Improved single muscle fiber quality in the oldest-old

J Appl Physiol (1985). 2016 Oct 1;121(4):878-884. doi: 10.1152/japplphysiol.00479.2016. Epub 2016 Aug 11.

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.

Keywords: aging; contractile function; muscle quality; oldest-old; single fiber.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Aged, 80 and over
  • Aging / physiology*
  • Female
  • Humans
  • Male
  • Muscle Contraction / physiology*
  • Muscle Fibers, Skeletal / physiology*
  • Muscle Strength / physiology*
  • Quadriceps Muscle / physiology*