title: Improved single muscle fiber quality in the oldest-old.
abstract: We examined single muscle fiber contractile function of the oldest-old (3F/2M, 89 ± 1 yr old) enrolled in The Health, Aging, and Body Composition Study (The Health ABC Study). Vastus lateralis muscle biopsies were obtained and single muscle fiber function was determined (n = 105) prior to myosin heavy chain (MHC) isoform identification with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cross-sectional area of MHC I muscle fibers (5,576 ± 333 μm2; n = 58) was 21% larger (P < 0.05) than MHC IIa fibers (4,518 ± 386 μm2; n = 47). Normalized power (an indicator of muscle fiber quality incorporating size, strength, and speed) of MHC I and IIa muscle fibers was 2.3 ± 0.1 and 17.4 ± 0.8 W/l, respectively. Compared with previous research from our lab using identical procedures, MHC I normalized power was 28% higher than healthy 20 yr olds and similar to younger octogenarians (∼80 yr old). Normalized power of MHC IIa fibers was 63% greater than 20 yr olds and 39% greater than younger octogenarians. These comparative data suggest that power output per unit size (i.e., muscle quality) of remaining muscle fibers improves with age, a phenomenon more pronounced in MHC IIa fibers. Age-related single muscle fiber quality improvements may be a compensatory mechanism to help offset decrements in whole muscle function.
authors: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors: Greg J
authors: GJ
authors: Grosicki
authors: Translational Research Institute for Metabolism and Diabetes, Orlando, Florida.
authors: Robert A
authors: RA
authors: Standley
authors: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors: Kevin A
authors: KA
authors: Murach
authors: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors: Ulrika
authors: U
authors: Raue
authors: Human Performance Laboratory, Ball State University, Muncie, Indiana.
authors: Kiril
authors: K
authors: Minchev
authors: Translational Research Institute for Metabolism and Diabetes, Orlando, Florida.
authors: Paul M
authors: PM
authors: Coen
authors: Center for Aging and Population Health, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors: Anne B
authors: AB
authors: Newman
authors: California Pacific Medical Center Research Institute, San Francisco, California.
authors: Steven
authors: S
authors: Cummings
authors: Laboratory of Epidemiology and Population Sciences, National Institute on Aging, Bethesda, Maryland; and.
authors: Tamara
authors: T
authors: Harris
authors: Sticht Center on Aging, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors: Stephen
authors: S
authors: Kritchevsky
authors: Translational Research Institute for Metabolism and Diabetes, Orlando, Florida.
authors: Bret H
authors: BH
authors: Goodpaster
authors: Human Performance Laboratory, Ball State University, Muncie, Indiana; strappe@bsu.edu.
authors: Scott
authors: S
authors: Trappe
mesh_terms: D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*
keywords: aging; contractile function; muscle quality; oldest-old; single fiber