Improved single muscle fiber quality in the oldest-old

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 hea...

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Bibliographic Details
Published in:Journal of applied physiology (1985) 2016-10, Vol.121 (4), p.878-884
Main Authors: Grosicki, Greg J, Standley, Robert A, Murach, Kevin A, Raue, Ulrika, Minchev, Kiril, Coen, Paul M, Newman, Anne B, Cummings, Steven, Harris, Tamara, Kritchevsky, Stephen, Goodpaster, Bret H, Trappe, Scott
Format: Article
Language:English
Subjects:
Aged, 80 and over
Aging - physiology
Female
Humans
Male
Muscle Contraction - physiology
Muscle Fibers, Skeletal - physiology
Muscle Strength - physiology
Muscular system
Oldest old people
Power
Proteins
Quadriceps Muscle - physiology
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Summary: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 μm ; n = 58) was 21% larger (P < 0.05) than MHC IIa fibers (4,518 ± 386 μm ; 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.
ISSN:8750-7587
1522-1601
DOI:10.1152/japplphysiol.00479.2016