Aging, muscle fiber type, and contractile function in sprint-trained athletes
2006 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 101, no 3, 906-917 p.Article in journal (Refereed) Published
Biopsy samples were taken from the vastus lateralis of 18- to 84-yr-old male sprinters (n = 91). Fiber-type distribution, cross-sectional area, and myosin heavy chain (MHC) isoform content were identified using ATPase histochemistry and SDS-PAGE. Specific tension and maximum shortening velocity (V-o) were determined in 144 single skinned fibers from younger (18-33 yr, n = 8) and older (53-77 yr, n = 9) runners. Force-time characteristics of the knee extensors were determined by using isometric contraction. The cross-sectional area of type I fibers was unchanged with age, whereas that of type II fibers was reduced (P < 0.001). With age there was an increased MHC I (P < 0.01) and reduced MHC IIx isoform content (P < 0.05) but no differences in MHC IIa. Specific tension of type I and IIa MHC fibers did not differ between younger and older subjects. V-o of fibers expressing type I MHC was lower (P < 0.05) in older than in younger subjects, but there was no difference in V-o of type IIa MHC fibers. An aging-related decline of maximal isometric force (P < 0.001) and normalized rate of force development (P < 0.05) of knee extensors was observed. Normalized rate of force development was positively associated with MHC II (P < 0.05). The sprint-trained athletes experienced the typical aging-related reduction in the size of fast fibers, a shift toward a slower MHC isoform profile, and a lower V-o of type I MHC fibers, which played a role in the decline in explosive force production. However, the muscle characteristics were preserved at a high level in the oldest runners, underlining the favorable impact of sprint exercise on aging muscle.
Place, publisher, year, edition, pages
2006. Vol. 101, no 3, 906-917 p.
exercise, myosin heavy chain, single-fiber contractile properties, muscle strength
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-97418DOI: 10.1152/japplphysiol.00299.2006ISI: 000240124100031PubMedID: 16690791OAI: oai:DiVA.org:uu-97418DiVA: diva2:172362