Biomechanical assessment of photodamage

Background/Aims : Intrinsic aging and photoaging may present different biomechanical properties. Dorsal and volar forearm skin is differently exposed to UV-light. The object was to derive a cutaneous extrinsic aging score (SEAS) representative of UV aging, i.e. the global photoaging corrected for intrinsic aging.
Methods : The Cutometer SM 474 was used for the measurement of skin mechanical properties. 86 healthy Caucasian women were studied. Dorsal and volar forearm skin was measured.
Results : Age related changes consisting of an overall increase in skin extensibility (Uf) and viscoelastic ratio (Uv/Ue) with decreased biologic elasticity (BE) was observed. Differentials in extensibility (Uf) and viscoelastic ration (Uv/Ue) between the volar and the dorsal test sites increase with age.
Conclusions : Biomechanical parameters allow the evaluation of intrinsic aging in the concept of overall photoaging resulting from the combination of environmental damages superimposed to the intrinsic changes.     

Quantitative measurement of desquamation and skin elasticity in diabetic patients

Background/aims: Diabetes mellitus is responsible for many cutaneous alterations. Xerosis and sclerotic change of the skin are the most common findings. Recently non- invasive computerized devices have been developed and used for determining the desquamation rate and measuring the mechanical properties of the skin. Using these devices, the necessity to characterize the conditions of the skin in the healthy as well as the diseased state is increasing. The aim of this study was to compare the elasticity and desquamation rate between the diabetic population and the normal population using non-invasive, objective methods.
Methods: Skin sites of 96 diabetics with normal appearance, were measured for skin elasticity and desquamation rate using the Cutometer^® and visual grading and D-Squame^®– image analysis method, respectively. The values of parameters were compared to values of 83 non-diabetics' results.
Results: There was a significant decrease in skin elasticity (expressed by Uv/Ue and Ur/Uf of the face) and in the value of fine flakes in the diabetics. Although insignificant, the SDI (Scale Density Index) calculated from objective automatic measurement was higher in the diabetics than the control group.
Conclusions: The elasticity of facial skin was decreased in patients with diabetes. Decrease of the fine flakes of the diabetes patients reflect that irritation and xerotic changes are aggravated in skins of diabetic patients. The results indicate the presence of skin elasticity alteration and desquamation with diabetes mellitus. Such non-invasive evaluations of the skin may be useful for evaluating changes in the skin that are associated with diabetes mellitus.     

Contribution of skin biometrology to the diagnosis of the Ehlers–Danlos syndrome in a prospective series of 41 patients

Background/purpose: The diagnosis of the Ehlers–Danlos syndrome (EDS) is primarily clinical. Clinical signs result from modifications of the rheological properties of the skin: thickness, extensibility and hydration. Our main objective was to demonstrate what skin biometry can contribute to the diagnosis and evaluation of the different types of EDS.
Methods: Forty-one patients clinically diagnosed with EDS were paired by age and sex to 41 healthy subjects with no known dermatologic disease, in particular connective tissue diseases. We measured skin thickness, extensibility, hydration and sebum secretion by skin ultrasonography, use of a Cutometer^®, a Corneometer^® and a Sebumeter^®.
Results: The skin is thinner in all three disease types (classical, hypermobility and vascular). It is more extensible only in the classical type, and more hydrated and fatty in the hypermobility type.
Conclusion: Non-invasive measurement of skin thickness and elasticity are quantitative parameters that can be used to better diagnose EDS. Moreover, the sebaceous rate can help to diagnose the hypermobility type whereas the immediate retraction distinguishes the classical form from vascular and hypermobile types.     

Correlation between a Cutometer® and quantitative evaluation using Moire topography in age-related skin elasticity

BACKGROUND/PURPOSE: As aging occurs, our skin gets more wrinkles, becomes drier and loses its elasticity. Validating the evaluation of skin elasticity is especially important, because it is not as visible as other signs of aging such as wrinkles. So it is needed that the method for measuring skin elasticity is able to reflect perception about the change of the skin state. METHODS: Here, the correlation between age and the parameters given by a Cutometer is identified and the main parameters that reflect the decreases in skin elasticity in terms of ages are presented. Also, Moire's system, an evaluation method to quantify the sensory value of viewing, is developed. A five-grade standard of Moire topographic photo scale on the face is used to evaluate the state of skin elasticity and lifting 20- to 61-year-old women. Based on this photo standard, scoring is performed using a five-grade system by three specialists to obtain the consensus score. The score is compared with the result of a Cutometer. RESULTS: Significant negative correlations between age and results of a Cutometer (r=-0.687-0.725), Moire's topography scores (r=-938), were found. Some Cutometer parameters and the decreases in skin elasticity in terms of ages were highly correlated (r=-0.687-0.725). The results from Moire system and flexibility as sensory evaluation also had a very high correlation with age (r=-0.765-0.932). Finally, we have shown the significance of the correlation between the result of a Cutometer and the score of Moire topography (r=0.711). CONCLUSIONS: It is considered that Cutometer parameters R7 and R2 are used as main parameters to assess skin elasticity and aging. And our studies using Moire topography on the face have confirmed that instrumental measurements reflect the decrease in skin elasticity, which is perceived visually.     

Sagging of the cheek is related to skin elasticity, fat mass and mimetic muscle function

Background/purpose: Facial sagging is associated with aging, although the mechanism remains unclear. The aim of this study was to investigate the mechanism of facial sagging by examining the relationship of sagging severity to changes of skin elasticity, fat mass and facial muscle function at the cheek.
Methods: Faces of 108 healthy Japanese female volunteers, aged 20–60 years were photographed at an angle of 45°. Standard scores of sagging severity were established by analyzing the photographs. We examined the correlations of scored sagging levels with skin elasticity measured with a Cutometer MPA 580^®, fat content estimated by bioelectrical impedance analysis and facial muscle function (lip sealing force and occlusal force) in middle-aged female volunteers (30–40 years) with a wide range of sagging scores.
Results: Because the upper, lower and lateral areas in the cheek may show severe sagging, a six-grade score of sagging severity was separately established for each area. Each score was significantly correlated positively with age (20–60 years). In middle-aged volunteers, the sagging scores in all three areas of the cheek were significantly and negatively associated with skin elasticity. Body fat percentage was significantly and positively correlated with the sagging scores in the lower and lateral areas, although the correlation was only weakly positive in the upper area. Mimetic muscle function, measured in terms of lip sealing pressure, was significantly and negatively correlated with the sagging score only at the upper area of the cheek, but masticatory muscle function, measured in terms of occlusal force pressure, was not associated with the sagging score.
Conclusions: Sagging may be associated with the reduction of skin elasticity and mimetic muscle function and increase of fat mass, but the relationships are different in different areas of the cheek.     

Dermal fluid translocation is an important determinant of the diurnal variation in human skin thickness

BACKGROUND: Ultrasonography has been used as a non-invasive approach to measure skin thickness. To date there have been no studies on diurnal variations in skin thickness. OBJECTIVES: To evaluate diurnal variations in skin thickness and to compare these with corresponding echogenicity and skin elasticity. METHODS: Measurements by ultrasonography B-mode and by Cutometer SEM 575 were carried out in the morning and in the afternoon on 20 men and 20 women (mean age 30 years) on three areas of the face (forehead, corner of the eye and cheek), the forearm and the upper arm, and the flank, thigh and calf. RESULTS: From the morning to the afternoon, the skin thickness in both sexes significantly decreased on three areas of the face, the forearm and the upper arm, but significantly increased on the thigh and calf. In parallel, the echogenicity significantly increased from the morning to the afternoon on the three areas of the face, the forearm and the upper arm, but decreased significantly on the thigh and calf. Measurements of mechanical properties at four sites demonstrated that from the morning to the afternoon, the major parameters of skin elasticity Ue* and Uf* increased significantly in both sexes on two areas of the face and slightly on the forearm, but decreased significantly on the calf. CONCLUSIONS: The diurnal profiles of skin thickness and skin elasticity in the upper half of the body are the reverse of those in the lower half of the body. These findings suggest that shifts of dermal fluid from the face to the leg by gravity during the day cause the diurnal variation in skin thickness.     

Skin biomechanical properties: in vivo evaluation of influence of age and body site by a non-invasive method

Background/aims: Biomechanical properties of the skin are evaluated in vivo by torsion or extension methods. We assessed their modifications as function of age, probe diameter and regional body site.
Methods: For measuring skin extensibility (or traction), we used a non-invasive suction device on a total of 37 volunteers, consisting of (A) 14 younger women (30.1±7.6 years) and (B) 23 older women (60.2±6.5 years). Measurements were performed on three different areas with 4 different probe diameters. The parameters used were ( U _E) extensibility; ( U _V) plasticity; ( U _R) tonicity; ( U _R U _E) elasticity; the difference between the lowest point of the last curve (5th) and that of the 1st is the fatiguability. Concurrently, we measured on each volunteer the microdepressionary network (mDN) length.
Results: Generally, tonicity, extensibility and elasticity decreased; fatiguability increased and plasticity stayed the same; all of these factors apply regardless of age. Results are more homogenous on the volar face of the forearm and with 2, 4 and 6 mm probe diameters. As a general trend, mDN length decreases with age.
Conclusions: The knowledge of this variation is important in interpreting the results obtained after product application. Standardisation of measures with the 2-mm probe will allow product efficacy determination and the comparison of different products.     

Characterization of the mechanical properties of a dermal equivalent compared with human skin in vivo by indentation and static friction tests

Background/aims: The study of changes in skin structure with age is becoming all the more important with the increase in life. The atrophy that occurs during aging is accompanied by more profound changes, with a loss of organization within the elastic collagen network and alterations in the basal elements. The aim of this study is to present a method to determine the mechanical properties of total human skin in vivo compared with dermal equivalents (DEs) using indentation and static friction tests.
Methods: A new bio-tribometer working at a low contact pressure for the characterization the mechanical properties of the skin has been developed. This device, based on indentation and static friction tests, also allows to characterize the skin in vivo and reconstructed DEs in a wide range of light contact forces, stress and strain.
Results: This original bio-tribometer shows the ability to assess the skin elasticity and friction force in a wide range of light normal load (0.5–2 g) and low contact pressure (0.5–2 kPa). The results obtained by this approach show identical values of the Young's modulus E ^* and the shear modulus G ^* of six DEs obtained from a 62-year-old subject ( E ^*=8.5±1.74 kPa and G ^*=3.3±0.46 kPa) and in vivo total skin of 20 subjects aged 55 to 70 years ( E ^*=8.3±2.1 kPa, G ^*=2.8±0.8 kpa).     

Effect of dermal thickness, tissue composition, and body site on skin biomechanical properties

BACKGROUND/PURPOSE: Quantitative measurement of skin biomechanical properties has been used effectively in the investigation of physiological changes in tissue structure and function and to determine treatment efficacy. As the methods are applied to new questions, tissue characteristics that may influence the resultant biomechanical properties are important considerations in the research design. For certain applications, variables such as dermal thickness and subdermal tissue composition, as well as age and/or solar exposure, may influence the skin biomechanics. METHODS: We determined the influence of dermal thickness, tissue composition, and age on the skin biomechanical properties at the shoulder, thigh, and calf among 30 healthy females. We compared two devices, the Biomechanical Tissue Characterization System and the Cutometer SEM 575 Skin Elasticity Meter , to determine the effect of tissue sampling size. Dermal thickness was measured with 20 MHz ultrasound (Dermascan C) and tissue composition was inferred from anthropomorphic data. RESULTS: Skin thickness was significantly correlated with stiffness, energy absorption, and U(r)/U(f) for the shoulder. Body mass index (BMI) was significantly correlated with stiffness (negative correlation), energy absorption (positive), and skin thickness (negative) for the shoulder. Significant differences across body sites were observed. The calf was significantly different from the thigh and shoulders for all parameters (P<0.05, one-way anova). The calf had significantly lower laxity, laxity%, elastic deformation, energy absorption, elasticity, elasticity %, U(r), U(f), and U(r)/U(f) and significantly higher stiffness compared with the thighs and shoulders. sites. The thigh and shoulder sites were significantly different for all parameters except U(r)/U(f), elasticity %, laxity%, and stiffness. The dominant and non-dominant sides were significantly different. The dominant side (right for 90% of the subjects) had increased stiffness and decreased energy absorption (tissue softness, compliance) compared with the left side. A significant (P< or =0.02) negative relationship with age was seen for all biomechanical measures except stiffness at the shoulder. For the thigh and calf sites, significant negative correlations with age were found for elasticity %, U(r), and U(r)/U(f). Age and skin thickness were not correlated in this population. Skin thickness and age influenced the energy absorption at the shoulder site. The biological elasticity at the calf site could be predicted by age and BMI. The biological activity at the thigh site could be predicted by skin thickness and BMI. CONCLUSIONS: Significant regional variations in biomechanical properties and dominant side effects were observed. The biomechanical properties were significantly influenced by age. Certain properties varied with dermal thickness and tissue composition. The parameters were well correlated between the two instruments. The Cutometer, with its smaller aperture, was found to be more sensitive to age relationships.     

In vivo skin elasticity of 22 anatomical sites

Background/aims: Regional anatomical variations in bio-mechanical properties of skin were not mapped systematically in the past, despite the obvious clinical variation of this function. The object was to describe variations in skin distensibility and elasticity by the use of a suction chamber device.
Methods: 22 different anatomical sites were measured in 25 healthy volunteers aged 5-72 years. Anatomical sites were numbered systematically from the head toward the foot according to a vertical principle as a part of the study design.
Results: A systematic and vertically oriented decrease of distensibility and hysteresis from the head toward the foot was observed with a gradual increase of skin stiffness toward the ground. Skin elasticity decreased significantly with age. Acral female skin was more easily distended than male skin.
Conclusions: The vertical gradient of skin distensibility was described for the first time. This appears a prerequisite to resist the hydrostatic pressure and influences of gravity. The findings may have important implications in leg ulcer and gravitational syndrome.     

Measurement of skin elasticity on the foot

BACKGROUND/PURPOSE: The Cutometer 580 MPA is a device that is designed to measure the viscoelastic properties of skin in response to the application of negative pressure. The aim of this study was to test the Cutometer 580 MPA for the repeatable, quantitative measurement of the specific indices of elasticity of pedal skin. The device was used to measure and compare these indices at weight-bearing and non-weight-bearing skin sites on the foot. METHODS: The relationship between the pressure application and skin displacement was determined. The inter- and intra-tester repeatability was tested. These series of experiments were conducted on 20 individuals. Data were then collected from a group of 87 healthy people for the measurement of elasticity, viscoelasticity and plasticity on several sites on the foot. The possible influences of physiological variables such as age and sex on the indices of elasticity were analysed. RESULTS: The Hookian elastic behaviour of the skin was confirmed. The pressure application did not remain constant during the collection of displacement data, resulting in an error in these readings of between 1.71% and 3.73%. Intra-tester and variability was minimal (CV<7%). The elasticity, viscoelasticity and plasticity indices were significantly greater (P<0.001) in dorsal skin compared with skin from medial longitudinal arch (MLA) and plantar aspect of the third metatarsophalangeal joint (PMA) sites. There was a negative correlation between age and elasticity on the dorsum and MLA skin sites (r=-0.216 and -0.261, respectively). Female skin exhibited greater plasticity than male skin on all three sites on the foot (P<0.05). CONCLUSION: Under well-controlled conditions, the Cutometer 580 MPA has the ability to measure accurately the viscoelastic properties of pedal skin. Such non-invasive measurements may be useful for the evaluation of changes in the skin in response to therapeutic interventions and for monitoring the progression of dermatological conditions associated with the foot.     

Skin–textile friction and skin elasticity in young and aged persons

Background/purpose: The mechanical properties of human skin are known to change with ageing, rendering skin less resistant to friction and shear forces, as well as more vulnerable to wounds. Until now, only few and contradictory results on the age-dependent friction properties of skin have been reported. This study has investigated in detail the influence of age on the friction of human skin against textiles.
Methods: In vivo skin-friction measurements on a force plate were combined with skin analyses concerning elasticity, hydration, pH value and sebum content. Thirty-two young and 28 aged persons rubbed their volar forearm in a reciprocating motion against various textiles on the force plate, using defined normal loads and sliding velocities, representing clinically relevant contact conditions.
Results: Mean friction coefficients ranged from 0.30 ± 0.04 (polytetrafluoroethylene) to 0.43 ± 0.04 (cotton/polyester). No significant differences in the friction properties of skin were found between the age groups despite skin elasticity being significantly lower in the aged persons. Skin hydration was significantly higher in the elderly, whereas no significant differences were observed in either skin pH value or sebum content.
Conclusion: Adhesion is usually assumed to be the dominant factor in skin friction, but our observations imply that deformation is also an important factor in the friction of aged skin. In the elderly, lower skin elasticity and skin turgor are associated with more pronounced skin tissue displacements and greater shear forces during frictional contact, emphasizing the importance of friction reduction in wound-prevention programmes.     

