title: Shared genetic and environmental effects on strength and power in older female twins.
abstract: OBJECTIVE
  This study examined the relative contribution of genetic and environmental effects on maximal leg extensor power and also investigated whether leg extensor power and maximum voluntary isometric knee extensor strength share a genetic component.
  
  
  METHODS
  Muscle functions were measured as part of the Finnish Twin Study on Aging in 101 monozygotic (MZ) and 116 dizygotic (DZ) female twin pairs aged 63-76 yr. Leg extensor power was measured using the Nottingham Leg Extensor Power Rig and maximum voluntary isometric knee extensor strength using an adjustable dynamometer chair. The analyses were carried out using the maximum likelihood method in Mx-program on the raw data set.
  
  
  RESULTS
  A bivariate Cholesky decomposition model showed that leg extensor power and isometric knee extensor strength shared a genetic component in common, which accounted for 32% of the total variance in leg extensor power and 48% in isometric knee extensor strength. In addition, power and strength had a nonshared environmental effect in common accounting for four percent of the variance in power and 52% in strength. Remaining variance for leg extensor power was due to trait-specific shared and nonshared environmental effects.
  
  
  CONCLUSIONS
  Observed genetic effect in common for leg extensor power and maximum voluntary isometric knee extensor strength indicated that these two traits are regulated by the same genes. However, also environmental effects have a significant role in explaining the variability in power and strength.
authors.affiliation: The Finnish Centre for Interdisciplinary Gerontology, Department of Health Sciences, University of Jyväskylä, P.O. Box 35(Viveca), Fin-40014 University of Jyväskylä, Finland. tiainen@sport.jyu.fi
authors.forename: Kristina
authors.initials: K
authors.lastname: Tiainen
authors.forename: Sarianna
authors.initials: S
authors.lastname: Sipilä
authors.forename: Markku
authors.initials: M
authors.lastname: Alén
authors.forename: Eino
authors.initials: E
authors.lastname: Heikkinen
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.forename: Asko
authors.initials: A
authors.lastname: Tolvanen
authors.forename: Satu
authors.initials: S
authors.lastname: Pajala
authors.forename: Taina
authors.initials: T
authors.lastname: Rantanen
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015444:Exercise / Q000502:physiology; D005260:Female; D005387:Finland; D006801:Humans; D007717:Knee / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology; D008875:Middle Aged; D009132:Muscles / Q000502:physiology*; D014427:Twins / Q000502:physiology*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic