Centre Jean-Louis ALIBERT, Institut de recherche Pierre FABRE, Toulouse, France.
Int J Cosmet Sci. 2001 Dec;23(6):353-62. doi: 10.1046/j.0412-5463.2001.00105.x.
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.
我们研究了活体皮肤物理特性各参数随年龄的变化。这些参数通过对一小部分皮肤施加减压并利用 20MHz 扫描回声仪测量其位移，由压力/位移曲线得出。通过将压力/位移曲线拟合到理论模型，我们获得了以下皮肤参数：E，杨氏模量或硬度（以帕斯卡为单位）；sigma(0)，初始应力（以帕斯卡为单位）；以及未恢复能量比（UER），与皮肤非弹性相关的指数。这些参数在力学中用于定义材料的固有物理特性，首次在 206 名 6 个月至 90 岁的男性和女性的前臂掌侧皮肤进行了测量。结果表明，皮肤厚度在成熟前增加，女性在 50-60 岁后减少；杨氏模量 E 随年龄线性增加；自然应力 sigma(0)和非弹性指数 UER 随年龄增长可分为两个阶段。自然应力 sigma(0)在成熟前增加，然后迅速下降。非弹性指数在青春期前下降，青春期后稳定增加。该新方法提供了皮肤物理特性的简单定量评估，揭示了皮肤随年龄增长而变薄、变硬、紧张度和弹性降低。
