Influence of the Biochemical Properties of the Human Skin Fibers on its Mechanical Properties in Vivo According to Age for Two Body Areas: the Forearm and the Thigh

Abstract

Human skin has a stratified and very complex structure with a dense network of collagen and elastic fibers. The skin structure induces associated biochemical and mechanical properties, which are linked and influenced by the fiber's properties. These properties change with age and depend on the body area. In this study, we propose to evaluate the influence of the biomechanical properties of the human skin fibers on its mechanical properties in vivo according to age for two body areas: the forearm and the thigh using two experimental tests: the Diffuse Reflectance Spectroscopy (DRS) and the non-contact impact test. Experimental tests were performed for 42 female volunteers representing two age groups: [20-30] and [45-55] years old. The diffuse reflectance spectroscopy allows measuring the fluorescence intensity of the Advanced Glycation End Products (AGEs) which are markers of aging. Non-contact impact tests were conducted using the WaveSkin ® device. This test generated a Rayleigh wave that spread in the skin. The speed of this wave was measured in seven directions and values of the Young's moduli are deduced. The results of this study show that the mechanical properties of the skin decrease with age due to the degradation of the biochemical properties of skin fibers. This degradation is caused by the accumulation of the AGEs in the skin with age. The intensity of aging effect depends on the body area and on the measurement direction. Aging effect is more important on the thigh and in direction perpendicular to the direction of skin tension i.e., direction of Langer.