title: Morphologic differences in skeletal muscle with age in normally active human males and their well-trained counterparts.
abstract: In this study we elucidate the interaction of physical activity with aging as regards skeletal muscle fiber distribution and size. Thirty-three male athletes and 42 normally active counterparts served as subjects. They were assigned to younger (less than 25.5 years) and older (greater than 25.5 years) subgroups. Serial cross-sections from muscle biopsy samples (musculus vastus lateralis) were stained to distinguish fiber type: fast glycolytic (type IIb), fast oxidative-glycolytic (type IIa), or slow oxidative (type I). We also measured fiber diameters. A greater mean diameter of type I fibers was seen in older as opposed to younger athletes. Older controls had a smaller mean diameter of type IIb fibers than did younger controls. Athletes had a smaller mean percentage of type IIa fibers and a greater mean percentage of type I fibers than did controls. There was a greater mean percentage of type I fibers in older as opposed to younger controls, but this was not the case in athletes. Athletes may have larger fibers and a greater percentage of type I fibers at the expense of type IIa fibers. Atrophy of fibers with aging might be retarded by training, which might also reduce the age-associated rate of type IIb percentage loss and type I percentage gain.
authors.affiliation: Department of Physiology, Faculty of Physical Education and Sport, Charles University, Prague, Czechoslovakia.
authors.forename: J
authors.initials: J
authors.lastname: Melichna
authors.forename: C W
authors.initials: CW
authors.lastname: Zauner
authors.forename: L
authors.initials: L
authors.lastname: Havlícková
authors.forename: J
authors.initials: J
authors.lastname: Novák
authors.forename: D W
authors.initials: DW
authors.lastname: Hill
authors.forename: R J
authors.initials: RJ
authors.lastname: Colman
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D006801:Humans; D008297:Male; D009132:Muscles / Q000033:anatomy & histology* / Q000502:physiology; D010806:Physical Education and Training; D012016:Reference Values