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<p>This study is the first to determine how hypoxia affects human muscle fatigue kinetics and metabolic perturbations during intense dynamic exercise. Using randomized, single-blinded crossover designs, three trials of two-legged knee extensions were performed under hypoxic (HYP, FiO₂ 0.135) and normoxic (NOR) conditions. Trial 1 (<i>n</i> = 8): quadriceps femoris twitch force (F<sub>tw</sub>) was measured before, during, and after 4&#xa0;min intense exercise followed by exhaustive exercise. Maximal voluntary contraction (MVC) was measured pre- and post-exercise. Trial 2 (<i>n</i> = 8): muscle lactate and pH were determined before and after 4&#xa0;min intense exercise. Trial 3 (<i>n</i> = 6): blood was sampled frequently from the femoral artery and vein during intense exhaustive exercise. Dynamic F<sub>tw</sub> decreased more (<i>P</i> &lt; 0.05) in HYP from 60s of exercise and onwards. After 4&#xa0;min, isometric F<sub>tw</sub> decreased more (<i>P</i> &lt; 0.05) in HYP, whereas MVC was similar between conditions. At exhaustion, isometric F<sub>tw</sub> and MVC were similar between conditions despite HYP exercise time being 55 ± 17% of NOR (<i>P</i> &lt; 0.01). Muscle lactate and pH in- and decreased more (<i>P</i> &lt; 0.001), respectively, after 4&#xa0;min in HYP. Exercise-induced blood metabolites disturbances were largely unaffected by hypoxia. Conclusively, moderate hypoxia accelerated muscular fatigue from 60s and onwards. Hypoxia caused higher muscle but not blood lactate and H<sup>+</sup> accumulation rates.</p>

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Time-course of muscle fatigue development during intense exercise in hypoxia and normoxia

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年4月23日

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  • Jacob Bejder,
  • Jonathan Graae,
  • Jakob Boye Andersen,
  • Ricardo Augusto Barbieri,
  • Eduardo Zapaterra Campos,
  • Jens Bangsbo,
  • Lars Nybo,
  • Nikolai Baastrup Nordsborg

摘要

This study is the first to determine how hypoxia affects human muscle fatigue kinetics and metabolic perturbations during intense dynamic exercise. Using randomized, single-blinded crossover designs, three trials of two-legged knee extensions were performed under hypoxic (HYP, FiO₂ 0.135) and normoxic (NOR) conditions. Trial 1 (n = 8): quadriceps femoris twitch force (Ftw) was measured before, during, and after 4 min intense exercise followed by exhaustive exercise. Maximal voluntary contraction (MVC) was measured pre- and post-exercise. Trial 2 (n = 8): muscle lactate and pH were determined before and after 4 min intense exercise. Trial 3 (n = 6): blood was sampled frequently from the femoral artery and vein during intense exhaustive exercise. Dynamic Ftw decreased more (P < 0.05) in HYP from 60s of exercise and onwards. After 4 min, isometric Ftw decreased more (P < 0.05) in HYP, whereas MVC was similar between conditions. At exhaustion, isometric Ftw and MVC were similar between conditions despite HYP exercise time being 55 ± 17% of NOR (P < 0.01). Muscle lactate and pH in- and decreased more (P < 0.001), respectively, after 4 min in HYP. Exercise-induced blood metabolites disturbances were largely unaffected by hypoxia. Conclusively, moderate hypoxia accelerated muscular fatigue from 60s and onwards. Hypoxia caused higher muscle but not blood lactate and H+ accumulation rates.