Document Detail

Skeletal muscle adaptations to prolonged exposure to extreme altitude: a role of physical activity?
MedLine Citation:
PMID:  19115916     Owner:  NLM     Status:  MEDLINE    
This study investigated skeletal muscle adaptations to high altitude and a possible role of physical activity levels. Biopsies were obtained from the m. quadriceps femoris (vastus) and m. biceps brachii (biceps) in 15 male subjects, 7 active and 8 less active. Samples were obtained at sea level and after 75 days altitude exposure at 5250 m or higher. The muscle fiber size decreased at an average of 15% in the vastus and biceps, respectively, and to the same extent in both groups. In both muscles, the mean number of capillaries was 2.1-2.2 cap.fiber(-1) before and after the exposure. As mean fiber area was reduced, the mean number of capillaries per unit area increased in all subjects (from 320 to 405 cap/mm2) with no difference between the active and less active groups. The two enzymes selected to reflect mitochondrial capacity, citrate synthase (CS) and 3-hydroxyl-CoA-dehydrogenase (HAD), did not change in the leg muscles with altitude exposure, CS: 28.7 (20.7-37.8) vs. 27.8 (23.8-29.4); HAD: 35.2 (20.3-43.1) vs. 30.6 (20.7-39.7) micromol.min(-1).g(-1) d.w, pre- and post-altitude, respectively. The muscle buffer capacity was elevated in both the vastus; 220 (194-240) vs. 232 (200-277) and the biceps muscles; 233 (190-301) vs. 253 (193-320) after the acclimatization period. In conclusion, mean fiber area was reduced in response to altitude exposure regardless of physical activity which in turn meant that with an unaltered capillary to fiber ratio there was an elevation in capillaries per unit of muscle area. Muscle enzyme activity was unaffected with altitude exposure in both groups, whereas muscle buffer capacity was increased.
Masao Mizuno; Gabrielle K Savard; Nils-Holger Areskog; Carsten Lundby; Bengt Saltin
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  High altitude medicine & biology     Volume:  9     ISSN:  1527-0297     ISO Abbreviation:  High Alt. Med. Biol.     Publication Date:  2008  
Date Detail:
Created Date:  2008-12-31     Completed Date:  2009-04-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901183     Medline TA:  High Alt Med Biol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  311-7     Citation Subset:  IM; S    
The Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark.
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MeSH Terms
3-Hydroxyacyl CoA Dehydrogenases / metabolism
Acclimatization / physiology*
Capillaries / physiology
Citrate (si)-Synthase / metabolism
Environmental Monitoring*
Middle Aged
Mitochondria, Muscle / enzymology*
Muscle, Skeletal / enzymology,  metabolism*,  pathology
Physical Endurance / physiology*
Reg. No./Substance:
EC CoA Dehydrogenases; EC (si)-Synthase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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