Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan.
Research Center for Total Life Health and Sports Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan.
PLoS One. 2020 Apr 21;15(4):e0231643. doi: 10.1371/journal.pone.0231643. eCollection 2020.
Low-intensity training involving high repetitions is recommended to enhance muscular endurance. Hyperoxic conditions could increase the number of repetitions until exhaustion and thereby improve the results of muscular endurance training. This study aimed to investigate the acute effects of hyperoxia on dynamic muscular endurance, and determine individual factors that may be related to these effects. A single-blinded, counterbalanced crossover design was used. Twenty-five young men performed repetitions of the one-arm preacher curl at 30% of their 1-repetition maximum until exhaustion under hyperoxic and normoxic conditions. The maximum number of repetitions was recorded as an index of muscular endurance. Electromyogram (EMG) and near-infrared spectroscopy parameters were measured in the biceps brachii. The maximum number of repetitions was greater (P < 0.001) under hyperoxic conditions (132 ± 59 repetitions) than under normoxic conditions (114 ± 40 repetitions). The root mean square amplitude of EMG and oxygenated hemoglobin concentration for the last five repetitions under normoxic conditions were greater than those under hyperoxic conditions (P = 0.015 and P = 0.003, respectively). The percent change in the maximum number of repetitions between hyperoxic and normoxic conditions had significant positive correlations with individual maximal oxygen uptake measured using an incremental cycle ergometer test (r = 0.562, 95% confidence intervals [CI] = 0.213-0.783, P = 0.003), but not with muscle strength (τ = -0.124, 95% CI = -0.424-0.170, P = 0.387). The 95% CI for the correlation coefficient between the percent change in the maximum number of repetitions and muscular endurance included 0 (τ = 0.284, 95% CI = -0.003-0.565, P = 0.047); this indicated no significant correlation between the two parameters. The results suggest that hyperoxia can acutely enhance dynamic muscular endurance, with delayed elevation of EMG amplitude due to fatigue, and the effects are associated with individual whole-body endurance capacity.
低强度、高重复次数的训练被推荐用于增强肌肉耐力。高氧环境可以增加直至力竭的重复次数，从而改善肌肉耐力训练的效果。本研究旨在探讨高氧对动态肌肉耐力的急性影响，并确定可能与这些影响相关的个体因素。采用单盲、交叉平衡设计。25 名年轻男性在高氧和常氧条件下，以 1 次重复最大力量的 30%进行单臂牧师弯举，直至力竭，记录最大重复次数作为肌肉耐力的指标。肱二头肌的肌电图（EMG）和近红外光谱参数进行了测量。高氧条件下（132 ± 59 次）的最大重复次数明显高于常氧条件下（114 ± 40 次）（P < 0.001）。常氧条件下最后 5 次重复的 EMG 均方根振幅和氧合血红蛋白浓度大于高氧条件（P = 0.015 和 P = 0.003）。高氧和常氧条件下最大重复次数的百分比变化与递增式测功计试验测量的个体最大摄氧量呈显著正相关（r = 0.562，95%置信区间 [CI] = 0.213-0.783，P = 0.003），但与肌肉力量无关（τ = -0.124，95%CI = -0.424-0.170，P = 0.387）。最大重复次数百分比变化与肌肉耐力之间的相关系数的 95%CI 不包括 0（τ = 0.284，95%CI = -0.003-0.565，P = 0.047）；这表明这两个参数之间没有显著的相关性。结果表明，高氧可急性增强动态肌肉耐力，由于疲劳导致 EMG 振幅延迟升高，而这种影响与个体全身耐力能力有关。
