Oxygen availability and PCr recovery rate in untrained human calf muscle: evidence of metabolic limitation in normoxia

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Title Oxygen availability and PCr recovery rate in untrained human calf muscle: evidence of metabolic limitation in normoxia
Author Haseler, Luke Jonathon; Lin, Alexander; Hoff, Jan; Richardson, Russell S.
Journal Name American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
Editor Curt D. Sigmund
Year Published 2007
Place of publication Bethesda, MD, USA
Publisher The American Physiological Society
Abstract In contrast to their exercise-trained counterparts, the maximal oxidative rate of skeletal muscle in sedentary humans appears not to benefit from supplemental O2 availability but is impacted by severe hypoxia, suggesting a metabolic limitation either at or below ambient O2 levels. However, the critical level of O2 availability at which maximal metabolic rate is reduced in sedentary humans is unknown. Using 31P magnetic resonance spectroscopy and arterial oximetry, phosphocreatine (PCr) recovery kinetics and arterial oxygenation were assessed in six sedentary subjects performing 5-min bouts of plantar flexion exercise followed by 6 min of recovery. Each trial was repeated while breathing one of four different fractions of inspired O2 (FIO2) (0.10, 0.12, 0.15, and 0.21). The PCr recovery rate constant (a marker of oxidative capacity) was unaffected by reductions in FIO2, remaining at a value of 1.5 ± 0.2 min−1 until arterial O2 saturation (SaO2) fell to less than ∼92%, the average value reached breathing an FIO2 of 0.15. Below this SaO2, the PCr rate constant fell significantly by 13 and 31% to 1.3 ± 0.2 and 1.0 ± 0.2 min−1 (P < 0.05) as SaO2 was reduced to 82 ± 3 and 77 ± 2%, respectively. In conclusion, this study has revealed that O2 availability does not impact maximal oxidative rate in sedentary humans until the O2 level falls well below that of ambient air, indicating a metabolic limitation in normoxia.
Peer Reviewed Yes
Published Yes
Alternative URI http://dx.doi.org/10.1152/ajpregu.00039.2007
Copyright Statement Self-archiving of the author-manuscript version is not yet supported by this journal. Please refer to the journal link for access to the definitive, published version or contact the author[s] for more information.
Volume 293
Page from R2046
Page to R2051
ISSN 0363-6119
Date Accessioned 2008-02-25
Date Available 2015-02-05T03:44:10Z
Language en_US
Research Centre Griffith Health Institute; Heart Foundation Research Centre
Faculty Griffith Health Faculty
Subject PRE2009-Physiology
URI http://hdl.handle.net/10072/17913
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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