Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom.
Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Australia.
J Appl Physiol (1985). 2022 Jul 1;133(1):214-222. doi: 10.1152/japplphysiol.00862.2021. Epub 2022 Jun 16.
The aim of this study was to compare the kinetic response of middle cerebral artery blood velocity (MCAv) to moderate- and heavy-intensity cycling in adults, and explore the relationship between maximal oxygen uptake (V̇o) and MCAv kinetics. Seventeen healthy adults (23.8 ± 2.4 yr, 9 females) completed a ramp incremental test to exhaustion on a cycle ergometer to determine V̇o and the gas exchange threshold (GET). Across six separate visits, participants completed three 6-min transitions at a moderate intensity (90% GET) and three at a heavy intensity (40% of the difference between GET and V̇o). Bilateral MCAv was measured using transcranial Doppler (TCD) ultrasonography and analyzed using a monoexponential model with a time delay. The time constant (τ) of the MCAv response was not different between moderate- and heavy-intensity cycling (25 ± 10 vs. 26 ± 8 s, = 0.82), as was the time delay (29 ± 11 vs. 29 ± 10 s, = 0.95). The amplitude of the exponential increase in MCAv from baseline was greater during heavy-intensity cycling (23.9 ± 10.0 cm·s, 34.1 ± 14.4%) compared with moderate-intensity cycling (12.7 ± 4.4 cm·s, 18.7 ± 7.5%; < 0.01). Following the exponential increase, a greater fall in MCAv was observed during heavy-intensity exercise compared with moderate-intensity exercise (9.5 ± 6.9 vs. 2.8 ± 3.8 cm·s, < 0.01). MCAv after 6 min of exercise remained elevated during heavy-intensity exercise compared with moderate-intensity exercise (85.2 ± 9.6 vs. 79.3 ± 7.7 cm·s, ≤ 0.01). V̇o was not correlated with MCAv τ or amplitude ( = 0.11-0.26, > 0.05). These data suggest that the intensity of constant-work rate exercise influences the amplitude, but not time-based, response parameters of MCAv in healthy adults, and found no relationship between cardiorespiratory fitness and MCAv kinetics. This is the first study to model the MCAv kinetic response to moderate- and heavy-intensity cycling in healthy adults. This study found that the amplitude of the exponential rise in MCAv at exercise onset was greater during heavy-intensity exercise (∼34%) compared with moderate-intensity exercise (∼19%), but the time-based characteristics of the responses were similar between intensities. Higher cardiorespiratory fitness was not associated with a greater or faster MCAv response to moderate- or heavy-intensity exercise.
本研究旨在比较成年人中等强度和高强度踏车运动时大脑中动脉血流速度（MCAv）的动力学反应，并探讨最大摄氧量（V̇o）与 MCAv 动力学之间的关系。17 名健康成年人（23.8±2.4 岁，9 名女性）在功率自行车上进行递增至力竭的斜坡递增试验，以确定 V̇o 和气体交换阈值（GET）。在六次单独的访问中，参与者以中等强度（90%GET）和高强度（GET 和 V̇o 之间的差值的 40%）各完成三次 6 分钟的过渡。使用经颅多普勒（TCD）超声测量双侧 MCAv，并使用具有时间延迟的单指数模型进行分析。MCAv 反应的时间常数（τ）在中等强度和高强度踏车运动之间没有差异（25±10 与 26±8 s， = 0.82），时间延迟也没有差异（29±11 与 29±10 s， = 0.95）。与中等强度运动（12.7±4.4 cm·s，18.7±7.5%）相比，高强度运动时 MCAv 从基线呈指数增加的幅度更大（23.9±10.0 cm·s，34.1±14.4%； < 0.01）。与中等强度运动相比，高强度运动后观察到 MCAv 更大的下降（9.5±6.9 与 2.8±3.8 cm·s， < 0.01）。与中等强度运动相比，高强度运动 6 分钟后 MCAv 仍保持升高（85.2±9.6 与 79.3±7.7 cm·s， ≤ 0.01）。V̇o 与 MCAv τ 或幅度无相关性（ = 0.11-0.26， > 0.05）。这些数据表明，等功速运动的强度影响健康成年人 MCAv 的幅度，但不影响基于时间的反应参数，心肺功能与 MCAv 动力学之间无相关性。这是首次在健康成年人中对中等强度和高强度踏车运动的 MCAv 动力学反应进行建模的研究。本研究发现，高强度运动（34%）时 MCAv 指数上升的幅度大于中等强度运动（19%），但两种强度下的反应时间特征相似。较高的心肺功能与中等强度或高强度运动时 MCAv 反应的幅度或速度增加无关。
