Longitudinal decline of lower extremity muscle power in healthy and mobility-limited older adults: Influence of muscle mass, strength, composition, neuromuscular activation and single fiber contractile properties

Kieran F. Reid, Evan Pasha, Gheorghe Doros, David J. Clark, Carolynn Patten, Edward M. Phillips, Walter R. Frontera, Roger A. Fielding

Research output: Contribution to journalArticle

75 Scopus citations

Abstract

Purpose: This longitudinal study examined the major physiological mechanisms that determine the age-related loss of lower extremity muscle power in two distinct groups of older humans. We hypothesized that after ~3 years of follow-up, mobility-limited older adults (mean age: 77.2 ± 4, n = 22, 12 females) would have significantly greater reductions in leg extensor muscle power compared to healthy older adults (74.1 ± 4, n = 26, 12 females). Methods: Mid-thigh muscle size and composition were assessed using computed tomography. Neuromuscular activation was quantified using surface electromyography and vastus lateralis single muscle fibers were studied to evaluate intrinsic muscle contractile properties. Results: At follow-up, the overall magnitude of muscle power loss was similar between groups: mobility-limited: -8.5 % vs. healthy older: -8.8 %, P > 0.8. Mobility-limited elders had significant reductions in muscle size (-3.8 %, P < 0.01) and strength (-5.9 %, P < 0.02), however, these parameters were preserved in healthy older (P ≥ 0.7). Neuromuscular activation declined significantly within healthy older, but not in mobility-limited participants. Within both groups, the cross-sectional areas of type I and IIA muscle fibers were preserved while substantial increases in single fiber peak force (>30 %), peak power (>200 %) and unloaded shortening velocity (>50 %) were elicited at follow-up. Conclusion: Different physiological mechanisms contribute to the loss of lower extremity muscle power in healthy older and mobility-limited older adults. Neuromuscular changes may be the critical early determinant of muscle power deficits with aging. In response to major whole muscle decrements, major compensatory mechanisms occur within the contractile properties of surviving single muscle fibers in an attempt to restore overall muscle power and function with advancing age.

Original languageEnglish (US)
Pages (from-to)29-39
Number of pages11
JournalEuropean Journal of Applied Physiology
Volume114
Issue number1
DOIs
StatePublished - Jan 1 2014
Externally publishedYes

Keywords

  • Aging
  • Longitudinal
  • Lower extremity muscle power
  • Single muscle fiber

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)

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