Christina D Bruce, Mathew I B Debenham, Brian H Dalton, Chris J McNeil
{"title":"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。","authors":"Christina D Bruce, Mathew I B Debenham, Brian H Dalton, Chris J McNeil","doi":"10.1152/japplphysiol.00378.2024","DOIUrl":null,"url":null,"abstract":"<p><p>Low fractions of inspired oxygen (FI<sub>O2</sub>; i.e., hypoxia) affect aspects of skeletal muscle contractility in humans, but it remains unclear if post-activation potentiation (PAP) and the torque-frequency (T-F) relationship are altered. We investigated the effects of two (H2) and four hours (H4) of normobaric hypoxia (FI<sub>O2</sub>=0.11±0.47) on the magnitude of PAP of the knee extensors (KE) and the T-F relationship of the dorsiflexors (DF) in 13 and 12 healthy participants, respectively. To assess PAP, a resting twitch was evoked via femoral nerve stimulation before, and 2-300 s following 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 5-100 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 KE 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 DF 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 two hours of normobaric hypoxia were sufficient to: i) impair neural drive to the KE but not the mechanism(s) responsible for PAP, and ii) lead to a rightward shift of the T-F relationship for the DF.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":null,"pages":null},"PeriodicalIF":3.3000,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Acute normobaric hypoxia causes a rightward shift in the torque-frequency relationship, but has no effect on post-activation potentiation.\",\"authors\":\"Christina D Bruce, Mathew I B Debenham, Brian H Dalton, Chris J McNeil\",\"doi\":\"10.1152/japplphysiol.00378.2024\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>Low fractions of inspired oxygen (FI<sub>O2</sub>; i.e., hypoxia) affect aspects of skeletal muscle contractility in humans, but it remains unclear if post-activation potentiation (PAP) and the torque-frequency (T-F) relationship are altered. We investigated the effects of two (H2) and four hours (H4) of normobaric hypoxia (FI<sub>O2</sub>=0.11±0.47) on the magnitude of PAP of the knee extensors (KE) and the T-F relationship of the dorsiflexors (DF) in 13 and 12 healthy participants, respectively. To assess PAP, a resting twitch was evoked via femoral nerve stimulation before, and 2-300 s following 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 5-100 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 KE 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 DF 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 two hours of normobaric hypoxia were sufficient to: i) impair neural drive to the KE but not the mechanism(s) responsible for PAP, and ii) lead to a rightward shift of the T-F relationship for the DF.</p>\",\"PeriodicalId\":15160,\"journal\":{\"name\":\"Journal of applied physiology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.3000,\"publicationDate\":\"2024-09-19\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of applied physiology\",\"FirstCategoryId\":\"3\",\"ListUrlMain\":\"https://doi.org/10.1152/japplphysiol.00378.2024\",\"RegionNum\":3,\"RegionCategory\":\"医学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"PHYSIOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of applied physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1152/japplphysiol.00378.2024","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"PHYSIOLOGY","Score":null,"Total":0}
Acute normobaric hypoxia causes a rightward shift in the torque-frequency relationship, but has no effect on post-activation potentiation.
Low fractions of inspired oxygen (FIO2; i.e., hypoxia) affect aspects of skeletal muscle contractility in humans, but it remains unclear if post-activation potentiation (PAP) and the torque-frequency (T-F) relationship are altered. We investigated the effects of two (H2) and four hours (H4) of normobaric hypoxia (FIO2=0.11±0.47) on the magnitude of PAP of the knee extensors (KE) and the T-F relationship of the dorsiflexors (DF) in 13 and 12 healthy participants, respectively. To assess PAP, a resting twitch was evoked via femoral nerve stimulation before, and 2-300 s following 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 5-100 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 KE 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 DF 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 two hours of normobaric hypoxia were sufficient to: i) impair neural drive to the KE but not the mechanism(s) responsible for PAP, and ii) lead to a rightward shift of the T-F relationship for the DF.
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.