Skin ageing: changes of physical properties of human skin in vivo

Abstract

We have investigated in vivo the change with age of various parameters that describe the physical properties of skin. The parameters were derived from pressure/displacement curves obtained by applying reduced pressure to a small area of skin and measuring the resulting displacement by 20 MHz scan echography. By fitting the pressure/displacement curves to a theoretical model, the following skin parameters were obtained: E, Young's modulus or stiffness (in Pascals); sigma(0), the initial stress (in Pascals); and the unrestored energy ratio (UER), an index related to cutaneous non-elasticity. These parameters, which are used in mechanics to define the intrinsic physical characteristics of materials, were measured for the first time on volar forearm skin of 206 male and female subjects, aged between 6 months and 90 years. The results showed that skin thickness increases until maturity and decreases for women over 50-60 years old, Young's modulus E increases linearly with age, and ageing is divided into two phases for natural stress, sigma(0) and the non-elasticity index UER. Natural stress sigma(0) increases until maturity and then rapidly decreases. The non-elasticity index decreases until puberty and steadily increases after puberty. This new procedure provides a simple quantitative assessment of the physical properties of the skin, revealing that the skin becomes thinner, stiffer, less tense and elastic with ageing.

A novel method for visualising and quantifying through-plane skin layer deformations

“…Thus, until now only limited in vivo and in vitro data is available for dynamic shear moduli of (human) skin (Agache et al, 1980;Escoffier et al, 1989;Geerligs et al, 2011a;Holt et al, 2008); shear moduli ranging from 0.2 to 120 kPa have been reported. Shear moduli are typically 1-3 orders of magnitude lower than moduli derived from uni-axial tensile (1-30 MPa), indentation (85-600 kPa), or suction experiments (100-300 MPa) (Diridollou et al, 2001;Geerligs et al, 2011a;McKee et al, 2011;Sanders, 1971Sanders, , 1973. These results clearly illustrate the complex anisotropical material behaviour of skin and the huge scatter in results; further research is clearly needed to fully elucidate the mechanical properties of skin.…”

“…From a mechanical point of view, skin is characterised by (non-)linear viscoelastic, anisotropic material properties similar to those of soft elastomers (Kang and Wu, 2011;Meyers et al, 2008;Ní Annaidh et al, 2012;Oomens et al, 1987). The mechanical properties of skin depend on many factors such as age, anatomical region, strain (rate), and skin hydration level (Diridollou et al, 2001;Gefen, 2011;Gerhardt et al, 2009;Hendriks et al, 2004;Sanders, 1971;Sopher and Gefen, 2011;Wildnauer et al, 1971). Depending on the experimental length scale and contact conditions, contributions of the varying mechanical properties of the individual skin layers (Geerligs et al, 2011a;Hendriks et al, 2006;Holt et al, 2008;Wildnauer et al, 1971) need to be taken into account in the global mechanical response.…”

Strain rate sensitivity of skin tissue under thermomechanical loading

“…Before starting each test, mechanical preconditioning was performed in KHR at 37 • C to ensure a reproducible response to the following test: skin samples were subjected to a displacement controlled sinusoidal excitation with a maximum stretch ratio of 1.05 and frequency of 0.05 Hz. After the preconditioning cycles, the samples were loaded to a stress of 10 kPa to mimic the initial stress of skin in vivo (Diridollou et al 2001). Tensile testing with different loading rates (0.25, 0.5, 1, 2.5, 5 and 10% s −1 ) was performed.…”

Immediate Effects of Different Elastic Tapes Applications on Pain, Isokinetic Muscle Strength, Proprioception and Functional Performance in Patients with Knee Osteoarthritis: Placebo Controlled, Double-Blinded Cross Study

“…Yaşla birlikte cildin sertleştiği ve daha az esnek olduğu bilinmektedir, ayrıca obezite cilde kesme ve dikey basınçları artırır. 28,29 Bu durum elastik bantların ciltte yaratması beklenen traksiyon etkisini engellemiş veya azaltmış olabilir.…”