Age-associated changes in the mechanical properties of human cadaveric pelvic floor muscles

Lindsey A. Burnett, Mark Cook, Sameer Shah, Ms Michelle Wong, Deborah M. Kado, Marianna Alperin

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Proper function of the female pelvic floor requires intact pelvic floor muscles (PFMs). The prevalence of pelvic floor disorders (PFDs) increases substantially with age, in part due to clinically identified deterioration of PFM function with age. However, the etiology of this decline remains largely unknown. We previously demonstrated that PFMs undergo age-related fibrotic changes. This study sought to determine whether aging also impacts PFMs’ passive mechanical properties that are largely determined by the intramuscular extracellular matrix. Biopsies from younger (≤52y) and older (>52y) female cadaveric donors were procured from PFMs, specifically coccygeus (C) and two portions of the levator ani - iliococcygeus (IC) and pubovisceralis (PV), and the appendicular muscles - obturator internus (OI) and vastus lateralis (VL). Muscle bundles were subjected to a passive loading protocol, and stress-sarcomere length (Ls) relationships calculated. Muscle stiffness was compared between groups using 2-way ANOVA and Sidak pairwise comparisons, α < 0.05. The mean age was 43.4 ± 11.6y and 74.9 ± 11.9y in younger (N = 5) and older (N = 10) donors, respectively. In all PFMs, the quadratic coefficient of parabolic regression of the stress-Ls curve, a measure of stiffness, was lower in the younger versus older group: C: 33.7 ± 13.9 vs 87.2 ± 10.7, P = 0.02; IC: 38.3 ± 12.7 vs 84.5 ± 13.9, P = 0.04; PV: 24.7 ± 8.8 vs 74.6 ± 9.6, P = 0.04. In contrast, non-PFM stiffness was not affected by aging: OI: 14.5 ± 4.7 vs 32.9 ± 6.2, P = 0.8 and VL: 13.6 ± 5.7 vs 30.1 ± 5.3, P = 0.9. Age-associated increase in PFM stiffness is predicted to negatively impact PFM function by diminishing muscle load-bearing, excursional, contractile, and regenerative capacity, thus predisposing older women to PFDs.

Original languageEnglish (US)
Article number109436
JournalJournal of Biomechanics
Volume98
DOIs
StatePublished - Jan 2 2020

Bibliographical note

Funding Information:
This research was supported by the National Institute of Health/National Institute of Aging grant ( R03AG050951 ) and National Institute of Health/National Institute of Child Health and Human Development (K12HD001259) awarded to Marianna Alperin, MD MS. Sponsors were not involved in the study design, collection, analysis, interpretation of the data, in writing the manuscript, or the decision to submit the manuscript for publication.

Funding Information:
The authors thank the individuals who donated their bodies to the University of Minnesota's Anatomy Bequest Program for the advancement of education and research. This research was supported by the National Institute of Health/National Institute of Aging grant (R03AG050951) and National Institute of Health/National Institute of Child Health and Human Development (K12HD001259) awarded to Marianna Alperin, MD MS. Sponsors were not involved in the study design, collection, analysis, interpretation of the data, in writing the manuscript, or the decision to submit the manuscript for publication.

Keywords

  • Aging
  • Passive mechanics
  • Pelvic floor disorders
  • Pelvic floor muscles
  • Stiffness

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural

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