Distribution of different fiber types in human skeletal muscles: Effects of aging studied in whole muscle cross sections

Abstract

The effects of aging on the total number and size of fibers, and the proportion and distribution of type 1 (slow twitch) and type 2 (fast twitch) fibers were studied in cross sections (15 mu thick) of autopsied whole m. vastus lateralis from two age groups. Each group consisted of six, previously physically healthy males (mean age 72 +/- 1 years and 30 +/- 6 years, respectively). The size of the muscles of the older individuals was 18% smaller (P less than 0.01) and the total number of fibers was 25% lower (P less than 0.01) than those of the young individuals (mean number 364,000 +/- 50,000 vs 478,000 +/- 56,000). There was, however, no significant difference in the mean fiber size (indirectly determined) or the proportion of the two fiber types, though a preferential reduction in type 2 fiber number in the aged individuals was seen. The relative occurrence of the fiber types at various depths in the aged muscles was found to be more even than in muscles from the young individuals. The results suggest that the aging atrophy in m. vastus lateralis, at least up to the age of 70, is primarily the result of a loss of fibers.

Age-related differences in fat-free mass, skeletal muscle, body cell mass and fat mass between 18 and 94 years

“…Baumgartner et al (1995) suggested that the active cell mass may be replaced to a greater extent in women than in men, but had no explanation for this apparent sex difference. Lexell et al (1983) found 18% smaller muscle size and 25% fewer number of muscle cells at autopsy in elderly men (70 ± 73 y) than in young men (19 ± 37 y), which is close to the 16% lower ASMM and 25% lower BCM noted in this study. Thus sarcopenia in elderly subjects may be due to muscle atrophy due to a gradual and selective loss of cell mass, and a decrease in number and size of muscle ®bres (Lexell et al, 1995).…”

Elevated SOCS3 and altered IL-6 signaling is associated with age-related human muscle stem cell dysfunction

“…It is clear from several previous studies that there is a preferential loss of type II fibers and reduction in type II fiber CSA with age (31,59). Furthermore, recent data using fiber type-specific immunofluorescent microscopy demonstrate that in addition to a preferential loss of type II fiber CSA there is a type II specific loss of SCs per myofiber in older muscle (37,59).…”

Genes and the ageing muscle: a review on genetic association studies

“…appendicular mass relative to height 2 that is ≤7.23 kg m −2 in men and ≤5.67 kg m −2 in women) and a gait speed of less than 1 m s −1 (Fielding et al 2011). On a myocellular level, sarcopenia is characterized by a reduction in muscle fibre number as well as fibre size, with specific type II muscle fibre atrophy (Lexell et al 1983(Lexell et al , 1988. Muscle mass usually reaches its peak at the age of 25-30 years and thereafter begins to decline (Lexell et al 1988;Janssen et al 2000).…”