的新方法。该技术表明，运动开始后脑血流量呈指数增加，在年轻健康个体中具有很强的双侧一致性，并且具有独特年龄和疾病特异性特征的潜力。
