Aging, muscle fiber type, and contractile function in sprint-trained athletes

• Published in: Journal of applied physiology (1985) Vol. 101; no. 3; pp. 906 - 917
• Main Authors: Korhonen, Marko T, Cristea, Alexander, Alen, Markku, Hakkinen, Keijo, Sipila, Sarianna, Mero, Antti, Viitasalo, Jukka T, Larsson, Lars, Suominen, Harri
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.09.2006; American Physiological Society
• Subjects: Adaptation, Physiological - physiology; Adolescent; Adult; Age Factors; Aged; Aged, 80 and over; Aging; Aging - pathology; Aging - physiology; Athletes; Biological and medical sciences; Exercise; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Male; MEDICIN; MEDICINE; Middle Aged; Muscle Fibers, Fast-Twitch - cytology; Muscle Fibers, Fast-Twitch - physiology; muscle strength; Muscle, Skeletal - cytology; Muscle, Skeletal - physiology; Muscular system; myosin heavy chain; Proteins; Running - physiology; single-fiber contractile properties; Physical exercise; Human; myosin heavy chain; Heavy peptide chain; Senescence; single-fiber contractile properties; Ageing; exercise; Muscular fiber; Striated muscle; Athlete; Running locomotion; muscle strength; Sport; Vertebrata; Mammalia; Myosin
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.00299.2006

1 Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland; 2 Department of Clinical Neurophysiology, University of Uppsala, Uppsala, Sweden; 3 Department of Biology of Physical Activity, University of Jyväskylä; 4 The Finnish Centre for Interdisciplinary Gerontology; 5 KIHU — Research Institute for Olympic Sports, Jyväskylä, Finland Submitted 10 March 2006 ; accepted in final form 9 May 2006 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. exercise; myosin heavy chain; single-fiber contractile properties; muscle strength Address for reprint requests and other correspondence: H. Suominen, Dept. of Health Sciences, Univ. of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland (e-mail: harri.suominen{at}sport.jyu.fi )