Table1_Impact of systemic hypoxia and blood flow restriction on mechanical, cardiorespiratory, and neuromuscular responses to a multiple-set repeated sprint exercise.docx

Introduction: Repeated sprint cycling exercises (RSE) performed under systemic normobaric hypoxia (HYP) or with blood flow restriction (BFR) are of growing interest. To the best of our knowledge, there is no stringent consensus on the cardiorespiratory and neuromuscular responses between systemic HYP and BFR during RSE. Thus, this study assessed cardiorespiratory and neuromuscular responses to multiple sets of RSE under HYP or with BFR.
Methods: According to a crossover design, fifteen men completed RSE (three sets of five 10-s sprints with 20 s of recovery) in normoxia (NOR), HYP, and with bilaterally-cuffed BFR at 45% of resting arterial occlusive pressure during sets in NOR. Power output, cardiorespiratory and neuromuscular responses were assessed.
Results: Average peak and mean powers were lower in BFR (dz = 0.87 and dz = 1.23, respectively) and HYP (dz = 0.65 and dz = 1.21, respectively) compared to NOR (p < 0.001). The percentage decrement of power output was greater in BFR (dz = 0.94) and HYP (dz = 0.64) compared to NOR (p < 0.001), as well as in BFR compared to NOR (p = 0.037, dz = 0.30). The percentage decrease of maximal voluntary contraction of the knee extensors after the session was greater in BFR compared to NOR and HYP (p = 0.011, dz = 0.78 and p = 0.027, dz = 0.75, respectively). Accumulated ventilation during exercise was higher in HYP and lower in BFR (p = 0.002, dz = 0.51, and p < 0.001, dz = 0.71, respectively). Peak oxygen consumption was reduced in HYP (p < 0.001, dz = 1.47). Heart rate was lower in BFR during exercise and recovery (p < 0.001, dz = 0.82 and p = 0.012, dz = 0.43, respectively). Finally, aerobic contribution was reduced in HYP compared to NOR (p = 0.002, dz = 0.46) and BFR (p = 0.005, dz = 0.33).
Discussion: Thus, this study indicates that power output during RSE is impaired in HYP and BFR and that BFR amplifies neuromuscular fatigue. In contrast, HYP did not impair neuromuscular function but enhanced the ventilatory response along with reduced oxygen consumption.

引言：在常压低氧环境（systemic normobaric hypoxia, HYP）下或采用血流限制（blood flow restriction, BFR）手段进行的重复冲刺骑行练习（Repeated Sprint Cycling Exercises，以下简称RSE）正受到越来越多的关注。据我们所知，目前尚无针对RSE过程中常压低氧与血流限制二者对心肺及神经肌肉反应的严格共识。因此，本研究旨在评估常压低氧或血流限制条件下，多组RSE对应的心肺与神经肌肉反应变化。
研究方法：本研究采用交叉设计，招募15名男性受试者，分别在常氧环境（normoxia, NOR）、常压低氧环境，以及常氧组训练期间采用双侧袖带式血流限制（压力设置为静息动脉闭塞压的45%）三种条件下完成RSE（3组练习，每组含5次10秒冲刺，组间休息20秒）。本研究对受试者的功率输出、心肺及神经肌肉反应进行了评估。
研究结果：与常氧组相比，血流限制组（dz分别为0.87和1.23）与常压低氧组（dz分别为0.65和1.21）的平均峰值功率与平均功率均更低（p < 0.001）。功率输出的下降百分比在血流限制组（dz=0.94）与常压低氧组（dz=0.64）中均高于常氧组（p < 0.001），且血流限制组高于常氧组（p=0.037, dz=0.30）。训练后膝伸肌最大自主收缩量的下降百分比，血流限制组显著高于常氧组与常压低氧组（分别为p=0.011, dz=0.78；p=0.027, dz=0.75）。运动期间的累积通气量在常压低氧组更高、血流限制组更低（分别为p=0.002, dz=0.51；p < 0.001, dz=0.71）。常压低氧组的峰值摄氧量有所降低（p < 0.001, dz=1.47）。运动过程与恢复期内，血流限制组的心率均更低（分别为p < 0.001, dz=0.82；p=0.012, dz=0.43）。最后，与常氧组和血流限制组相比，常压低氧组的有氧供能占比均有所降低（分别为p=0.002, dz=0.46；p=0.005, dz=0.33）。
讨论：综上，本研究表明，常压低氧与血流限制均会降低RSE过程中的功率输出，且血流限制会加剧神经肌肉疲劳。与之相反，常压低氧并未损害神经肌肉功能，但可提升通气反应并降低摄氧量。