Department of Kinesiology, Kansas State University, Manhattan, KS, USA.
Department of Kinesiology, Kansas State University, Manhattan, KS, USA.
Microvasc Res. 2020 Sep;131:104002. doi: 10.1016/j.mvr.2020.104002. Epub 2020 Mar 18.
This study compared the brachial artery blood flow (Q̇) and microvascular oxygen delivery responses during handgrip exercise above vs. below critical force (CF; the isometric analog of critical power). Q̇ and microvascular oxygen delivery are important determinants of oxygen utilization and metabolite accumulation during exercise, both of which increase progressively during exercise above CF. However the Q̇ and microvascular oxygen delivery responses above vs. below CF remain unknown. We hypothesized that Q̇, deoxygenated-heme (deoxy-[heme]; an estimate of microvascular fractional oxygen extraction), and total-heme concentrations (total-[heme]; an estimate of changes in microvascular hematocrit) would demonstrate physiological maximums above CF despite increases in exercise intensity. Seven men and six women performed 1) a 5-min rhythmic isometric-handgrip maximal-effort test (MET) to determine CF and 2) two constant target-force tests above (severe-intensity; S1 and S2) and two constant target-force tests below (heavy-intensity; H1 and H2) CF. CF was 189.3 ± 16.7 N (29.7 ± 1.6%MVC). At end-exercise, Q̇ was greater for tests above CF (S1: 418 ± 147 mL/min; S2: 403 ± 137 mL/min) compared to tests below CF (H1: 287 ± 97 mL/min; H2: 340 ± 116 mL/min; all p < 0.05) but was not different between S1 and S2. Further, end-test Q̇ during both tests above CF was not different from Q̇ estimated at CF (392 ± 37 mL/min). At end-exercise, deoxy-[heme] was not different between tests above CF (S1: 150 ± 50 μM; S2: 155 ± 57 μM), but was greater during tests above CF compared to tests below CF (H1: 101 ± 24 μM; H2: 111 ± 21 μM; all p < 0.05). At end-exercise, total-[heme] was not different between tests above CF (S1: 404 ± 58 μM; S2: 397 ± 73 μM), but was greater during tests above CF compared to H1 (352 ± 58 μM; p < 0.01) but not H2 (371 ± 57 μM). These data suggest limb blood flow limitations exist and maximal levels of muscle microvascular oxygen delivery and extraction occur during exercise above, but not below, CF.
本研究比较了握力运动时肱动脉血流量 (Q̇) 和微血管氧输送反应在临界力 (CF；临界功率的等长模拟) 以上和以下的情况。Q̇和微血管氧输送是运动期间氧利用和代谢物积累的重要决定因素，这两者在 CF 以上的运动中逐渐增加。然而，CF 以上和以下的 Q̇和微血管氧输送反应仍然未知。我们假设，尽管运动强度增加，但 Q̇、去氧血红素 (deoxy-[heme]；微血管局部氧提取的估计值) 和总血红素浓度 (total-[heme]；微血管血细胞比容变化的估计值) 将在 CF 以上显示出生理最大值。七名男性和六名女性进行了 1) 5 分钟节律性等长握力最大努力测试 (MET) 以确定 CF 和 2) 两个以上恒定目标力测试 (严重强度；S1 和 S2) 和两个以下恒定目标力测试 (重强度；H1 和 H2)。CF 为 189.3 ± 16.7 N(29.7 ± 1.6%MVC)。在运动结束时，CF 以上的测试 (S1: 418 ± 147 mL/min；S2: 403 ± 137 mL/min) 的 Q̇大于 CF 以下的测试 (H1: 287 ± 97 mL/min；H2: 340 ± 116 mL/min；所有 p < 0.05)，但 S1 和 S2 之间没有差异。此外，CF 以上的两项测试的终末测试 Q̇与 CF 时估计的 Q̇ (392 ± 37 mL/min) 没有差异。在运动结束时，CF 以上的测试之间的去氧 [heme] 没有差异 (S1: 150 ± 50 μM；S2: 155 ± 57 μM)，但 CF 以上的测试高于 CF 以下的测试 (H1: 101 ± 24 μM；H2: 111 ± 21 μM；所有 p < 0.05)。在运动结束时，CF 以上的测试之间的总 [heme] 没有差异 (S1: 404 ± 58 μM；S2: 397 ± 73 μM)，但 CF 以上的测试高于 H1 (352 ± 58 μM；p < 0.01)，但低于 H2 (371 ± 57 μM)。这些数据表明，肢体血流限制存在，最大的肌肉微血管氧输送和提取水平发生在 CF 以上的运动中，而不是 CF 以下的运动中。
