Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, CANADA.
Med Sci Sports Exerc. 2020 Jan;52(1):161-169. doi: 10.1249/MSS.0000000000002100.
We investigated the effect of high-altitude acclimatization on peripheral fatigue compared with sea level and acute hypoxia.
At sea level (350 m), acute hypoxia (environmental chamber), and chronic hypoxia (5050 m, 5-9 d) (partial pressure of inspired oxygen = 140, 74 and 76 mm Hg, respectively), 12 participants (11 in chronic hypoxia) had the quadriceps of their dominant leg fatigued by three bouts of 75 intermittent electrically evoked contractions (12 pulses at 15 Hz, 1.6 s between train onsets, and 15 s between bouts). The initial peak force was ~30% of maximal voluntary force. Recovery was assessed by single trains at 1, 2, and 3 min postprotocol. Tissue oxygenation of rectus femoris was recorded by near-infrared spectroscopy.
At the end of the fatigue protocol, the impairments of peak force and peak rates of force development and relaxation were greater (all P < 0.05) in acute hypoxia (51%, 53%, and 64%, respectively) than sea level (43%, 43%, and 52%) and chronic hypoxia (38%, 35%, and 48%). Peak force and rate of force development recovered faster (P < 0.05) in chronic hypoxia (pooled data for 1-3 min: ~84% and 74% baseline, respectively) compared with sea level (73% and 63% baseline) and acute hypoxia (~70% and 55% baseline). Tissue oxygenation did not differ among conditions for fatigue or recovery (P > 0.05).
Muscle adaptations occurring with chronic hypoxia, independent of other adaptations, positively influence muscle contractility during and after repeated contractions at high altitude.
我们研究了与海平面和急性缺氧相比，高海拔适应对周围疲劳的影响。
在海平面（350 米）、急性缺氧（环境室）和慢性缺氧（5050 米，5-9 天）（吸入氧分压分别为 140、74 和 76 毫米汞柱）下，12 名参与者（11 名在慢性缺氧中）让其优势腿的四头肌通过三回合 75 次间歇性电诱发收缩（12 次脉冲，15 赫兹，1.6 秒脉冲间隔，15 秒回合间隔）疲劳。初始峰值力约为最大自主力的 30%。恢复情况通过协议结束后 1、2 和 3 分钟的单刺激进行评估。股直肌的组织氧合通过近红外光谱进行记录。
在疲劳协议结束时，急性缺氧（分别为51%、53%和 64%）比海平面（分别为43%、43%和 52%）和慢性缺氧（分别为38%、35%和 48%）时峰值力和峰值力发展及松弛率的损伤更大（均 P < 0.05）。与海平面（分别为73%和 63%基线）和急性缺氧（分别为70%和 55%基线）相比，慢性缺氧（1-3 分钟的合并数据：分别为84%和 74%基线）中峰值力和力发展率恢复更快（P < 0.05）。在疲劳或恢复期间，组织氧合在不同条件之间没有差异（P > 0.05）。
与其他适应不同，慢性缺氧引起的肌肉适应在高海拔地区反复收缩期间和之后积极影响肌肉收缩能力。
