title: Effects of ageing and gender on contractile properties in human skeletal muscle and single fibres.
abstract: OBJECTIVE
  The objective of this study is to improve our understanding of the mechanisms underlying the ageing- and gender-related muscle weakness.
  
  
  METHODS
  Ageing- and gender-related differences in regulation of muscle contraction have been studied in knee-extensor muscles at the whole muscle and single muscle fibre levels in young and old sedentary men and women. In vivo knee-extensor muscle function was measured at slow (30 degrees s(-1)) and faster (180 degrees s(-1)) speeds of movement. Maximum velocity of unloaded shortening (V(0)) and maximum force normalized to cross-sectional area (CSA) [specific tension (ST)] were measured in single 'skinned' skeletal muscle fibre segments.
  
  
  RESULTS
  Significant ageing- and gender-related differences were observed in muscle torque. A 33-55% ageing-related decline (P < 0.001) in maximum torque was observed irrespective of gender. At the single muscle fibre level, the ageing-related decline in knee-extensor muscle function was accompanied by a 20-28% decline in ST in muscle fibres expressing the type I MyHC isoform in both men and women, and a 29% decline in type IIa muscle fibre CSA, but the decreased fast-twitch fibre size was restricted to the men. Furthermore, in both men and women, V(0) decreased in muscle cells expressing the type I and IIa MyHC isoforms.
  
  
  CONCLUSIONS
  The present results provide evidence of specific ageing- and gender-related differences in regulation of muscle contraction at the cellular level. It is suggested that these cellular changes have a significant impact on muscle function and the ageing-related motor handicap.
authors.affiliation: Center for Development and Health Genetics, Pennsylvania State University, University Park, PA, USA.
authors.forename: F
authors.initials: F
authors.lastname: Yu
authors.forename: M
authors.initials: M
authors.lastname: Hedström
authors.forename: A
authors.initials: A
authors.lastname: Cristea
authors.forename: N
authors.initials: N
authors.lastname: Dalén
authors.forename: L
authors.initials: L
authors.lastname: Larsson
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000502:physiology*; D012727:Sex Characteristics
chemical_list: D009124:Muscle Proteins