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Reduced muscle oxidative capacity is independent of O(2) availability in elderly people.
MedLine Citation:
PMID:  22760857     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Impaired O(2) transport to skeletal muscle potentially contributes to the decline in aerobic capacity with aging. Thus, we examined whether (1) skeletal muscle oxidative capacity decreases with age and (2) O(2) availability or mitochondrial capacity limits the maximal rate of mitochondrial ATP synthesis in vivo in sedentary elderly individuals. We used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine the PCr recovery kinetics in six young (26 ± 10 years) and six older (69 ± 3 years) sedentary subjects following 4 min of dynamic plantar flexion exercise under different fractions of inspired O(2) (FiO(2), normoxia 0.2; hyperoxia 1.0). End-exercise pH was not significantly different between old (7.04 ± 0.10) and young (7.05 ± 0.04) and was not affected by breathing hyperoxia (old 7.08 ± 0.08, P > 0.05 and young 7.05 ± 0.03). Likewise, end-exercise PCr was not significantly different between old (19 ± 4 mM) and young (24 ± 5 mM) and was not changed in hyperoxia. The PCr recovery time constant was significantly longer in the old (36 ± 9 s) compared to the young in normoxia (23 ± 8 s, P < 0.05) and was not significantly altered by breathing hyperoxia in both the old (35 ± 9 s) and young (29 ± 10 s) groups. Therefore, this study reveals that the muscle oxidative capacity of both sedentary young and old individuals is independent of O(2) availability and that the decline in oxidative capacity with age is most likely due to limited mitochondrial content and/or mitochondrial dysfunction and not O(2) availability.
Authors:
Gwenael Layec; Luke J Haseler; Russell S Richardson
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-4
Journal Detail:
Title:  Age (Dordrecht, Netherlands)     Volume:  -     ISSN:  1574-4647     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101250497     Medline TA:  Age (Dordr)     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, USA, gwenael.layec@utah.edu.
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