Tissue viability imaging: mapping skin erythema

Background: Tissue Viability Imaging (TiVi) is an emerging bioengineering technology intended for two-dimensional mapping of skin erythema and blanching. Before TiVi can be effectively used in studies of diseased or damaged skin, the variability in normal skin red blood cell concentration (RBC_conc) requires evaluation.
Objective: To demonstrate how TiVi maps spatial and temporal variations in normal skin RBC_conc at the dorsal side of the hand at rest and during post-occlusive hyperemia.
Methods: Short-term and day-to-day variations in skin RBC_conc were quantified at the dorsal side of the hand in four healthy volunteers at rest. In a separate study, the increase in skin RBC_conc was recorded during post-occlusive hyperemia.
Results: A lower skin RBC_conc (179–184 TiVi units) was observed at the back of the hand and base of the thumb compared with areas adjacent to the nailfoldfold region of the fingers (190–213 TiVi units). The short-term variation (within 70 s) was <2% in all areas of the dorsal side of the hand, while day-to-day variations were in the range 5–7% in the back of the hand and up to 10% in areas adjacent to the nailfold region. In the post-occlusive hyperemia phase, up to a 60% increase in skin RBC_conc was observed in the early part of the reactive hyperemia phase. This increase in skin RBC_conc successively decreased but remained about 18% above the pre-occlusion level after 30 min.
Conclusion: Establishment of healthy skin RBC_conc reference values is important for the design of versatile test procedures for assessment of skin damage caused by vibration tools, chemical exposure or peripheral vascular disease.     

An in vivo study of the mechanical properties of facial skin and influence of aging using digital image speckle correlation

Background/purpose: The skin on the face is directly attached to the muscle through the superficial musculoaponeurotic system. We show that this can be used to probe skin mechanical properties, in vivo , using, digital image speckle correlation (DISC), a technique that measures the intrinsic cutaneous pore structure displacement following a natural facial deformation.
Methods: We take a series of images, which are then analyzed with DISC to create a displacement vector diagram, from which we can obtain spatially resolved information regarding facial deformation. We then studied the functional form of the displacement as a function of age, location on the face, and skin treatment. Finally, through DISC vector field analysis we investigate the mechanism of wrinkle formation.
Results: We first show that facial skin displacement follows the direction of muscular movement and reflects the magnitude of the applied forces. Using DISC vector field analysis, we find that as the skin ages the distribution of forces becomes more condensed, with a marked spatial asymmetry. Analysis of the data, in the perioral region, we find that the skin elasticity decreases exponentially with age, with a decay constant of approximately 32 years. Similar results, but with a larger amplitude, were also found for the periorbital region. Finally, DISC vector field analysis also shows that the location of maximal stress correlated with the location of existing facial wrinkles.
Conclusion: The DISC method, as a non-contact technique, is a potential clinical research tool for the diagnosis of facial skin condition and underlying muscular activity. We demonstrate how these factors can be used to monitor the effects of aging, formation of wrinkles, and the efficacy of topical applications of skin creams.     

Intrinsic, solar and sunbed-induced skin aging measured in vivo by multiphoton laser tomography and biophysical methods

Background: Skin aging is accelerated by extrinsic factors, particularly actinic damage. Over the last decades, both clinical and pathological differences between intrinsic and actinic aging have been characterized. In this work, we aimed at quantifying skin aging by non-invasive in vivo methods.
Methods: Young healthy volunteers using indoor tanning facilities and aged people were compared with appropriate controls by measurements of skin elasticity with the Cutometer and the Reviscometer and by semi-quantitative evaluation of the dermal matrix composition by the multiphoton laser tomograph DermaInspect.
Results: We found differences between the sun-protected volar forearm and the dorsal side as well as between young and old test persons with all three methods. No significant differences were found between the skin of indoor-tanned test persons and control. Also, gender had no influence on the severity of skin aging.
Conclusion: The most consistent results were obtained with the DermaInspect. The considerable inter-individual variation due to the cross-sectional design of the study may have disguised the factual skin damage caused by tanning beds.     

