School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Perth, Australia.
Murdoch Applied Sports Science Laboratory, Murdoch University, Murdoch, Australia.
Eur J Sport Sci. 2023 Jul;23(7):1223-1232. doi: 10.1080/17461391.2022.2095929. Epub 2022 Jul 25.
This study examined whether hypoxia during multi-set, high-load resistance exercise alters neuromuscular responses. Using a single-blinded (participants), randomised crossover design, eight resistance-trained males completed five sets of five repetitions of bench press at 80% of one repetition maximum in moderate normobaric hypoxia (inspiratory oxygen fraction = 0.145) and normoxia. Maximal isometric bench press trials were performed following the warm-up, after 10 min of altitude priming and 5 min post-session (outside, inside and outside the chamber, respectively). Force during pre-/post-session maximal voluntary isometric contractions and bar velocity during exercise sets were measured along with surface electromyographic (EMG) activity of the pectoralis major, anterior deltoid and lateral and medial triceps muscles. Two-way repeated measures ANOVA (condition×time) were used. A significant time effect ( = 0.048) was found for mean bar velocity, independent of condition ( = 0.423). During sets of the bench press exercise, surface EMG amplitude of all studied muscles remained unchanged ( > 0.187). During maximal isometric trials, there were no main effects of condition ( > 0.666) or time ( > 0.119), nor were there any significant condition×time interactions for peak or mean forces and surface EMG amplitudes ( > 0.297). Lower end-exercise blood oxygen saturation (90.9 ± 1.8 vs. 98.6 ± 0.6%; < 0.001) and higher blood lactate concentration (5.8 ± 1.4 vs. 4.4 ± 1.6 mmol/L; = 0.007) values occurred in hypoxia. Acute delivery of systemic normobaric hypoxia during multi-set, high-load resistance exercise increased metabolic stress. However, only subtle neuromuscular function adjustments occurred with and without hypoxic exposure either during maximal isometric bench press trials before versus after the session or during actual exercise sets.Performing multi-set, high-load bench press resistance exercise in hypoxia accentuates metabolic stress, as evidenced by lower arterial oxygen saturation and higher blood lactate concentration, compared to normoxia.Acute hypoxic exposure doesn't alter neuromuscular responses during the execution of the sets since mean bar velocity dropped similarly in both conditions from set 2 to set 5 with no difference in peak velocity and surface EMG amplitude of the prime movers during the bench press.Only subtle adjustments in peak or mean force and accompanying surface EMG activity occur with and without hypoxic exposure during maximal isometric bench press trials after a 10-min hypoxic priming period and 5 min after the session in reference to post-warm-up.
这项研究旨在探讨多组、大负荷抗阻运动过程中的缺氧是否会改变神经肌肉反应。采用单盲（参与者）、随机交叉设计，8 名经过抗阻训练的男性在中度常压低氧（吸气氧分数=0.145）和常氧环境下完成 5 组 5 次卧推，每组重复 80%的 1 次最大重复次数。在热身结束后、高原预适应 10 分钟后和 5 分钟后（分别在室外、室内和室外）进行最大等长卧推试验。在试验前/后最大自主等长收缩期间测量力，以及在运动组期间测量棒速度，并测量胸大肌、前三角肌以及外侧和内侧肱三头肌的表面肌电图（EMG）活动。使用双因素重复测量方差分析（条件×时间）。发现平均棒速度存在显著的时间效应（ = 0.048），与条件无关（ = 0.423）。在卧推运动的组间，所有研究肌肉的表面 EMG 幅度保持不变（ > 0.187）。在最大等长试验中，条件没有主效应（ > 0.666）或时间（ > 0.119），峰值或平均力和表面 EMG 幅度也没有显著的条件×时间相互作用（ > 0.297）。在低氧条件下，运动结束时的血氧饱和度（90.9 ± 1.8 比 98.6 ± 0.6%； < 0.001）和血乳酸浓度（5.8 ± 1.4 比 4.4 ± 1.6 mmol/L； = 0.007）较低。多组、大负荷抗阻运动过程中系统常压低氧的急性输送增加了代谢应激。然而，在试验前后的最大等长卧推试验期间，或者在实际运动组期间，无论是有缺氧暴露还是没有缺氧暴露，神经肌肉功能仅出现细微调整。与常氧相比，在低氧环境下进行多组、大负荷卧推抗阻运动时，动脉血氧饱和度降低，血乳酸浓度升高，代谢应激加重。急性低氧暴露不会改变在完成多组大负荷卧推运动期间的神经肌肉反应，因为在第 2 组到第 5 组之间，两组的平均棒速度都相似下降，在卧推过程中主要运动肌的峰值速度和表面肌电图幅度没有差异。在 10 分钟的低氧预适应期和 5 分钟的试验后，与热身结束后相比，只有在最大等长卧推试验后，无论是否有低氧暴露，峰值或平均力以及伴随的表面肌电图活动都会出现细微调整。
