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Human single muscle fibre function with 84 day bed-rest and resistance exercise.
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2004 (English)In: Journal of physiology, ISSN 0022-3751, Vol. 557, 501-513 p.Article in journal (Refereed) Published
Abstract [en]

Muscle biopsies were obtained from the vastus lateralis before and after 84 days of bed-rest fromsix control (BR) and six resistance-exercised (BRE) men to examine slow- and fast-twitch muscle fibre contractile function. BR did not exercise during bed-rest and had a 17 and 40% decrease inwholemuscle size and function, respectively. TheBREgroup performedfour sets of seven maximal concentric and eccentric supine squats 2–3 days perweek (every third day) that maintained whole muscle strength and size. Slow (MHC I) and fast (MHC IIa) muscle fibres were studied at 15◦C for diameter, peak force (Po), contractile velocity (Vo) and force–power parameters. SDS-PAGE was performed on each single fibre after the functional experiments to determine MHC isoform composition. MHCI and IIa BR fibres were, respectively, 15 and 8% smaller, 46 and 25% weaker (Po), 21 and 6% slower (Vo), and 54 and 24% less powerful after bed-rest (P<0.05). BR MHCI and IIa Po and power normalized to cell size were lower (P<0.05). BRE MHCI fibres showed no change in size or Vo after bed-rest; however, Po was 19%lower (P<0.05), resulting in 20 and30%declines (P<0.05) in normalizedPo and power, respectively. BREMHCIIa fibres showed no change in size, Po and power after bed-rest, while Vo waselevated13%(P<0.05).BREMHCIIanormalizedPo andpowerwere10and15%lower (P<0.05), respectively.MHCisoformcomposition shifted away fromMHCI fibres, resulting in an increase (P<0.05) inMHCI/IIa (BR and BRE) andMHCIIa/IIx (BR only) fibres. These data show that the contractile function of the MHCI fibres was more affected by bed-rest and less influenced by the resistance exercise protocol than the MHCIIa fibres. Considering the large differences inpower ofhumanMHCIandIIamusclefibres (5- to6-fold), the maintenance of wholemuscle function with the resistance exercise programme is probably explained by (1) the maintenance of MHCIIa power and (2) the shift from slow to fast (MHC I→MHCI/IIa) in

Place, publisher, year, edition, pages
2004. Vol. 557, 501-513 p.
Keyword [en]
atrophy, muscle size, skeletal muscle, flywheel resistance exercise
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:miun:diva-4510DOI: 10.1113/jphysiol.2004.062166Local ID: 5864OAI: oai:DiVA.org:miun-4510DiVA: diva2:29542
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2011-01-10Bibliographically approved

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CiteExportLink to record
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Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
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More styles
Language
  • de-DE
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  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
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  • Other locale
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Output format
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  • asciidoc
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