title: The specific force of single intact extensor digitorum longus and soleus mouse muscle fibers declines with aging.
abstract: In the present study we measured, for the first time, the isometric specific force (SF, force normalized to cross sectional area) generated by single intact fibers from fast- (extensor digitorum longus, EDL) and slow-twitch (soleus) muscles from young adult (2-6), middle-aged (12-14) and old (20-24 month-old) mice. SF has also been measured in single intact flexor digitorum brevis fibers from young mice. Muscle fibers have been classified into fast- or slow-twitch based on the contraction kinetics. Maximum SF recorded in EDL and soleus fibers from young and middle-aged mice did not differ significantly. A significant age-dependent decline in maximum SF was recorded in EDL and soleus fibers from young or middle-aged to old mice. The SF was 377 +/- 18, 417 +/- 20 and 279 +/- 18 kPa for EDL fibers from young, middle-aged and old mice, respectively and 397 +/- 17, 405 +/- 24 and 320 +/- 33 kPa for soleus fibers from age-matched mice, respectively. The frequency needed to elicit maximum force in EDL and soleus fibers from middle-aged to old mice did not differ significantly. In conclusion, the specific force developed by both fast and slow-twitch single intact muscle fibers declines with aging and more significantly in the former.
authors.affiliation: Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
authors.forename: E
authors.initials: E
authors.lastname: González
authors.forename: M L
authors.initials: ML
authors.lastname: Messi
authors.forename: O
authors.initials: O
authors.lastname: Delbono
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D005260:Female; D007537:Isometric Contraction; D007700:Kinetics; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D009119:Muscle Contraction; D024510:Muscle Development; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000502:physiology*; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000502:physiology; D018995:Myosin Heavy Chains / Q000032:analysis; D020033:Protein Isoforms / Q000032:analysis; D013047:Specific Pathogen-Free Organisms
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains