title: Reduction in single muscle fiber rate of force development with aging is not attenuated in world class older masters athletes.
abstract: Normal adult aging is associated with impaired muscle contractile function; however, to what extent cross-bridge kinetics are altered in aging muscle is not clear. We used a slacken restretch maneuver on single muscle fiber segments biopsied from the vastus lateralis of young adults (∼23 yr), older nonathlete (NA) adults (∼80 yr), and age-matched world class masters athletes (MA; ∼80 yr) to assess the rate of force redevelopment (ktr) and cross-bridge kinetics. A post hoc analysis was performed, and only the mechanical properties of "slow type" fibers based on unloaded shortening velocity (Vo) measurements are reported. The MA and NA were ∼54 and 43% weaker, respectively, for specific force compared with young. Similarly, when force was normalized to cross-sectional area determined via the fiber shape angularity data, both old groups did not differ, and the MA and NA were ∼43 and 48% weaker, respectively, compared with young (P < 0.05). Vo for both MA and NA old groups was 62 and 46% slower, respectively, compared with young. Both MA and NA adults had approximately two times slower values for ktr compared with young. The slower Vo in both old groups relative to young, coupled with a similarly reduced ktr, suggests impaired cross-bridge kinetics are responsible for impaired single fiber contractile properties with aging. These results challenge the widely accepted resilience of slow type fibers to cellular aging.
authors.affiliation: Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada; Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Calgary, Alberta, Canada; gapower@uoguelph.ca.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Power
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada; The Muscle Physiology and Biophysics Laboratory, McGill University, Montreal, Quebec, Canada;
authors.forename: Fábio C
authors.initials: FC
authors.lastname: Minozzo
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada;
authors.forename: Sally
authors.initials: S
authors.lastname: Spendiff
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada;
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Filion
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada;
authors.forename: Yana
authors.initials: Y
authors.lastname: Konokhova
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada;
authors.forename: Maddy F
authors.initials: MF
authors.lastname: Purves-Smith
authors.affiliation: Département de Kinanthropologie, Université du Québec a' Montréal, Montreal, Quebec, Canada;
authors.forename: Charlotte
authors.initials: C
authors.lastname: Pion
authors.affiliation: Département de Kinanthropologie, Université du Québec a' Montréal, Montreal, Quebec, Canada;
authors.forename: Mylène
authors.initials: M
authors.lastname: Aubertin-Leheudre
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada;
authors.forename: José A
authors.initials: JA
authors.lastname: Morais
authors.affiliation: Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Calgary, Alberta, Canada;
authors.forename: Walter
authors.initials: W
authors.lastname: Herzog
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada; Meakins Christie Laboratories, McGill University, Montreal, Quebec, Canada; and.
authors.forename: Russell T
authors.initials: RT
authors.lastname: Hepple
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada;
authors.forename: Tanja
authors.initials: T
authors.lastname: Taivassalo
authors.affiliation: Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada; The Muscle Physiology and Biophysics Laboratory, McGill University, Montreal, Quebec, Canada; Meakins Christie Laboratories, McGill University, Montreal, Quebec, Canada; and Department of Physics, McGill University, Montreal, Quebec, Canada.
authors.forename: Dilson E
authors.initials: DE
authors.lastname: Rassier
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D056352:Athletes; D001706:Biopsy; D005455:Fluorescent Antibody Technique; D006801:Humans; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000737:chemistry; D053580:Muscle Strength; D018995:Myosin Heavy Chains / Q000032:analysis; D052097:Quadriceps Muscle / Q000737:chemistry / Q000503:physiopathology*; D055948:Sarcopenia / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D018995:Myosin Heavy Chains
keywords: aging; muscle; sarcopenia; velocity; weakness