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 journalArticle

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

Fingerprint

Pelvic Floor
Muscle
Muscles
Mechanical properties
Pelvic Floor Disorders
Stiffness
Quadriceps Muscle
Bearings (structural)
Aging of materials
Tissue Donors
Sarcomeres
Biopsy
Weight-Bearing
Anal Canal
Analysis of variance (ANOVA)
Extracellular Matrix
Deterioration
Analysis of Variance

Keywords

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

PubMed: MeSH publication types

  • Journal Article

Cite this

Age-associated changes in the mechanical properties of human cadaveric pelvic floor muscles. / Burnett, Lindsey A.; Cook, Mark; Shah, Sameer; Michelle Wong, Ms; Kado, Deborah M.; Alperin, Marianna.

In: Journal of Biomechanics, Vol. 98, 109436, 02.01.2020.

Research output: Contribution to journalArticle

Burnett, Lindsey A. ; Cook, Mark ; Shah, Sameer ; Michelle Wong, Ms ; Kado, Deborah M. ; Alperin, Marianna. / Age-associated changes in the mechanical properties of human cadaveric pelvic floor muscles. In: Journal of Biomechanics. 2020 ; Vol. 98.
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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.",
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N2 - 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.

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