Research Institute of Physical Fitness, Japan Women's College of Physical Education, Kita-Karasuyama, Setagaya-ku, Tokyo 157-8565, Japan.
J Physiol. 2011 Jun 1;589(Pt 11):2847-56. doi: 10.1113/jphysiol.2010.204461. Epub 2011 Mar 28.
The mechanism underlying the plateau or relative decrease in cerebral blood flow (CBF) during maximal incremental dynamic exercise remains unclear. We hypothesized that cerebral perfusion is limited during high-intensity dynamic exercise due to a redistribution of carotid artery blood flow. To identify the distribution of blood flow among the arteries supplying the head and brain, we evaluated common carotid artery (CCA), internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA) blood flow during dynamic exercise using Doppler ultrasound. Ten subjects performed graded cycling exercise in a semi-supine position at 40, 60 and 80% of peak oxygen uptake (VO2 peak) for 5 min at each workload. The ICA blood flow increased by 23.0 ± 4.6% (mean ± SE) from rest to exercise at 60% (VO2 peak). However, at 80% (VO2 peak), ICA blood flow returned towards near resting levels (9.6 ± 4.7% vs. rest). In contrast, ECA, CCA and VA blood flow increased proportionally with workload. The change in ICA blood flow during graded exercise was correlated with end-tidal partial pressure of CO2 (r = 0.72). The change in ICA blood flow from 60% (VO2 peak) to 80% (VO2 peak) was negatively correlated with the change in ECA blood flow (r = −0.77). Moreover, there was a significant correlation between forehead cutaneous vascular conductance and ECA blood flow during exercise (r = 0.79). These results suggest that during high-intensity dynamic exercise the plateau or decrease in ICA blood flow is partly due to a large increase in ECA blood flow, which is selectively increased to prioritize thermoregulation.
在最大递增动态运动期间，脑血流（CBF）的高原或相对减少的机制尚不清楚。我们假设由于颈动脉血流的再分配，大脑灌注在高强度动态运动期间受到限制。为了确定供应头部和大脑的动脉之间的血流分布，我们使用多普勒超声评估了动态运动期间颈总动脉（CCA）、颈内动脉（ICA）、颈外动脉（ECA）和椎动脉（VA）的血流。10 名受试者以半仰卧位进行分级循环运动，在 40%、60%和 80%的峰值摄氧量（VO2 peak）下，每个工作量持续 5 分钟。与休息时相比，在 60%（VO2 peak）时，ICA 血流增加了 23.0±4.6%（平均值±SE）。然而，在 80%（VO2 peak）时，ICA 血流接近休息水平（9.6±4.7%比休息时）。相比之下，ECA、CCA 和 VA 血流与工作量成比例增加。在分级运动期间，ICA 血流的变化与潮气末二氧化碳分压（r=0.72）相关。从 60%（VO2 peak）到 80%（VO2 peak）时，ICA 血流的变化与 ECA 血流的变化呈负相关（r=-0.77）。此外，运动期间额部皮肤血管导纳与 ECA 血流之间存在显著相关性（r=0.79）。这些结果表明，在高强度动态运动期间，ICA 血流的高原或减少部分是由于 ECA 血流的大量增加所致，ECA 血流选择性增加以优先进行体温调节。
