title: Effects of strength and endurance training on muscle fibre characteristics in elderly women.
abstract: The effects of 18 weeks' intensive strength and endurance training on fibre characteristics of the vastus lateralis muscle were studied in 76- to 78-year-old women. Type I and type IIa fibres constituted over 90% of the cell population and were almost equally represented. No changes were observed in the proportions of the different fibre types. When comparing the baseline and the 18-week measurements within the groups, the strength group showed a mean increase of 34% (P = 0.028) in mean type I fibre area. The frequency histograms showed an increased proportion of larger type I fibres after strength training and a decreased proportion of smaller type IIa fibres after endurance training. In the control subjects, the proportion of smaller type I and type IIa fibres increased during the experimental period. The results indicate that intensive strength training induces type I fibre hypertrophy, whereas the effects of endurance training are less evident. The considerable variation found in the change in muscle fibre cross-sectional areas is also noteworthy.
authors.affiliation: Department of Health Sciences, University of Jyväskylä, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Sipilä
authors.forename: M
authors.initials: M
authors.lastname: Elorinne
authors.forename: M
authors.initials: M
authors.lastname: Alen
authors.forename: H
authors.initials: H
authors.lastname: Suominen
authors.forename: V
authors.initials: V
authors.lastname: Kovanen
mesh_terms: D000368:Aged; D000375:Aging / Q000473:pathology / Q000502:physiology; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D006984:Hypertrophy; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000502:physiology; D009133:Muscular Atrophy / Q000209:etiology / Q000473:pathology / Q000628:therapy; D010807:Physical Endurance / Q000502:physiology*