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The impact of life-long strength versus endurance training on muscle fiber morphology and phenotype composition in older men

2023; American Physiological Society; Volume: 135; Issue: 6 Linguagem: Inglês

10.1152/japplphysiol.00208.2023

8750-7587

Tiril Tøien, Jakob Lindberg Nielsen, Ole Kristian Berg, Mathias Forsberg Brobakken, Stian Kwak Nyberg, Lars Espedal, Thomas Malmo, Ulrik Frandsen, Per Aagaard, Eivind Wang,

Body Composition Measurement Techniques

Aging is typically associated with decreased muscle strength and rate of force development (RFD), partly explained by motor unit remodeling due to denervation, and subsequent loss of fast-twitch type II myofibers. Exercise is commonly advocated to counteract this detrimental loss. However, it is unclear how life-long strength versus endurance training may differentially affect markers of denervation and reinnervation of skeletal myofibers and, in turn, affect the proportion and morphology of fast-twitch type II musculature. Thus, we compared fiber type distribution, fiber type grouping, and the prevalence of atrophic myofibers (≤1,494 µm