Effects of lipid nanocarriers on the performance of topical vehicles in vivo

Background/aims  Nanocarrier systems have been extensively studied for their suitability in personal care formulations. Theoretically, they could enhance skin delivery of active compounds, thereby improving in vivo efficacy of the products. As such the aim of this study was to evaluate the effect of a lipid nanocarrier (LNC) system loaded with tocopheryl acetate (TA) on the hydration, biomechanical properties, and antioxidant capacity of human skin, when used in two different vehicles, and compare it with a non-LNC formulation.
Methods  TA-loaded lipid nanocarriers (TA-LNCs) were produced by the phase inversion method, using physiological lipids and purified by ultra-centrifugation. They were incorporated into a hydrophilic gel and foam, and their performance compared with a saturated TA solution in silicon oil. Skin hydration and biomechanical properties were measured by means of a corneometer and a cutometer, respectively, while a high-resolution spectrophotometer was used to assess skin redness after stimulation by methyl nicotinate in a micro-inflammatory test. Both short-term (3 h) and long-term trials (4 weeks) were performed.
Results  The results confirmed that the LNCs enhanced skin hydration in both studies, while skin viscoelastic parameters remained practically unchanged during the 4-week study. The antioxidant assessment failed to show significant difference between the test sites.
Conclusions  TA-loaded LNCs exhibited the ability to enhance skin hydration, while their effect on skin biomechanical properties and on antioxidant efficacy could not be statistically proved.     

Cellulite and skin ageing: is there any interaction?

Objective  This study aimed to identify the characteristics of cellulite in women of different age and to appreciate whether cellulite could interfere with skin ageing or not.
Methods  94 healthy females, divided into three age groups (21–30yrs; 31–40yrs; 51–60yrs) and two grade groups of cellulite (grade 2; grade 0 or control group), were investigated using non invasive techniques. The "orange peel appearance" was quantified by measuring the shadowed surfaces under low angle light. The biomechanichal properties were measured (extensibility-retractability-elasticity). The thicknesses of the skin structures were also evaluated using ultrasound. Echogenicity of the dermis was recorded and dermis density determined in two bands (superficial and low dermis).
Results  In grade 2, the shadowed surfaces are significantly different according to age; i.e. smaller and more numerous after age of 30; the total skin thickness including hypodermis is increased of about 30% irrespective to age, compared to control group.
The biomechanical properties of the skin are significantly modified as age increases without any grade effect. In grade 2, retractability and elasticity parameters are altered from age 30 whilst only from age 50 in the control group. Echogenicities of the superficial and deep dermis also decrease from age 30 and become significantly lower than the ones of grade 0.
Conclusion  Population with cellulite presents earlier skin ageing characteristics than the control population. Two sub-populations may exist: the under 30 age with large dimpled surfaces, normal biomechanical and density properties; and the over 30 age with smaller and numerous dimpled surfaces and already altered dermis properties. This premature skin ageing should be prevented accordingly.     

Two possible classifications of facial skin type by two parameters in Korean women: sebum excretion rate (SER) and skin surface relief (SSR)

Background/alms: Worldwide there are many skin care and makeup products intended to maintain good appearance or youthful skin. However consumers don't know which products are suitable for their skin because they don't know their skin type exactly. To solve this problem, this study suggests two possible classifications of facial skin type by using simple methods.
Methods: In 662 healthy volunteers, sebum excretion rate (SER) on the forehead and cheek, and skin surface patterns on the cheek were examined by using Sebutape® and skin replica, respectively.
Results: The measured SER values from the forehead were 0.06-4.56 ng/cm²/min and those from the cheek were 0.04-3.80 ng/cm²/min. From these data, five facial skin types were classified by SER: low SER type, medium SER type, high SER type, combination-1 SER type, and combination-2 SER type. Twelve facial skin types were also classified; they were determined by star formation (SF), primary lines (PL), secondary lines (SL) and pore size from magnified skin surface relief (SSR) of the cheek.
Conclusions: From this study, we suggest new classifications of skin types by SER and SSR. The SER and the parameters of skin surface texture (SF, PL, and SL) decreased with age and the pore size increased with age. Although these methods did not classify facial skin types perfectly, we were able to check consumer's facial skin types simply and more quickly.     

皮肤共振传导时间的测量及其意义

皮肤的生物物理特性是由皮肤局部及机体系统的生物功能所决定。皮肤弹性的改变系多种因素所导致真皮胶原或/和弹力纤维的变化而引起。这些变化可体现在皮肤共振传导时间的改变。通过测量同一部位不同方向共振传导时间,不仅能判断皮肤弹性的变化,同时还可推测哪个方向胶原或/和弹力纤维发生了改变。此外,本测量方法简便。因此,在判断皮肤老化(光老化和自然老化)程度和评估改善皮肤弹性产品的效果时,测量皮肤共振传导时间是值得一试的手段之一。