Department of Kinesiology, School of Public Health-Bloomington, Indiana University, Bloomington, IN.
Department of Anesthesiology, Mayo Clinic, Rochester, MN.
Med Sci Sports Exerc. 2019 May;51(5):900-911. doi: 10.1249/MSS.0000000000001882.
Ischemic preconditioning (IPC) before exercise has been shown to be a novel approach to improve performance in different exercise modes in normoxia (NORM). Few studies have been conducted examining potential mechanisms behind these improvements, and less has been done examining its influence during exercise in hypoxia (HYP). Oxygen uptake and extraction kinetics are factors that have been implicated as possible determinants of cycling performance. We hypothesized that IPC would lead to improvements in oxygen extraction and peripheral blood flow kinetics, and this would translate to improvements in cycling time trial (TT) performance in both NORM and HYP.
Thirteen men (age, 24 ± 7 yr; V˙O2max, 63.1 ± 5.1 mL·kg·min) participated in the study. Subjects completed trials of each combination of normobaric HYP (FiO2 = 0.16, simulating ~8000 ft/2500 m) or NORM (FiO2 = 0.21) with preexercise IPC protocol (4 × 5 min at 220 mm Hg) or SHAM procedure. Trials included submaximal constant load cycle exercise bouts (power outputs of 15% below gas exchange threshold, and 85% of V˙O2max), and a 5-km cycling performance TT.
Ischemic preconditioning significantly improved 5-km TT time in NORM by 0.9% ± 1.8% compared with SHAM (IPC, 491.2 ± 35.2 s vs SHAM, 495.9 ± 36.0 s; P < 0.05). Ischemic preconditioning did not alter 5-km TT performance times in HYP (P = 0.231). Ischemic preconditioning did, however, improve tissue oxygen extraction in HYP (deoxygenated hemoglobin/myoglobin: IPC, 21.23 ± 10.95 μM; SHAM, 19.93 ± 9.91 μM; P < 0.05) during moderate-intensity exercise.
Our data confirm that IPC is an effective ergogenic aid for athletes performing 5-km cycling TT bouts in NORM. Ischemic preconditioning did mitigate the declines in tissue oxygen during moderate-intensity exercise in HYP, but this did not translate to a significant effect on mean group performance. These data suggest that IPC may be of benefit for athletes training and competing in NORM.
在常氧（NORM）条件下进行的缺血预处理（IPC）已被证明是一种提高不同运动模式下表现的新方法。很少有研究探讨这些改善背后的潜在机制，而在低氧（HYP）条件下进行运动时，对其影响的研究则更少。氧摄取和提取动力学是被认为可能决定自行车运动表现的因素。我们假设 IPC 将导致氧提取和外周血流动力学的改善，这将转化为 NORM 和 HYP 中自行车计时赛（TT）表现的改善。
13 名男性（年龄，24 ± 7 岁；最大摄氧量，63.1 ± 5.1 mL·kg·min）参加了这项研究。受试者完成了常氧（FiO2 = 0.16，模拟~8000 英尺/2500 米）或 NORM（FiO2 = 0.21）与预运动 IPC 方案（4×5 分钟，220 mmHg）或 SHAM 程序的每种组合的试验。试验包括亚最大恒负荷自行车运动回合（功率输出低于气体交换阈值的 15%，和 85%的最大摄氧量）和 5 公里自行车 TT 性能。
与 SHAM 相比，IPC 显著提高了 NORM 中 5 公里 TT 时间 0.9%±1.8%（IPC，491.2±35.2 s 与 SHAM，495.9±36.0 s；P<0.05）。IPC 并未改变 HYP 中 5 公里 TT 性能时间（P=0.231）。然而，IPC 确实提高了 HYP 中组织氧提取（去氧血红蛋白/肌红蛋白：IPC，21.23±10.95 μM；SHAM，19.93±9.91 μM；P<0.05）在中等强度运动时。
我们的数据证实，IPC 是一种有效的运动促进剂，可用于在 NORM 中进行 5 公里自行车 TT 比赛的运动员。IPC 确实减轻了 HYP 中中等强度运动时组织氧的下降，但这并没有转化为对平均组表现的显著影响。这些数据表明，IPC 可能对在 NORM 中训练和比赛的运动员有益。
