急性常压缺氧会导致转矩-频率关系右移,但对激活后电位没有影响。

IF 3.3 3区 医学 Q1 PHYSIOLOGY
Journal of applied physiology Pub Date : 2024-11-01 Epub Date: 2024-09-19 DOI:10.1152/japplphysiol.00378.2024
Christina D Bruce, Mathew I B Debenham, Brian H Dalton, Chris J McNeil
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引用次数: 0

摘要

低吸入氧分压(FIO2;即缺氧)会影响人体骨骼肌收缩力的各个方面,但目前仍不清楚激活后电位(PAP)和扭矩-频率(T-F)关系是否会发生改变。我们研究了两小时(H2)和四小时(H4)的常压低氧(FIO2=0.11±0.47)分别对 13 名和 12 名健康参与者膝关节伸肌(KE)的 PAP 值和背屈肌(DF)的 T-F 关系的影响。为了评估膝关节伸展肌张力,在10秒最大自主收缩(MVC)之前和之后的2-300秒,通过刺激股神经诱发静止抽搐。通过单脉冲刺激腓总神经和 5-100 Hz 之间的 1 秒列车获得 T-F 关系。缺氧时,外周血氧饱和度从基线时的 98.0±0.8% 下降了约 18% (P
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Acute normobaric hypoxia causes a rightward shift in the torque-frequency relationship but has no effect on postactivation potentiation.

Low fractions of inspired oxygen ([Formula: see text]; i.e., hypoxia) affect aspects of skeletal muscle contractility in humans, but it remains unclear if postactivation potentiation (PAP) and the torque-frequency (T-F) relationship are altered. We investigated the effects of 2 (H2) and 4 (H4) h of normobaric hypoxia ([Formula: see text] = 0.11 ± 0.47) on the magnitude of PAP of the knee extensors and the T-F relationship of the dorsiflexors in 13 and 12 healthy participants, respectively. To assess PAP, a resting twitch was evoked via femoral nerve stimulation before and 2-300 s after a 10-s maximal voluntary contraction (MVC). A T-F relationship was obtained by stimulating the common fibular nerve with a single pulse and 1-s trains between 5 and 100 Hz. During hypoxia, peripheral oxygen saturation decreased by ∼18% from 98.0 ± 0.8% at baseline (P < 0.001). MVC force and voluntary activation (VA) of the knee extensors were lower than baseline throughout hypoxia (e.g., ∼8% and ∼5%, respectively, at H2; P ≤ 0.027); however, the magnitude of PAP was not altered by hypoxia (P ≥ 0.711). Surprisingly, PAP did increase with time across the control day (P ≤ 0.012). MVC torque and VA of the dorsiflexors were unaffected by hypoxia (P ≥ 0.127), but the estimated frequency required to evoke 50% of 100 Hz torque increased by ∼1.2 Hz at H2 (P ≤ 0.021). These results imply that 2 h of normobaric hypoxia were sufficient to 1) impair neural drive to the knee extensors but not the mechanism(s) responsible for PAP and 2) lead to a rightward shift of the T-F relationship for the dorsiflexors.NEW & NOTEWORTHY Postactivation potentiation of the knee extensors was unaffected by 4 h of normobaric hypoxia exposure but may be confounded by hypoxia-related impairments to the conditioning contraction. In the dorsiflexors, contractile rates increased in hypoxia, which led to a rightward shift of the torque-frequency relationship, such that a higher frequency was required to obtain 50% of maximal torque. These results expand our understanding of the acute effects of hypoxia on skeletal muscle function.

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来源期刊
CiteScore
6.00
自引率
9.10%
发文量
296
审稿时长
2-4 weeks
期刊介绍: The Journal of Applied Physiology publishes the highest quality original research and reviews that examine novel adaptive and integrative physiological mechanisms in humans and animals that advance the field. The journal encourages the submission of manuscripts that examine the acute and adaptive responses of various organs, tissues, cells and/or molecular pathways to environmental, physiological and/or pathophysiological stressors. As an applied physiology journal, topics of interest are not limited to a particular organ system. The journal, therefore, considers a wide array of integrative and translational research topics examining the mechanisms involved in disease processes and mitigation strategies, as well as the promotion of health and well-being throughout the lifespan. Priority is given to manuscripts that provide mechanistic insight deemed to exert an impact on the field.
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